Long Answer Questions A LEVEL BIOLOGY

7/21/2019 Long Answer Questions A LEVEL BIOLOGY

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Unit 1


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Microscopes

Prokaryotic cells

Cell fractionation

Scientists use optical microscopes and transmissionelectron microscopes (TEMs) toinvestigate cell structure. Explain the advantages andthe limitations of using a TEM

to investigate cell structure.

Advantages:1 Small objects can be seen;

2 TEM has high resolution;3 Wavelength of electrons shorter;imitations:! "annot loo# at living cells;$ Must be in a vacuum;% Must cut section & thin s'ecimen;( )re'aration ma* create artefact

+ ,oes not 'roduce colour image;

The structure of a cholera bacterium is different from thestructure of an epithelial cell from the small intestine.Describe how the structure of a cholera bacterium is

Different.

1 "holera bacterium is 'ro#ar*ote;2 ,oes not have a nucleus&nuclear envelo'e& has ,-A freein c*to'lasm&has loo' of ,-A;3 and ! An* t.o from-o membrane/bound organelles&no mitochondria & no golgi&no endo'lasmic reticulum&etc;$ Small ribosomes onl*;

% and ( An* t.o from"a'sule&flagellum&'lasmid & cell .all&etc;

Measuring the size of an object under a

microscope

Measure with an eyepiece graticule

Calibrate with the stage mcirometer (an object of a

known size)

Repeat and calculate an aerage

Explain the advantages and limitations of using a transmission

electron microscope to study cells.

1 TEM uses (beam of) electrons;

2 These have short avelength;! "llo high resolution#greater resolution#"llo more detail to

be seen#greater useful magnification;$ Electrons scattered (by molecules in air);% &acuum established;' annot examine living cells;

*ots of preparation#procedures used in preparing specimens# fixing#staining#sectioning;+ May alter appearance#result in artefacts;

Starting with some lettuce leaves,describe how you would obtain a sample of

undamaged chloroplasts. se your

knowledge of cell fractionation and

ultracentrifugation to answer this

!uestion.

1! Chop up (accept any reference to crude

breaking up)" #! Cold" (reduces

enzyme actiity)

$! %u&ered solution" (preents p' a&ecting

enzymes)! sotonic * same water potential" (preents

osmosis and possible lysis or shrinkage of

organelles)

+! ,ilter and centrifuge -ltrate"

.! Centrifuge supernatant"

/! 0t higher speed"

! Chloroplasts in (second) pellet"


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2rokaryotic cells

and fractionation

The bacteria in the intestine are pro,aryotic cells. The

epithelial cells hich line the small intestine are eu,aryoticcells. -escribe the ays in hich pro,aryotic cells and

eu,aryotic cells differ

1 ro,aryotic cells do not have a nucleus # have genetic

material in cytoplasm;

2 -/" in loop # ring;! /ot associated ith proteins # do not have chromosomes #

chromatin # do not divide by mitosis;

$ 0maller ribosomes;

% /o membranebound organelles;

' 0uch as mitochondria # lysosomes # endoplasmic

reticulum # olgi # chloroplasts;

ro,aryotic cells may have mesosomes;

+ ro,aryotic cells smaller;

3 May be enclosed by capsule;

4o pro,aryotic cell is the same and different to a eu,aryotic cell

cytoplasm;

ribosomes;

phospholipid membranes # cell membrane # semipermeable

membrane; 2 max

(accept folded membrane for two marks)

(ii)

(it = bacterium)

cell all;

capsule;

flagellum;mesosome;

no nucleus # nuclear membrane # -/" free;

no mitochondria;

(accept no membrane-bound organelles if neither nucleus

nor mitochondria mark scored)

no microvilli;

no olgi;

no E5;

60#smaller ribosomes;

arts of the pro,aryotic cell

cell (surface) membrane7

regulates entry#exit#selectively permeable;

8mesosome7

respiration#cell division;

cell all7(mechanical) protection#prevents (osmotic) lysis;

-slime layer#capsule7

protection (against e.g. antibiotics);

Eflagellum7

movement of cell;

9 -/" molecule#bacterial chromosome7

genetic information;

ive two factors hich affect the ability ofbacteria to cause a disease.

pathogenicity # toxicity of products;

site of infection;

invasiveness;


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Microscopes

,ractionation

*abelled antibodies and an electron microscope can be used

to produce images locating proteins on the surface oforganelles7 but cannot be used to observe cross bridge

cycling in muscle cells. Explain hy.

1. e.m. gives high resolution;

2. due to short avelength of electrons;

!. antibodies attach specifically to target proteins;$. gold particles are electron dense;

%. electrons must pass through a vacuum;

'. material must be dead # fixed for e.m.;

. crossbridge cycling re:uires living cells #

metabolism # named

aspecte.g. "T synthesis;

0tarting ith some lettuce leaves7 describe hoyou ould obtain a sample of undamaged

chloroplasts. se your ,noledge of cell

fractionation and ultracentrifugation to

anser this :uestion.

1. hop up (accept any reference to crude

brea,ing up);

2. old;

!. 8uffer solution;

$.


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2rokaryotic cells

and iruses and

microscopes

-escribe the ays in hich pro,aryotic cells and eu,aryotic

cells differ

ro,aryotic cells do not have a nucleus # have genetic

materialin cytoplasm;

-/" in loop # ring;/ot associated ith proteins # do not have chromosomes #

chromatin # do not divide by mitosis;

0maller ribosomes;/o membranebound organelles;0uch as mitochondria # lysosomes # endoplasmic reticulum #

olgi # chloroplasts;

ro,aryotic cells may have mesosomes;

ro,aryotic cells smaller;May be enclosed by capsule;

-efine resolving poer and state hy it is bteter forelectron microscopes than light

(i) "bility to distinguish points(close together); 1

(ii) Electrons have a

shorter avelength;

Explain ho viruses cause damage to cells.

uses # brea,s up # digests host nuclear # geneticmaterial (allow references

made to #$A %&$A instead of nuclear %genetic)'

virus -/" # genetic material inserted into hosts -/" #

chromosome

# genetic material;

host cells amino acids are used to synthesi@e viralproteins;

cell lysis;

by en@yme (produced by expressing a virus gene);

toxin production;


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Cell

membranes

Describe the fluid-mosaic structure of a cell surface

membrane.(5)

hospholipids and proteins;

hospholipid bilayer;

"rrangement of phospholipid molecules ATails to

tailsB;

A9loatingB(protein) molecules # molecules can move in

membrane;


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Cell

membrane

-escribe the structure of a cell membrane.

-ouble layer of phospholipid molecules;

-etail of arrangement of phospholipids;


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Cell

membranes

-escribe ho proteins are arranged in a plasma membrane

and the part they play in transporting substances into and outof cells.

1 0ome proteins pass right through membrane;

2 0ome proteins associated ith one layer;

!


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Cell

membranes

-escribe ho proteins are arranged in a plasma

membrane and the part they play in transporting

substances into and out of cells.

1 0ome proteins pass right through membrane;


!


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+arrier proteins involved ith facilitated diffusion;

Cell

membranes

-escribe ho proteins are arranged in a plasma

membrane and the part they play in transportingsubstances into and out of cells.

0ome proteins pass right through membrane;


!


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5nzymes

Explain ho pepsin is inactivated by the high p4 in

the small intestine.

4igh p4 denatures en@yme# alters charge on active

site;8rea,s bonds;

"lters tertiary structure of en@yme molecule;hanges shape of active site;

"ctive site can no longer bind ith# form E0complexes ith# is no

longer complementary to substrate;


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"nzymes


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"nzymes

xplain what happens to an en!yme molecule when it is

denatured by high temperature.

orrectly named bonds bro,en # ater removed;

tertiary # globular shape of en@yme changed;

shape of active site affected;

Temperature has a mar,ed effect on blood p4. "t ! Gblood plasma has a p4 of .$ but at a temperature of 2% G7

the p4 is '.3.


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"nzymes

Explain ho a substrate is bro,en don by the en@yme.

0ubstrate enters active site;

omplimentary shapes # *oc, and Hey;

(8inding) to form en@ymesubstrate complex;

*oering of activation energy;

onformational # shape change;

8rea,ing of bonds in substrate;

roducts no longer fit active site and so are released;

se your ,noledge of the tertiary structure of en@ymes to

explain ho a non competitive inhibitor could reduce the

rate of an en@yme controlled reaction.


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"nzymes

Explain ho the shape of an en@yme molecule is related to

its function.

specific !- tertiary structure#shape;

substrate complementary shape; (re+ect same shape)

substrate (can bind) to active site# can fit into each active

site;

decreasing the p4 affects carbohydrase activity.

(decrease in p4) increases 4Iions#protons;

% attach#attracted to amino acids;

' hydrogen#ionic bonds disrupted#bro,en;

denatures en@yme # changes tertiary structure;

+ changes shape#charge of active site;

3 active site#en@yme unable to combine#fit ith

starch#en@ymesubstrate

complex no longer able to form decreases rate of brea,donof starch#rate of reaction #carbohydrase activity;


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"nzymes

-escribe ho molecular shape is important in explaining the

ay in hich en@ymes may be affected by inhibitors.

"ctive site (of en@yme) has particular shape;

(


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5nzymes

-escribe ho molecular shape is important in explaining the

ay in hich en@ymes may be affected by inhibitors.(')

1 "ctive site (of en@yme) has particular shape;

2 (


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5nzymes

-escribe ho the condensation reaction can be catalysed by

an en@yme.

en@yme has an active site;

ith a complementary shape to the substrate molecules;

en@ymesubstrate complex formed;

loering the (activation) energy for the reaction;

glycosidic bond formed#bringing together hydroxyl

groups#ater

molecule removed;

products leave the active site;

en@yme unchanged;

Explain ho substrates are bro,en don by the en@yme.

0ubstrate enters active site;

omplimentary shapes # *oc, and Hey;

(8inding) to form en@ymesubstrate complex;

*oering of activation energy;

onformational # shape change;

8rea,ing of bonds in substrate;

roducts no longer fit active site and so are released;

Explain ho amylase ma,es it possible for starch to be

digested at body temperature.

"ctivation energy reduced;

starch attached to active site # formation of en@ymesubstrate

complex;

less energy re:uired to bring (substrate) molecules together# to brea, bonds;

reaction occurs in small(er) steps;

change in shape of en@yme molecule (induced fit) brings

molecules

together # allos bonds to brea, # causes overlapping ofelectron

orbits of substrates.

-escribe and explain ho an increase in temperature affects

the rate of an en@yme controlled reaction.

Temperature

5ate of reaction increases;


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"ctive site altered#substrate cannot bind#fit#

5nzymes

Many reactions ta,e place in living cells at temperatures far

loer than those re:uired for the same reactions in a

laboratory. Explain ho en@ymes enable this to happen.

loers activation energy;

relevant mechanism e! g! brings molecules close together %reaction in smaller

steps % change in charge distribution % proton donation or

acceptance % induced

fit ensuring substrates brought in correct seuence'

including relevant reference to active site;

Expalin ho decreasing the p4 affects carbohydrase activity.

(decrease in p4) increases 4Iions#protons;

% attach#attracted to amino acids;

' hydrogen#ionic bonds disrupted#bro,en;

denatures en@yme # changes tertiary structure;

+ changes shape#charge of active site;

3 active site#en@yme unable to combine#fit ith

starch#en@ymesubstrate

complex no longer able to form;

decreases rate of brea,don ofstarch#rate of reaction

#carbohydrase activity;

Explain ho the shape of an en@yme molecule is

related to its function.

specific !- tertiary structure#shape;

substrate complementary shape; (re+ect same shape)

substrate (can bind) to active site# can fit into each

active site;


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%iological

molecules

Describe a chemical test you could carry out to show that

a piece of coconut contains lipids.()

(rush in) ethanol # alcohol;

"dd (to) ater (3rder of adding is critical for this point);

Emulsion # hite colour

Describe how you would use a biochemical test to show

that a sample contained reducing sugar.(,)

8enedictBs and heat;

reen # yello # orange # red # bron

#o not credit unualified references to water baths

Describe how the se+uence of amino acids in part of

a protein from a persons ears could enable this

protein to act as an en!yme inhibitor.(6)

1 0e:uence of amino acids gives shape;

2 This is tertiary structure;

! 4as similar shape to substrate;

$ 9its # competes for active site;

% 9its at site other than active site;

' -istorting active site;

Therefore substrate ill not fit (active site);

Describe how you would use a biochemical test to show

that a solution contained protein.

8iuret # al,ali I copper sulphate;

*ilac#purple#mauve#violet;

xplain what is meant by a polymer.

(Molecule) made up of many identical#similar

molecules#monomers#

subunits;

Explain ho proteins are suited for their roles as receptor

molecules.

Many different sorts of proteins;

-ifferent primary structures#se:uences of amino acids;

Tertiary structure;

0hape; alloing formation of receptor#binding site#site into

hich

substance#substrate fits;


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#ipid$protein carbs

?ith reference to named parts of the diagram7 explain the

difference beteen the terms=

triglyceride andphospholipid;

hospholipid has (one) phosphate # hosphoric acid;2

replacing fatty acid;

saturated and unsaturated.

0aturated F all valencies of filled # saturated ith

hydrogen # all (F)

single bonds # no double bonds;

fatty acid 1 is saturated#fatty acids 2 and ! are unsaturated;

-escribe ho a saturated fatty acid differs in molecular

structure from an unsaturated fatty acid.

absence of a double bond;

in the (hydrocarbon) chain;

unable to accept more hydrogen # saturated ith hydrogen;

Explain ho the structure of fibrous proteins is related to

their functions.

*ong chains of aa;

9olding of chain into a coil # folds # helix # pleated sheet;

"ssociation of several polypeptide chains together;

9ormation of fibres # sheets explained;

2

4 bonds # -isulphide bonding (,n context);

9ibres provide strength (and flexibility);

0heets provide flexibility;

Example e.g. ,eratin in hair7 collagen in bone; (4567 be in

context)


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%iological

molecules

-escribe the structure of an amino acid molecule and

explain ho amino acids lin, together.

1 "mino acid based on carbon ith four groups attached;

2 "mino# /42and carboxyl # 4;

! 5group# side chain I hydrogen;$ 5group differs from one amino acid to another;

% "mino acids >oined by condensation;

' 8ond formed beteen /42and 4;


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%iochemical tests

-escribe ho you could use 8enedictBs reagent

to test a urine sample for the presence of

glucose.

"dd (8enedictBs) reagent (to urine sample) and heat #

heat the mixture;

red# bron# orange# green# yello;

describe a further biochemical test to find out ifsubstance D is a nonreducing sugar.

heat ith acid7 then neutralise # hydrolyse using

en@yme;

(heat) ith 8enedictBs (solution);

-escribe ho you ould use a biochemical test to

sho that a solution contained protei

8iuret # al,ali I copper sulphate;

*ilac#purple#mauve#violet;

-escribe a chemical test you could carry out to sho

that a piece of coconut contains lipids.

(rush in) ethanol # alcohol;

"dd (to) ater (3rder of adding is critical for thispoint);

Emulsion # hite colour;

-escribe ho standard solutions could be used

to estimate the concentration of reducing

sugar in the samples.

0ugar solutions of ,non # specificconcentrations;

Test each concentration ith 8enedictBs

solution;

use e:ual volumes of solutions # variablescontrolled;

Method of comparison7 e.g. compare colours7

mass of precipitate.


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Cholera

Explain ho the effects of diarrhoea on the body can

be treated.

oral rehydration therapy#5T;

replaces lost ater and salts;

5

drin,ing large amounts of ater;

ith salts#minerals;

0uggest hy the cholera exotoxin is specific to the

epithelial cells of the small intestine.

receptor # proteins on membrane;

complementary shape of exotoxin;

-escribe the difference beteen an endotoxin and an

exotoxin.

endotoxins produced from the brea,don of bacteria

(cell alls);

(allow burst % l1se / do not allow decompose)

exotoxins secreted # released (from living cells) (notproduced);

endotoxins are lipopolysaccharides;

exotoxins are protein;

Explain ho an oral rehydration solution (50)

replaces ater lost by diarrhoea


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Cholera

The structure of a cholera bacterium is different from the

structure of an epithelial cell from the small intestine.

-escribe ho the structure of a cholera bacterium is

different.

holera bacterium is pro,aryote;

-oes not have a nucleus#nuclear envelope# has -/" free in

cytoplasm#has loop of -/";! and $ "ny to from

/o membranebound organelles#no mitochondria # no

golgi#no

endoplasmic reticulum#etc;4aximum of . marks for points and 8!

%0mall ribosomes only;

' and "ny to from

apsule#flagellum#plasmid # cell all#etc;

6ral rehydration solutions (6R7) are used totreat diarrhoeal disease! 8hat does an 6R7consist of and how does it work9(+)

10 "ontains glucose&starch& carboh*drate & sugar;20 Sodium&salt;30 "o/trans'ort & s*m'ort;!0 Sodium and glucose ta#en u' from lumen;$0 o.ers .ater 'otential in cells& increases .ater'otential gradient;%0 Water ta#en u' b* osmosis

ive twoays in hich pathogens can cause disease

hen they enter the body of their host.

-amage#destruction of cells#tissues;

roduction of toxins;


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3igestion

Describe the role of the enzmes of the digestive sstem

in the complete brea!down of starch.

Am*lase;Starch to maltose:Maltase;Maltose to glucose;*drol*sis;

4f gl*cosidic bond;

Describe the processes involved in the absorption of the

products of starch digestion.

5lucose moves in .ith sodium into e'ithelial cell;6ia carrier&channel 'rotein&s*m'ort;Sodium removed from e'ithelial cell b* activetrans'ort&sodium/'otassium 'um';7nto blood;Maintaining lo. concentration of sodium in e'ithelial cell &maintaining sodium concentration gradient bet.een lumenand e'ithelial cell;5lucose moves into blood;

8* facilitated diffusion;

Describe and explain the roles of diffusion" facilitated diffusion

and acti&e transport in the absorption of digested food by the

ileum.

-iffusionmovement along # don concentration gradient;monoglycerides # micelles#fatty acids move into epithelial cells;

monoglycerides move from epithelium into blood;

chylomicrons move into lacteals # lymph;facilitated diffusionmovement along # don concentration gradient;reference to carrier # channel proteins;

monosaccharides or named # amino acids move into epithelial cells;active transportmovement against concentration gradient;

energy # "T re:uired;reference to carrier proteins;

monosaccharides or named # amino acids moved into epithelial cells;reference to codiffusion e.g. glucose and /al;monosaccharides or named # amino acids move into blood;

Describe how sugars are absorbed from the small intestine

into the blood of a mammal.

rinciples=

diffusion into capillaries;

active transport#facilitated diffusion involved;

"T used by active transport;

-etail=

disaccharidases#en@ymes in cell surface membrane;glucose #monomers#monosaccharides actively transported into

epithelial cells;

via protein carriers#channels (in membranes);

facilitated diffusion fromepithelial cell # toards blood;


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&igestion

xplain how the small intestine is adapted to its

function in the absorption of the products of

digestion.

*arge surface area provided by villi # microvilli;

long # folds increase surface area # time for absorption;

thin epithelium;

short diffusion pathay;

capillary netor, absorbs amino acids # sugars;

lacteal for absorption of digested fats;

Maintains a steep concentration gradient

mitochondria supply "T # energy for active transport;

carrier proteins (in membranes);

Describe how carbohydrate eaten as starch is digested to

produce glucose.

0tarch digested to maltose by amylase;

9ound in saliva; 0ecreted by pancreas;

Maltase converts maltose to glucose;

9ound in membranes of cells lining small intestine;

8oth reactions involve hydrolysis;

Describe how maltose in the small intestine is digested"

absorbed and transported to the li&er as glucose.

4ydrolysed by maltase;

Maltase en@ymes in membranes of epithelial cells of small

intestine;

lucose absorption involves diffusion;

"ssociated ith upta,e of sodium ions;


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&igestion

-escribe and explain the roles of diffusion7 facilitated diffusion andactive transport in the absorption of digested food by the ileum.

(allow general points provided correct molecule%particle involved)diffusion

movement along # don concentration gradient;monoglycerides # micelles#fatty acids move into epithelial cells;monoglycerides move from epithelium into blood;chylomicrons move into lacteals # lymph;

facilitated diffusionmovement along # don concentration gradient;

reference to carrier # channel proteins;monosaccharides or named # amino acids move into epithelial cells;active transportmovement against concentration gradient;

energy # "T re:uired;reference to carrier proteins;

monosaccharides or named # amino acids moved into epithelial cells;reference to codiffusion e.g. glucose and /al;monosaccharides or named # amino acids move into blood;

Describe the role of the en!ymes of the digesti&e system

in the complete breakdown of starch.

"mylase;

(0tarch) to maltose=

Maltase;

Maltose to glucose;

4ydrolysis;

(f) glycosidic bond;

Describe and explain how the small intestine is adapted

to increase the rate of absorption

many # pro>ecting villi (J) (no double penalt1 for microvilli);

large surface area (for absorption);

large#good blood supply # many capillaries#blood vessels;

maintains concentration gradients # efficient removal ofdigested products;

thin outer layer # blood vessels near to surface;

short diffusion pathay;

Describe the processes in&ol&ed in the absorption of the products

of starch digestion.

lucose moves in ith sodium (into epithelial cell);

&ia (carrier#channel) protein#symport;

0odium removed (from epithelial cell) by active transport#sodium

potassium pump;


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&igestion

'ow small intestine epithelia are adapted forabsorption

10 Microvilli;20 arge&increased surface area;30 Man* mitochondria;!0 Mitochondria&res'iration 'roduce AT) & release or'rovide energ* for active trans'ort;$0 "arrier 'roteins for active trans'ort;%0 "hannel & carrier 'roteins for facilitated diffusion;(0 "o/trans'ort of sodium ions and glucose or s*m'ort& carrier 'rotein for sodium ions and glucose;+0 Membrane/bound en9*mes digest disaccharides &'roduce glucose


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#ifestyle

and &isease

Describe how atheroma may form and lead to a

myocardial infarction.(6)

1 fatty substance # foam cells # cholesterol in artery all #

under endothelium;2 formation of pla:ues # atherosclerosis # atheroma narros

lumen of artery;

! atheroma creates turbulence # damage to lining of artery;$ (turbulence) increases ris, of blood clot # embolus;% blood clot # thrombus brea,s off;

' (blood clot) lodges in coronary artery;

reduced blood supply to heart muscle;

+ reduced oxygen supply;3 leads to death of heart muscle;

igarette smoking and a diet high in saturated fat increase the

risk of myocardial infarction. xplain how.(6)

arbon monoxide combines ith haemoglobin#causes lessoxygen to be transported;-ecreases concentration of antioxidants in blood;


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#ifestyle

and &isease

Emphsema is another disease of the lungs. "eople withemphsema ma feel wea! and tired. Explain wh.

1 Alveoli brea# do.n & colla'se & ru'ture & .alls thic#en;2 ess surface area & increases diffusion distance & lessdiffusion;3 oss of elastin & elastic tissue & elastase involved;! Alveoli & lungs cannot recoil & s'ring bac# & have reduced

elasticit* & more difficult to e


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#ifestyle

and &isease

Describe how altered D/% may lead to cancer.

1 (-/" altered by) mutation;

2 (mutation) changes base se:uence;

! of gene controlling cell groth # oncogene # that monitors

cell division;

$ of tumour suppressor gene;

% change protein structure # nonfunctional protein # proteinnot formed;

' (tumour suppressor genes) produce proteins that inhibit

cell division;

mitosis;

+ uncontrolled # rapid # abnormal (cell division);

3 malignant tumour;

xplain what is meant by malignant. (,)

(ancer L ) mass of cells that divide continuously #uncontrolled # faster;

(Malignant L ) can spread (to other body parts);

explain what is meant by a malignant tumour and

describe how exposure to cigarette smoke may result in

the formation of a malignant tumour. (6)

(5elative ris, of) lung cancer decreases the longer it is since

giving up smo,ing;(5elative ris, of) lung cancer increases ith the number of

cigarettes smo,ed per day;2

Mass of abnormal cells;


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#ifestyle

and disease

xplain how emphysema reduces the efficiency of gas

exchange in the lungs. %nd suggest two factors that could

increase risk other than smoking

alls of alveoli bro,en don # feer alveoli present;

smaller surface for diffusion;

5reduced elasticity;

ventilation restricted;5

scar tissue formed;less area for gas exchange # sloer gas exchange;

infection eg (chronic) bronchitis;

heredity;industrial pollution must contain reference to

inhalation of particles (dust);

xplain why atheroma may result in cardio&ascular

disease.

ea,en blood vessels may burst # aneurysm;

vessels narro;

blood pressure may rise;

blood clot may occur hich restricts or cuts off blood flo;

in coronary artery this leads to myocardial infarction # heart

attac, # angina;

in artery to brain this leads to stro,e;

Explain hy these factors increase the ris, of developing cardiovascular disease.salt7 smo,ing1at

blood cholesterol level increases;*-*s transport cholesterol in the blood;

*-*s deposit;cholesterol in arteries # atheroma formed;

blood pressure increased;(K)

Salt


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#ifestyle

and disease

xplain how these effects of nicotine increase the risk of

cardio&ascular disease.

noradrenaline produced by 0/0;

stimulates 0"/;

increase in heart rate#cardiac output;

blood pressure increases;

increased ris, of cerebrovascular accident#stro,e;increased ris, of blood clot#thrombosis;

'he diet of a person can increase the riskof coronary heart disease. "(plain how.

10 Too much saturated fat& cholesterol in diet;20 7ncrease in ,& cholesterol in blood;30 Atheroma& fatt* de'osits& 'la>ues in arter* .alls;!0 =educes diameter of & bloc#s coronar* arteries;$0 ess o


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)eart

Describe the parts played by the sinoatrial node (S%/) and the

atrio&entricular node (%2/) in controlling the heart beat.

10"/ initiates # sends heart beat;

2Myogenic # beats spontaneously # does not re:uire nerve impulse;

!5ate of beating influenced by nerves=

$?ave of electrical activity # impulses # excitation passes over

atrium;

%Triggers contraction of atrium;

'Electrical activity can only pass to ventricles # along bundle of

4is by ay of "&/

9ibrous tissue prevents passage elsehere;

+ -elay at "&/;

3 "llos blood to empty into ventricles # atria to empty;

Describe how the regular contraction of the atria and&entricles is initiated and coordinated by the heart itself.

(cardiac) muscle is myogenic;

sinoatrial node#0"/;

ave of depolarisation#impulses#electrical activity (across

atria);

initiates contraction of atria

atrioventricular node#"&/;

bundle of 4is#pur,yne tissue spreads impulse across

ventricles;

ventricles contract after atria#time delay enables ventricles to

fill;

he heart rate of a sleeping person is low. xplain how

ner&es supplying the heart may produce a low heart rate

in a sleeping person.


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)eart

xplain how a rise in blood pressure results in a decrease

in the rate of heartbeat.

1 pressure receptors # baroreceptors # stretch receptors;

2 in aorta # carotid arteries # carotid sinus; (re+ect carotid

bod1)

! send impulses;

(re+ect signals % messages % electronic)$ to cardiovascular centre # medulla # cardioinhibitorycentre;

% send impulses;(once onl1)

' parasympathetic nerves # vagus; (accept inhibitor1 nerve)

to 0"/;

+ release of "h # inhibits 0"/ # decreases impulses from0"/;

3 decreases impulses to "&/ # decreased stimulation of"&/ #

decreases impulses from "&/;*ncreased intensity of e(ercise leads to an

increased heart rate. "(plain how.

10 4uence


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&iseases

xplain the effect of smoking on blood pressure0 (,)

8ecause arteries cannot dilate # dilate less;

4eart must or, harder to force blood through;


38/205

&isease

3hat is atheroma4 (,)

la:ue# fatty material# cholesterol# foam cells# lipoproteinbuild up;


39/205

&iseases

Describe how atheroma is caused and how it may result in

a myocardial infarction. (6)

1. 4igh fat diet#high salt diet#lac, of exercise#age#gender;

7;3 risk factors for one mark

$ot h1pertension as this is given later

2. "theroma forms under endothelium#in artery all;

!. "theroma may narro lumen of artery;

$. "theroma increases blood pressure;%. "theroma promotes clotting;

'. -etails of effect of atheroma on clotting;

. 8lood clot lodges in coronary artery;

+. 5educed blood supply to heart muscle;

?! Reduced o4ygen*glucose supply leading to celldeath"

igarette smoking and a diet high in saturated fat increase the risk ofmyocardial infarction. xplain how.(6)

arbon monoxide combines ith haemoglobin#causes less

oxygen to be transported;

-ecreases concentration of antioxidants in blood;


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%reathing

Describe how muscles in the thorax (chest) cause

air to enter the lungs during breathing.

-iaphragm#intercostal muscles contract;


41/205

%reathing

-escribe ho the medulla in the brain and the stretch

receptors in the lungs maintain the breathing rate hen the

body is at rest.

5espiratory centre in medulla;


42/205

*mmunity

hagocytes and lysosomes are in&ol&ed in

destroying microorganisms. Describe how.

hagocytes engulf pathogens#microorganisms;

Enclosed in a vacuole # vesicle# phagosome;

*ysosomes have en@ymes;

That digest#hydrolyse

molecules#proteins#lipids#microorganism;

%n antigen in a &accine leads to the production of

antibodies. Describe the part played by 7

lymphocytes in this process.(5)

1 macrophages present antigens to 8 lymphocytes;

2 antigen binds to#is complementary to receptors onlymphocyte;

! binds to a specific lymphocyte;

$ lymphocytes become competent#sensitised;

% (8) lymphocytes reproduce by mitosis #(8)

lymphocytes cloned;

' plasma cells secrete antibodies;

Describe how these antibodies are produced in response to

foreign antigens.

antigens attach to macrophages # antigen presenting;

T lymphocytes activated by antigens;

helper T lymphocytes activate;

8 lymphocytes;specific cells (activated);

divide (by mitosis) # clone;

plasma cells # lymphocytes secrete antibodies;

(accept 7 cells% < cells as alternatives throughout)

%ntibodies are protein molecules. xplain why

protein molecules are particularly well suited to

carry out the role of antibodies.

large variety of different molecules;

range of shapes;

tertiary shape;

loc,s onto # complements specific antigen;


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44/205

*mmunity

Describe how 7-lymphocytes respond when antigens

stimulate them.

-ivide by mitosis # form clones;

produce plasma cells;

(plasma cells) ma,e antibodies;

(plasma cells) produce memory cells;

-ivide by mitosis # form clones; produce plasma cells; (plasmacells)

ma,e antibodies;

(plasma cells) produce memory cells;

'mmunisation programmes may use either attenuated ordead microorganisms. Suggest why there might be

problems for the patient when using these &accines .

rocess of ,illing organisms might not be 166O efficient;

live organisms might give rise to fullblon disease;

attenuated organisms are nonvirulent;

but might mutate to virulent forms;

immunity can decline booster in>ections re:uired;

named side effects7 eg allergies;

less effective due to changed antigens;

xplain the role of 7-lymphocytes and -lymphocytes in the

defence of the body against a &irus infection.

8 lymphocytes produce antibodies#involved in humoral response;T lymphocytes involved in cell mediated immunity;

Macrophages present antigens;(specific) 8 lymphocytes recognise#bind to antigen;increase in numbers by mitosis;produce plasma cells (hich ma,e antibodies);

antibodies bind to and clump# agglutinate virus;memory cells produced by 1

stexposure#cloned on 2

ndexposure;

T lymphocytes(helpers) produce lympho,ines#chemicals;hich aid 8 lymphocyte cloning;encourages phagocytes to engulf clumped virus;,iller T cells ,ill virus infected cells;

2accines protect against disease by stimulating theproduction of memory cells. Describe how memory cells

protect the body from disease.

n further exposure to same microorganism;

"ntigen recognised;

9aster response;

reater production of antibodies;


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*mmunity

8i&e two ways in which passi&e immunity differs from

acti&e immunity.

"ntibodies not produced by body;

/o memory cells;

0hortterm # not lifelong;

"ntibodies (or context established) donated by mother #

across placenta # in mil,;

3hat is &accination4ection of antigens#toxoids;

("ntigen from) attenuated microorganism#nonvirulent

microorganisms#deadmicroorganisms#isolated from microorganism;

0timulates the formation of memory cells;

ive two other methods used to prepare vaccines.

,illed microorganism;

modified toxin;

attenuated#heat treated#& treated microorganism;genetically engineered antigens;

isolated antigen;

Describe how the scientists could use 9och:s postulates to show

that the disease is caused by this bacterium.

0ho that bacterium is not present in any animal ithout thedisease;


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*mmunity

xplain why protein molecules are particularly well

suited to carry out the role of antibodies.

large variety of different molecules;

range of shapes;

5

tertiary shape;

loc,s onto # complements specific antigen;

xplain how the respiratory system stops pathogens

getting and the stomach reduces numbers

(a) mucus traps pathogens;

lyso@yme brea,s don bacterial cell alls;

cilia moves pathogens to pharynx;

here they are either salloed or removed;

max. !

(b)

en@yme;

in saliva or gastric >uice;

acid in stomach;

disrupts bacterial membrane # all;

xplain how a host is made less susceptible by the use of

&accination.

nature of vaccine e.g. attenuated strain;

vaccine introduces antigen;

stimulate # sensitise lymphocytes;

memory cells produced;if host meets pathogen (folloing vaccination);

production of same (8#T) lymphocytes;

large number # rapid production of plasma cells # antibodies #

T ,iller cells;

pathogen destroyed before it can affect host;

xplain how the defence mechanisms of the body

reduce the chance of entry by a pathogen.

Epidermis of s,in is dead # ,eratinised so pathogenscannot penetrate;

mucus in respiratory system is trapping stic,y

pathogens;

cilia move fluid # mucus removing pathogens;

tears # saliva # mucus contain lyso@yme brea,ing don

bacterial cell all;

stomach contains hydrochloric acid hich destroys

bacteria;

blood clot prevents entry;

fluid nature of tears ash aay bacteria;

vaginal acid destroys bacteria;

commensal bacteria on s,in compete ith pathogen;

sebum (fatty acid) inhibits bacterial groth;

%&'


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*mmunity

xplain how the body responds both generally and specifically to

pathogens that enter the blood.

action of phagocytes;

ections +ualified e.g. ob>ections to use

of fetal #

animal tissue;

consider lo ris, of disease hen high percentage of

population already

vaccinated#5ef. to A4ead EffectB

xplain how &accination protects against de&eloping a

disease.

T lymphocytes # cells recogni@e antigen in vaccine;

T cells attach to antigens # destroy antigens;

8 lymphocytes # cells clone;roduce lasma ells

produce antibodies (hich ,ill microbe);

memory cells; rapidly produce of these antibodies on re

infection

*any elderly people are &accinated against influen!a.

xplain why it is necessary to &accinate these people

e&ery year.

influen@a virus mutates;

different strains # different shaped antigen;

mutant forms ill not be recognised by lymphocytesmemory cells

immune system; accept elderl1 have weaker immune s1stem


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*mmunity

Suggest how cloning results in the production of 7-

lymphocytes that all ha&e the same antibody-producing

capability

Mitosis;


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*mmunity

%n antigen in a &accine leads to the production of

antibodies. Describe the part played by 7 lymphocytes in

this process.

1 macrophages present antigens to 8 lymphocytes;

2 antigen binds to#is complementary to receptors on

lymphocyte;

! binds to a specific lymphocyte;

$ lymphocytes become competent#sensitised;

% (8) lymphocytes reproduce by mitosis #(8) lymphocytes

cloned;

' plasma cells secrete antibodies;

+hen a pathogen enters the body it maybe destroyed by phagocytosis. &escribehow.

10 )hagoc*te attracted b* a substance& recognisesforeign antigen;20 )athogenengulfed& ingested;30 Enclosed in vacuole& vesicle& 'hagosome;!0 6acuole fuses&joins .ith l*sosome;$0 *sosome contains en9*mes;%0 )athogen digested& molecules h*drol*sed;

hagocytes and lysosomes are involved in destroying

microorganisms. -escribe ho.

hagocytes engulf pathogens#microorganisms;

Enclosed in a vacuole # vesicle# phagosome;

*ysosomes have en@ymes;

That digest#hydrolyse

molecules#proteins#lipids#microorganism;


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Unit #


51/205

3


52/205

3


53/205

3


54/205

Mitosis

Describe the beha&iour of chromosomes during mitosis

and explain how this results in the production of two

genetically identical cells. (


55/205

Mitosis

Describe the role of the spindle in mitosis.

"ttachment of centromeres;

0eparation of (daughter) chromatids;

Mitosis is important in the life of an

organism. ive two reasons why.

10 5ro.th & increase in cell number;20 =e'lace cells & re'air tissue & organs &bod*;30 5eneticall* identical cells;!0 Ase


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Meiosis

Describe what happens to chromosomes in meiosis.(6)

1. hromosomes shorten#thic,en#condense;

2. hromosomes associate in homologous#(described) pairs #

formation of bivalents # tetrads;

!. rossingover # chiasma formation;

$. Poin to spindle (fibres) # moved by spindle;(K)

%. ("t) e:uator#middle of cell;(K)

'. (>oin via) centromere # ,inetochore;(K)

. (4omologous) chromosomes move to opposite poles #

chromosomes separate#move apart; (A""3; Aare pulled

apartB)

+. (airs of) chromatids separated in 2nddivision;

max '

(K) 5 C independent assortmentD

un:ualified L 1 mar,xplain how crossing o&er can contribute to genetic

&ariation.

sections of chromatids exchanged;

sections have different alleles;

ne combinations of (lin,ed) alleles;

*eiosis results in genetic &ariation in the gametes which

leads to &ariation in the offspring formed by sexual

reproduction. Describe how meiosis causes this &ariation

and explain the ad&antage of &ariation to the species.(5)

1. rossingover; ,$3&>any rong ref. to timingN

2.


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Meiosis

Explain the importance of meiosis in the life cycle of a

sexually reproducing organism.

Meiosis halves the number of chromosomes;

5estoration of diploid number at fertilisation;


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Mitosis

ive twoprocesses hich occur during interphase and

hich are necessary for nuclear di&ision to takeplace.

replication of D/%0

% production0

synthesis of proteins=spindle=replication of

centrioles0


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Meiosis

-uring meiosis7 one chromosome from each

homologous pair goes to each of the cellsproduced explain hy

to get haploid#n#half number of chromosomes (in

cells);

so that each cell gets one copy of eachchromosome#gene#full set of genes;

so that fertilisation produces diploid#constantchromosome number;

results in independent assortment;

xplain ho crossing over can contribute to geneticvariation.

sections of chromatids exchanged;

sections have different alleles;

ne combinations of (lin,ed) alleles;

"part from increasing genetic variation7 explain hy

meiosis is important in organisms hichreproduce sexually.

haploid cells produced#halves chromosome number;

fertilisation#fusion of gametes7 diploid number

restored;

chromosome number constant at each generation;


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Benetics*30ugar F phosphate bac,bone gives strength;oiling gives compact shape;0e:uence of bases allos information to be stored;

*ong molecule # coiling stores large amount of information;

omplementary base pairing enables information to be replicated #transcribed;

-ouble helix protects ea, hydrogen bonds # double helix ma,esmolecule stable;Many hydrogen bonds together give molecule stability;

revents code being corrupted;4ydrogen bonding allos chains to split for replication #transcription 5

molecule un@ips easily for replication # transcription.

Explain hy specific base pairing is important in -/"replication.

identical#exact copies made;

same base se:uence as original -/";

both strands act as template#complementary base

pairing

occurs on both strands;


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Aariation

8i&e the meaning and explain one possible cause of each

of the following types of &ariation. ontinuous &ariation

and discontinuous &ariation

5ange beteen extremes#no discrete types;

strong environmental influence;

polygenic#many genes involved;

:uantitative.2

discrete types;

little#no environmental influence#only genetic;

(often alleles of) 1#2 gene;

:ualitative.

3ithin each subspecies there is a range of phenotypes.

xplain the factors that gi&e rise to this &ariation. ()

phenotype depends on genotype and environment;

different local environments can produce variation;

different selection pressures;

mutations producing ne alleles;

meiosis produces ne combinations of alleles#example;

random fusion of gametes # sexual reproduction

Scientists, analsis of blood proteins has indicated alac! of genetic diversit in populations of someorganisms. Describe the processes that lead to areduction in the genetic diversit of populations oforganisms.

10 Mar# for general 'rinci'le of / reduced variet*&number ofdifferent alleles&,-A & reduced gene 'ool in ne.

'o'ulation;20 Counder effect;30 A fe. individuals from a 'o'ulation become isolated&formcolonies:!0 5enetic bottlenec#s;$0 Significant fall in si9e of 'o'ulation%0 Selective breeding & artificial selection;(0 Dsing organisms .ith 'articular

alleles&traits&'henot*'es&characteristics;

ive the meaning and explain onepossible cause of

each of the folloing types of variation

continuous and discontinuous.

(i) range beteen extremes#no

discrete types;

strong environmental influence;

polygenic#many genes involved;

:uantitative. 2

(ii) discrete types;

little#no environmental influence#only

genetic;

(often alleles of) 1#2 gene;

:ualitative.


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%lood

essels

Describe how blood vessels are adapted for theirfunctionAll vessels have endothelium that reduces friction;rterThic#est .all enabling it to carr* blood at high 'ressure &.ithstand'ressure surges;most elastic tissue .hich smoothes out flo. & maintains'ressure;most muscle .hich maintains 'ressure;muscle in .all to control blood flo.;-apillarThin .all allo.ing diffusion&e


63/205

%lood essels

?hen the muscles contract7 the pressure

of the blood in the part of the veinbeteen valves %and 7 changes.

Explain ho this change in

pressure7 together ith the action of

the valves7 helps the blood to floto the heart


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%lood essels

The diameter of a capillary is approximately the

same as the diameter of a red blood cell.Explain one ay in hich this increases

the efficiency of the exchange of

respiratory gases.

lose contact beteen cells and capillary alls;

5educes diffusion path;

or

0los passage of cells through capillary;

More time for diffusion#to reach e:uilibrium;

Explain ho blood capillaries are adapted for theirfunction of gas exchange.

large numbers #netor,7 so large surface area fordiffusion # gas exchange;

thin alls#one cell thic,7 so short diffusion distance;

(not +ust thin or thin membrane)

flattened cells in alls7 so short diffusion distance;

narro lumen7 so red cells touch alls#pass singly;

alls # membranes permeable % porous to gases for

diffusion'

(notAlots of poresB)

(accept low rate of flow' so more time for diffusion%gas

exchange)

(allow * for two features without explanation)

(re+ect fenestrated)

-escribe two ays by hich blood flo in the

veins is maintained.

valves prevent bac,flo;

residual blood pressure from heart;

effect of (s,eletal) muscle contraction

negative pressure from thorax;

Asuction effectB from heart;

ive twoays in hich the structure of a arteryis different from the structure of a vein.

Thic, muscular alls;

reater elastic content;

-o not have valves;

0mall#narro lumen;

54plain the di&erence in thickness between thepulmonar arter (thicker) and the pulmonar

;he thickness of the aorta wall changes all thetime during each cardiac c cle 5 plain h


65/205

%lood

vessels

pulmonary artery (thicker) and the pulmonaryein (thinner)!

igh 'ressure & smoothes out blood flo. & arter* .allcontains more collagen & muscle & elastic fibres &connective tissue;

time during each cardiac cycle! 54plain why!

10 Aorta .all stretches;20 8ecause ventricle&heart contracts & s*stole & 'ressureincreases;30 Aorta .all recoils;!0 8ecause ventricle rela


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Classi-catio

n

Scientists studied two species of orth mericanseahorse. The thought that these two species areclosel related. Describe how comparisons of biologicalmolecules in these two species could be used to find outif the are closel related."om'are ,-A;Se>uence of bases&nucleotides;,-A h*bridisation;Se'arate ,-A strands & brea# h*drogen bonds;Mi< ,-A&strands of different s'ecies;Tem'erature&heat re>uired to se'arate h*brid strandsindicatesrelationshi';"om'are same&named 'rotein;Se>uence of amino acids &'rimar* structure;7mmunological evidence B not a mar#7nject seahorse 'rotein&serum into animal4btain antibodies&serum;Add 'rotein&serum&'lasma from other seahorse s'ecies;

Amount of 'reci'itate indicates relationshi'

"(plain the principles biologists use to classify

organisms into groups compared to older

models.

Consider phylogeny

@ook at eolutionary lineage*history

,ind the point of diergence from a common

ancestor

Consider= genetic= biochemical= embryology=

homology of anatomy

6rganisms are arranged in a hierarchy where large

ta4a (groups) are subdiided into smaller ta4a

(>= 2= C= 6= ,= B=7)0s groups get smaller the similarities between the

species increase

5ach species is gien a binomial name using the

genus and species

6lder models of classi-cation used obserable

features to group organisms

ow does a phlogenic sstem differ to a simple

hierarch$3 mauence is related to ,-A base&tri'letse>uence;

OR

!0 Similar s'ecies have a similar immune res'onse to a'rotein&named 'rotein;$0 More closel* related s'ecies 'roduce more@'reci'itate & antibod*/antigen com'le


68/205

64ygen

dissociation

Describe how haemoglobin is in&ol&ed in absorbing oxygen in

the lungs and transporting it to respiring tissues.

1. diffusion of oxygen into red cell # haemoglobin in red cells;2. high affinity of haemoglobin in high oxygen concentration;

!. (therefore) loads # becomes saturated in lungs # here oxygenabundant;$. oxyhaemoglobin formed;

%. reference to role of haem e.g. energy changes #role of 9e2I

ions # 4b molecule combines ith feer oxygen molecules;'. unloads # lo affinity in lo concentration;

. explanation in terms of dissociation curve i.e. small changesin concentration gives large changes in saturation;+. respiration in tissues gives high 2concentration # high

temperature # high 4I

concentration # lo p43. dissociation curve shifts to right # oxyhaemoglobin dissociationat higher partial pressure

"(plain how o(ygen is loaded, transportedand unloaded in the blood.-/

10 aemoglobin carries o


69/205

64ygen dissociation

During exercise" the rate of respiration of muscle cells

increases. xplain what causes human haemoglobin to

unload more oxygen to these cells.

artial pressure on oxygen in muscle falls more;

high # more carbon dioxide produced;

loers 4;

increase in temperature;

percentage saturation of 4b falls # loers affinity #

increase dissociation;

displaces curve to right # results in 8ohr shift;

Explain ho oxygen in a red blood cell is madeavailable for respiration in active tissues.

*o p4#(more)4I; due to (increased) 2

(increased) respiration;

(ignore refs to buffering action of haemoglobin)

(increased) dissociation of haemoglobin;

*o oxygen tension in tissues#plasma;

xygen diffuses from r.b.c. to tissues;

xplain ho the fetal haemoglobin ma,es it

possible for the fetus to ta,e oxygen fromthe motherBs blood.

9etal haemoglobin has greater affinity for#binds more

readily to oxygen;

at same pp2#concentration of oxygen7 fetal has highersaturation;

correct use of figures from graph (O and pp);

maintains diffusion gradient across placenta.

here is an ad&antage to the shrew in ha&inghaemoglobin with a dissociation cur&e

shifted to the right. xplain this

ad&antage.

(at the tissues at lo pp oxygen) the shreBshaemoglobin is less

saturated ith oxygen # has reduced affinity;

oxyhaemoglobin dissociates more readily #

haemoglobin releases

oxygen more readily # more oxygen released;

alloing greater demand # respiration rate;

The blood leaving a muscle has a loer p4 than the -escribe and explain ho an increase in the rate of


70/205

64ygen dissociation

The blood leaving a muscle has a loer p4 than the

blood entering it. -uring vigorousexercise7 the fall in p4 is even greater.

Explain hat causes this greater fall in

p4.

(in exercise) fasterrespiration rate;

more 2production;

2is acidic # forms carbonic acid;

lactic acid production;

release of 4Iions;

Explain the advantage to the lugorm of having

the dissociation curve to the right giventhat it lives in an area ith lo oxygen

levels.

"ble to be saturated ith oxygen in (very) lo

concentration;

related to lo oxygen concentration inenvironment;

able to unload at only slightly loer

concentration;

-escribe and explain ho an increase in the rate of

respiration in the tissues of a mammalaffects the oxyhaemoglobin dissociation

curve.

(more) carbon dioxide;

decrease in p4#increased acidity#4 ions;

curve moves to the right#depressed;

more oxygen released#4 ions combine ith 4b#4b

reduced;

arbon dioxide helps haemoglobin to

release oxygen to rapidly respiringtissues.

se the graph to explain ho.

-isplaces

dissociation curve to the right#8ohrshift;

*oer affinity for oxygen#less saturated

ith oxygen;

0uggest the advantage to a

d i l f h i h l bi


71/205

64ygen dissociation

ground s:uirrel of having haemoglobin

that has an oxygen dissociation curve to

the left of the curve for humanhaemoglobin.


72/205

;issue ,luid

"(plain how tissue 0uid is formed and how

it may be returned to the circulatory

system.

(4ydrostatic) pressure of blood high at arterial end;

2. 9luid#ater#soluble molecules pass out (re+ect plasma);

!. roteins#large molecules remain;$. This loers the ater potential # ater potential becomesmore negative;

%. ?ater moves bac, into venous end of capillary (re+ect

tissue fluid);

'. 8y osmosis # diffusion;. *ymph system collects any excess tissue fluid;

+. (*ymph) returns to blood # circulatory system # lin, ith

vena cava#

returns tissue fluid to vein;

The tissues of people ho are starving often

sell because of the accumulation oftissue fluid. Explain hat causes this

accumulation of tissue fluid.

0tarvation lin,ed to lo protein content of

diet#*o protein concentration

in plasma#blood;

?ater potential of blood higher#smaller ater

potential gradient;

Tissue fluid formed faster than returned#less

tissue fluid returned to blood;

-escribe the part played by proteins in theplasma in returning tissue fluid to the

capillary.

roduces loer ater potential;

?ater moves into capillary;

8y osmosis#diffusion;

-escribe and explain one ay in hich the

composition of tissue fluid differs from

that of plasma.

contains little#no protein;

molecules too large (to pass through capillary

all);

or

contains less glucose;

some ill have entered tissue cells;

2 max

accept an1 other biologicall1 correct difference

marked in a

similar wa1!

-escribe ho tissue fluid is reabsorbed into 4istamine increases the permeability of


73/205

;issue :uid

-escribe ho tissue fluid is reabsorbed into

blood capillaries.

eneral principle=

blood exerts an Cosmotic forceD hich causesfluid to move bac,

into capillaries;

-etail=

caused by plasma proteins (retained in blood);

ater moves into blood by osmosis# diffusion;

small soluble molecules move into blood by

diffusion;

Explain the lin, beteen insufficient protein in

the diet and the accumulation of tissue

fluid.

*ess protein in blood # plasma # capillary;

?ater potential of blood increases;

*ess reabsorption occurs # lymph system cannotdrain excess.

4istamine increases the permeability of

capillary alls so that large molecules canpass through. Explain ho this change in

permeability results in selling round thebite.

roteins can move into tissue fluid;

*oers ater potential of tissue fluid;


74/205

'issue 0uid

gg p g

blood pressure and theaccumulation of tissue fluid.

4igh blood pressure increases rate of filtration #

forces more fluid out;

*ymph system cannot cope # higher pressure

reduces reabsorption;

3escribe how tissue :uid is formed and how it is

returned to the circulatory system!

Cormation10 igh blood & h*drostatic 'ressure & 'ressure filtration;20 Corces .ater & fluid out;30 arge 'roteins remain in ca'illar*;

=eturn!0 o.er .ater 'otential in ca'illar* & blood;$0 ,ue to 'lasma 'roteins;%0 Water enters ca'illar* & blood;

(0 8* osmosis;+0 "orrect reference to l*m'h;

p

ater is exchanged beteen the blood andtissue fluid as blood flos along the

capillary.

4 forces ater out;

idea that 4 is ChigherD than ?;

proteins remain in blood (increases ?);idea that ? is no ChigherD than 4;

ater returns by osmosis # along ?

gradient;

ater moves out at arteriole end and bac,in (at venule end);


75/205

Bas

e4change

his insect has more than >.5 million tracheoles. he

distance between the ends of the tracheoles in the muscle

is approximately pm. xplain how these features allow

efficient oxygen supply.

@arge number gies large (total) surface area"

,or di&usion"

7hort distance between tracheoles gies shortpathway"

Moement*di&usion through muscle is slow"

Reject references to muscle simply being close

to tracheoles. Must convey

idea of short pathway to gain credit for third

point.

% thin surface and a diffusion gradient are both featuresof gas exchange surfaces. Describe how these are achie&ed

at the gas exchange surfaces of a mammal0

(8all of) aleoli * capillaries hae single epithelial

layer*

single layer of cells*

aleoli and capillaries close together"

epithelium :attened*paement epithelium"

entilation maintains high 6#*low C6#

concentration(in aleoli)"

blood :ow*circulation maintains high C6#*

low 6#concentration(in blood)"

xplain how the features of the al&eoli maximise

absorption of oxygen into the blood.

@arge surface area"

:attened cells * suamous epithelium * single

layer of epithelial cells"

short di&usion pathway"

role of surfactant"

e4tensie blood supply maintains a high di&usion

gradient"

narrow capillaries slows blood :ow D more time

for di&usion"

xplain how the gills of a fish are adapted to form aspecialised exchange surface.

0tructure of filaments;

large number of lamellae;

9lattened epithelial cells;0hort distance beteen ater and blood # short diffusion

pathay # maximum diffusion gradient;

ountercurrent mechanism # description;

maintains diffusion gradient along length # prevents oxygenconcentrations reaching e:uilibrium;

Role of entilation mechanism in producing water

:ow oer gills"

Circulation replacing blood"


76/205

Bas

e4change

&escribe the counter current principle of

gas e(change in 1sh

counter current* blood :ow in opposite direction

to water :ow"

giing ma4imum distance for o4ygen to :ow

in*carbon dio4ide out*gas e4change"

description of how a counter current works"

gill lamellae gie a large surface area"

thin surface of lamellae*short distance between

surface of lamellae and blood capillaries"

lamellae held edge on to water :ow"

:ow of water across gills in one direction"

entilation system to maintain the water :ow"

blood circulation to maintain the blood :ow"

n insect lives in air. Describe how the insect isable to obtain oxgen and limit water loss.

1 Air enters through o'en s'iracles;2 Through tracheae;3 ,iffusion gradient in trachea! Tracheae associated .ith all cells&closel* associated.ith cells;$ 4


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Bas

e4change

mammalian breathing system enables efficient uptake of

oxygen into the blood.(6)

1. alveoli provide a large surface area;

2. alls of alveoli thin to provide a short diffusion pathay;

!. alls of capillary thin#close to alveoli provides a short diffusion pathay;

$. alls (of capillaries#alveoli) have flattened cells;

%. cell membrane permeable to gases;

'. many blood capillaries provide a large surface area;. intercostal#chest muscles#diaphragm muscles # to ventilate

lungs # maintain a diffusion#concentration gradient;

+. ide trachea # branching of bronchi#bronchioles for

efficient flo of air;3. cartilage rings ,eep airays open;

-escribe ho a large difference in oxygen

concentration is maintained beteen a fish gill and thesurrounding ater.

9ish has ventilation system hich replaces ater;

highly oxygenated ater

(circulatory system brings in) blood ith lo

concentration of

oxygen#blood removes oxygen;

counter current system#description;

surfaces. -escribe ho these are achieved at the gas exchange surfaces of

a mammal and leaf

(all of)alveoli # capillaries have single epithelial layer#

single layer of cells#

alveoli and capillaries close together;

epithelium flattened#pavement epithelium;

ventilation maintains high 2#lo 2concentration(in alveoli);

blood flo#circulation maintains high 2#

lo 2concentration(in blood);

max. !

(ii) leaf very thin # only a fe cells thic,;

intercellular spaces exposes cell surface membrane#

all directly to gases;

production of 2in photosynthesis maintains high oxygen concentration;

use of 2in photosynthesis maintains

lo carbon dioxide concentration;-escribe the adaptations of a mammalian lung hich

ensure a short diffusion pathay for respiratory gases.

ne cell thic,#single layer of(epithelial) cells lining

alveolus;

flattened#pavement#s:uamous;

capillaries surrounded by single layer of cells;

capillaries and alveoli are close;


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as

e(change

This insect has more than 1.% million tracheoles. The

distance beteen the ends of the tracheoles in the

muscle is approximately $ pm. Explain ho these

features allo efficient oxygen supply.

*arge number gives large (total) surface area;

9or diffusion;

0hort distance beteen tracheoles gives short pathay;

Movement#diffusion through muscle is slo;

acent cells # alls not touching.

uggest tworeasons hy it ould be very difficult toextract sufficient oxygen from ater by moving ater

in and out of lungs.

?ater too dense to move in and out of lungs;

lo oxygen concentration in ater;

high metabolic rate in mammals re:uires high oxygen

inta,e.

Explain ho the countercurrent principle helps fish to

extract oxygen from ater.

Explain ho the ventilation mechanism of a fish and

the structure of its gills result in the efficient upta,e of

oxygen from ater


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as

e(change

?ater flos in opposite direction to blood;

across (gill) lamellae;

so difference in concentration maintained;

diffusion gradient maintained # diffusion over full

length.

-escribe and explain ho fish maintain a flo ofater over their gills.

1. mouth opens7 operculum#opercular valve shuts;

2. floor of mouth loered;

!. ater enters due to decreased pressure # increased

volume;

$. mouth closes7 operculum#opercular valve opens;

%. floor raised results in increased pressure # decreasedvolume;

'. high#increased pressure forces#pushes ater overgills;

oxygen from ater.

-escribe and explain ho the structure of the mammalianbreathing system enables efficient upta,e of oxygen into the blood.

1. alveoli provide a large surface area;

2. alls of alveoli thin to provide a short diffusion pathay;

!. alls of capillary thin#close to alveoli provides

a short diffusion pathay;

$. alls (of capillaries#alveoli) have flattened cells;

%. cell membrane permeable to gases;

'. many blood capillaries provide a large surface area;

. intercostal#chest muscles#diaphragm muscles # to ventilatelungs #

maintain a diffusion#concentration gradient;

+. ide trachea # branching of bronchi#bronchioles for efficient

flo of air;

3. cartilage rings ,eep airays open;

-escribe ho the gills of a fish are ventilated after

ater has entered through its mouth.

"n insect lives in air. -escribe ho the insect is able to

obtain oxygen and limit ater loss.


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as e(change

g

fish closes mouth and raises the floor of the mouth;this decreases the volume # increases the pressure (of

mouth);


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as e(change

p p

flo of ater and of blood shon in the micrographis useful to a fish.

Maintains concentration gradient (over hole length

of gill) # diffusion can

occur over hole gill;

More oxygen enters blood (# more 2leaves);

More (aerobic) respiration # more energy release in

muscle # for simming;

more needed 3$> onl1

0ir moes into the lungs during inspiration!54plain how the diaphragm causes this!

10 ,ia'hragm contracts&moves do.n& flattens;20 7ncreases volume of thora


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0ntibiotics

"(plain how resistance to an antibiotic could

become widespread in a bacterial population

following a gene mutation conferring resistance

in just one bacterium.

1! freuent use of antibiotic creates selection

pressure* antibiotic kills bacteria"

#! bacteria with natural mutation* resistance hae

(selectie) adantage oer others * described"

$! (surie to) reproduce more than other types"

! pass on adantageous allele* mutated allele in

greater numbers"

+! freuency of (adantageous) allele increases in

subseuent generations"

(penalise use of gene! instead of allele once only"

.! freuency of resistant types increases in

subseuent generations"

ive two other ays in hich antibiotics canprevent bacterial groth.

disrupts cell all#prevents cell all synthesis;

stops -/" replication;

Describe one other wa in which antibiotics can act againstbacteria. Explain wh this mode of action is effective againstthe bacteria.)revent ,-A re'lication & 'revent m/=-A s*nthesis & 'reventtransfer of amino acids to ribosomes & re'roduction & transcri'tion &translation & 'rotein s*nthesis;

1

)reventing ,-A re'lication: bacterial cell .ill be unable to divide;

)revent re'roduction 2nd

'oint onl*; 'o'ulation of bacteria .ill not

increase;/0

)reventing m/=-A s*nthesis & no m/=-A means code not 'assed

to

transcri'tion; ribosomes;no 'rotein s*nthesis & no ne. en9*mes;

/0

)reventing transfer of amino acid no 'roteins made;

to ribosomes & translation no en9*mes & no 'roteins structures;

'revent 'rotein s*nthesis 2nd

'oint onl*;

3escribe how gene transmission and selectionhae increased the diEculty of treating bacterialinfections with antibiotics!

10 Antibiotic resistant gene&allele;20 6ertical gene transmission;30 =esistant bacteria survive and re'roduce &'o'ulation of resistant bacteria increases;!0 7ncrease in fre>uenc* of resistant allele&gene infuture generations;$0 ori9ontal gene transmission;0 )lasmid;(0 "onjugation & 'ilus tube;+0 ori9ontal transmission& conjugation can occurbet.een bacteria of different s'ecies;

Describe the structure of a cellulose molecule and explain

&escribe how the structure of (ylem is


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7tructures

and function

Describe the structure of a cellulose molecule and explain

how cellulose is adapted for its function in cells.

Made from FDglucose"#! Goined by condensation*remoing molecule ofwater*glycosidic bond"$! 1H link speci-ed or described"! I,lipping oerJ of alternate molecules"+! 'ydrogen bonds linking chains*long straight

chains".! Cellulose makes cell walls strong*cellulose-bres are strong"/! Can resist turgor pressure*osmoticpressure*pulling forces"! %ond diEcult to break"?! resists digestion*action ofmicroorganisms*enzymes"

Palisade cells are the main site ofphotosynthesis. "(plain one way in which a

palisade cell is adapted for photosynthesis.

idea ofmany chloroplasts * lots of chlorophyll"

to trap or absorb light (energy)"

elongated cells with long a4is perpendicular to the

surface"

idea o#ight has a longer pathway allowing ma4imum

light absorption * light penetration"

chloroplasts moe"

to trap or absorb light (energy)"

range of pigments"can absorb a range of waelengths * colours * for ma4

light absorption"

large 7!0! or cell wall feature e!g! thin * permeable"

for (rapid) C6#absorption"

&escribe how the structure of (ylem is

related to its function.

Aessels"

'ae no end walls * hollow * no cytoplasm"

0llows unrestricted :ow of water!

@igni-cation"

2roides support * strength * impermeability"

2its allow lateral transport"

;racheids with porous end walls!

"(plain how the properties of starch arerelated to its role in living organisms -2/

role storage;plus

properties insoluble;

explanation therefore stays inside cell#membrane;

orproperties large molecule#coiled#branched;

explanation lots of glucose#carbohydrate molecules in small

space#stays inside cell;

or

properties osmotically inactive;explanation does not cause the cell to absorb ater;

Explain ho cellulose gives cotton its strength. 'wo ways in which the structure of cellulose is


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Structures for

function

(long) straight#unbranched chains;

(idea of more than 1) chains lie side by side #

form (micro)fibrils;

idea of 4 bonds holding chains together;

"(plain one way in which the structure of

cellulose is linked to its function.

10 /bonds & micro&macro fibrils &fibres;

20 Strength & rigidit* & inelasticit*;

di&erentfrom the structure of starch!

starch10 1! and 1% bonds&contains 1% bonds &branching20 All glucoses& monomers same .a* u'30 eli


85/205

2lant

transport

of a tree to the lea&es


86/205

2lant

transport

7n da*light most of the .ater eva'orates from the leaves butsome is used b* the 'lant0,escribe the .a*s in .hich this .ater could be used b* the'lant0 %.hich is in a continuous column & .ater molecules cohere;cohesion due to bonding;column doesnt brea# because of adhesion .ith


87/205

2lant

transport

stem blocks the mo&ement of water through that &essel.

Bse the cohesion-tension theory to explain why.

Evaporation from leaves # transpiration;

?ater in xylem under tensionK#negative pressure#pulled up;

?ater molecules cohereK#stic, together#form hydrogen

bonds;,gnore: references to adhesionN

0o ater a single column;"ir bubble brea,s column # prevents cohesion;

3se our !nowledge of the cohesion4tension theor of

water movement through a plant5 to explain wh thediameter of the trun! is smallest at midda.10 ,iameter of trun# minimal at .armest & brightest time of da*&midda* F .armest & brightest;20 Stomata o'en in light more .ater loss;30 Water eva'orates more .hen .arm & more heat energ* for.ater eva'oration;!0 *drogen/bonding bet.een .ater molecules;$0 "ohesion & described bet.een .ater molecules;%0 Adhesion described bet.een .ater molecules and .alls of


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2lant transport

"poplastic F &ia cell alls # spaces external to cell membrane # external to

cytoplasm # beteen cells;

"s far as endodermis # asparian strip # layer of ax;

aused by transpiration pull;

ohesion # hydrogenbonding beteen ater molecules;

0ymplastic F Through cell surface membrane (of epidermis # root hair cell) #

ref.vacuoles membrane;

4igh to lo # s;

-iffusion # osmosis;

elltocell via plasmodesmata # via strands of cytoplasm;

0ecretion # active transport of ions into xylem by endodermis;

5

"ctive upta,e of ions from soil at epidemis;

*oers # sin xylem # increases osmosis into xylem;Explain ho root pressure and cohesionFtension are responsible for the

movement of ater in xylem vessels.

5oot pressure=

1. "ctive transport of salts into xylem;

2. Endodermis # asparian strip;

!.revents lea,age # ater # ions must use symplast pathay;

$. *oer ater potential inside xylem;

%. ?ater (enters xylem) don ? gradient # by osmosis;

'. pard ater movement by root pressure is relatively lo;

$ max

ohesion tension=

. Transpiration # evaporation of ater;

+. 9rom spongy mesophyll # through stomata;

3. *oers ater potential of mesophyll;

16. ?ater molecules hydrogen bond # stic, together;11. 5ef. to columns # chains;

12. ?ater pulled up xylem (creating tension);

1!. "dhesion beteen ater molecules and xylem vessel alls;

1$. 5esponsible for ma>ority of ater movement up xylem vessels;

is smallest at midday.

1. -iameter of trun, minimal at armest # brightest time of day #

midday L armest # brightest;

2. 0tomata open in light more ater loss;

!. ?ater evaporates more hen arm # more heat energy for ater

evaporation;

$. 4ydrogenbonding beteen ater molecules;

%. ohesion (# described) beteen ater molecules;

'. "dhesion (described) beteen ater molecules and alls of

xylem vessels;

. (Jylem) pulled inards by faster flo of ater # pulled in by

tension;

+. 5educed pressure at leaves # top of plant # pull from top # from

leaves #

tension from leaves # from top of plant due to transpiration #

evaporation;

3. ?ater pulled up plant;Explain ho the negative pressure in the xylem

vessels of the leaves causes ater to move

up the plant from the xylem in the roots.

1. continuous # leaf to rootcolumn of ater;

2. 4bonds;

!. cohesion;

$. column under tension # pull

transmitted;

-escribe onepiece of evidence that supports the

root pressure theory and explain ho it

supports this theory.

The diameter of a tree is less during the day7 hen the tree is

transpiring7 than it is at night. Explain ho this supports

cohesion but not root pressure


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2lant transport

0uitable accepted evidence7 1 mar, for evidence and 1

mar, for explanation F

E


90/205

2lant transport

an increase in air temperature anddecrease in ater content of soil

(i) 4igher temperatureprovides more ,inetic energy;

9or evaporation # diffusion;

"ir can hold more ater vapour # increases

ater potential gradient;2 max

(ii) 5educestranspiration as less ater upta,e;

5eference to ater potential gradient (leaf

and air # soil and root);

-escribe and explain ho ater in the

mesophyll cells passes out of theleaf.

(pathay from cells) along cell alls #

through spaces and out through stoma(ta);

by diffusion (disualif1 if osmosis

mentioned);

don a ?#diffusion#concentrationgradient;

according to the cohesion tensionhypothesis.

1. ater evaporates#transpires from leaves;

2. reduces ater potential in cell #aterpotential#osmotic gradient across

cells (ignore reference to air space);

!. ater is dran out of xylem;

$. creates tension (accept negative pressure not

reduced pressure);

%. cohesive forces beteen ater molecules;

'. ater pulled up as a column;

se your ,noledge of the cohesiontension

theory to explain ho ater in the xylemin the roots moves up the stem

ater evaporates#transpires;

reduces ater potential # creates ater potential

gradient # increases

osmotic gradient #

moves via apoplast pathay;

ater dran out of xylem;

creates tension#pulling effect # creates negative

pressure (in context)'

cohesive forces or 4 bonding beteen ater

molecules # ater moves

as a column;

-escribe two features you ould expect in the leaves of a tree

adapted to a dry environment. Explain ho each feature helps

xplain how the presence of Chairs and rolled lea&es

reduce water loss in xerophytic plants. ()


91/205

Kerophytic

adaptations

adapted to a dry environment. Explain ho each feature helpsthe treeBs survival. (')

0un,en stomata;

ater evaporation into pit creates local humidity;

increased humidity reduces gradient for ater evaporation;

close arrangement of stomata;

diffusion shells of individual stomata overlap;

interferes ith ater diffusion and slos evaporation;

restriction of stomata to loer side of leaf;

rate of air movement belo leaf less# heating effect of sun

less;

gradient for ater evaporation reduced# ater molecules have

less

,inetic energy;

continued

thick cuticle*wa4*suberin (on upper surface)"(wa4*suberin )waterproof"

water unable to di&use onto surface to

eaporate=

presence of trichomes* hairs"

surface traps water close to leaf surface"

increased humidity reduces gradient for water

eaporation"

reduced leaes*spines*small surface area to

olume"

less surface area for eaporation"more distance across leaf for water to di&use"

rolled leaves;

stomata enclosed in localised humidity;

increased humidity reduces gradient for ater evaporation;

reduce water loss in xerophytic plants. ()

Trap moist air # increase humidity;

5educe air flo (around leaf surface # stomata);

*oer ? # ater vapour concentration gradient (beteen

inside

and outside of leaf);

0hield stomata from high temperature # high light

intensity # ind; ignore sun

5educe transpiration # evaporation # diffusion of ater(vapour);

-escribe and explain ho three structural features reduce the rate

of transpiration in xerophytic plants75olled leaves Freduces ater potential gradient air movement across stomata #traps air

hich becomes saturated # moist # humid # reduces surface area;0un,en stomata F

reduces ater potential gradient air movement across stomata #traps airhich becomes saturated # moist # humid;Thic, cuticle F

5educes cuticular transpiration # reduces ration greater diffusiondistance;

4airs

traps air hich becomes saturated # moist # humid;5educed leaves # spines Fless surface area # feer stomata (for evaporation).

3ater &apour diffuses through open stomata into the

atmosphere. Describe two structural adaptations of the lea&am

Documents

Long Answer Questions A LEVEL BIOLOGY