Biology U2.doc

7/26/2019 Biology U2.doc

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Biology Unit 2: (Development, Plants and the Environment)

2.3.1 Describe the ultrastructure of a typical eukaryotic cell (nucleus, ribosomes, rough and

smooth endoplasmic reticulum, mitochondria, centrioles, lysosomes, nucleolus)

2.3.2 Distinguish between the ultrastructures of prokaryotic and eukaryotic cells

The main differences beteen the e!"aryotic and pro"aryotic cells are:

The pro"aryotic cell has chloroplasts

The pro"aryotic cell has a central vac!ole

The pro"aryotic cell has a cell all

The pro"aryotic cell has plasmodesmata

The e!"aryotic cell has membrane bo!nd organelles

2.3.3 Eplain the role of the rough endoplasmic reticulum and the golgi apparatus in protein

trafficking within cells

The ro!gh endoplasmic retic!l!m is responsible for transporting proteins made by ribosomes to

other parts of the cell# $fter the protein has passed thro!gh the ro!gh endoplasmic retic!l!m, they

are sent to the golgi apparat!s# $s they move thro!gh the golgi apparat!s, they are modified andpac"ed into vesicles#

2.3.! Eplain the role of D"# replication and mitosis in the cell cycle

$nterphase% ne cell organelles are synthesised and D%$ replication occ!rs# There m!st be eno!gh

information here in order to prod!ce to ne cells#

&rophase%the chromosomes condense (shorter and thic"er) and become "non as to strands

chromatids, the to visible strands are attached at one region "non as the centromere#

&icrot!b!les from the cytoplasm form a three dimensional str!ct!re called the spindle#

'etaphase' The n!clear envelope is bro"en don and the start of metaphase begins# The

chromosomes centromeres attach to the spindle fibres at the e!ator##naphase' The centromeres split, and the spindle fibres shorten, p!lling the to halves of each

centromere in opposite directions (one chromatid to each pole)


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elophase%The chromosomes !nravel and the n!clear envelope reforms, so that the to sets of

genetic information become enclosed in seperate n!clei#

ytoplasmic di*ision% The cell s!rface membrane constricts aro!nd the centre of the cell, hich

narros !ntil the cell is cleaved into to ne cells# $ ring of protein filaments bo!nd to the inside

s!rface of the cell s!rface membrane are said to contract in this process#

2.3.+ Eplain the significance of mitosis for growth and aseual production

&itosis occ!rs in any organism as it develops from a single cell into a m!lticell!lar orgasnism# t

ens!res that a m!lticell!lar organism has genetic stability, and allos old and damaged cells to be

replaced ith identical ne copies#

*ome organisms reprod!ce itho!t prod!cing gametes, they gro copies of themselves by mitosis,

prod!cing offspring hich are genetically indentical to themselves# This is !sef!l for the orgasnisms

s!rvival#

2.3. Eplain how mammalian gametes are specialised for their functions including the

acrosome reaction

The cytoplasm in the ov!m contains protein and lipid food reserves for the early development of the

embryo# The ov!m is a large cell incapable of independent movement#

The sperm is m!ch smaller than the ov!m, and can move# The sperm has a long tail poered by

energy released by the mitochondria hich enables it to sim# n order to penetrate the ov!m, the

acrosome in the head of the sperm releases digestive en+ymes hich brea" don the elly li"e

coating of the ov!m#

2.3.- Eplain the importance of fertilisation in seual reproduction

-ertilsation is the process here the n!cle!s from the sperm cell enters the ov!m, and the genetic

information of both gametes f!se, forming a fertilised ov!m called a +ygote# *e.!al reprod!ction is

important beca!se it allos the +ygote to have genetic information from both parents#


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2.3. Eplain how meiosis results in the hal*ing of chromosomes numbers and the

introduction of *ariation through random assortment

The process of meiosis:

/ell prepares for meiosis !st ho it does for mitosis#

There are identical chromosomes pairs# Each chromosome then d!plicates itself#

The homologo!s chromosomes line !p on the e!ator of the cell and then separate#

*ister chromatids separate and gametes are formed, each ith half the n!mber of original

chromosomes#

D!ring the process of meiosis, only one chromosome from each homologo!s pair ends !p in each

gamete, hich is a random process# This is "non as random assortment# -!rthermore, beca!se the

gametes oin ith another gamete at fertilsation this pretty m!ch ens!res variation#

2.3./ Eplain what is meant by stem cells, pluripotency and totipotency

Totipotent is a ord !sed to describe a cell hich can develop into any type of cell# Pl!ripotent is a

cell hich can only develop into many types of cells b!t not all, for e.ample, embryonic stem cells#

These cells are !nspecialised#

$s the embryo develops, the cells of hich it is made from become increasingly differentiated, that

is they become specialised#0oever, even in ad!lts, some cells retain the ability to give rise to a

variety of different cell types, hich are "non as m!ltipotent stem cells (blood stem cells in bone

marro can develop into red blood cells etc#)

2.3.10 Discuss the moral, ethical and and sprititual implications of stem cell research

1!st abo!t everyone agrees that there are no ethical obections to !sing m!ltipotent stem cells

derived from ad!lts# 0oever, most scientist belive that these stem cells are li"ely to be of less

val!e than the pl!ripotent cells available from an embryo# *ome people believe that the embyro

sho!ld be granteded f!ll h!man stat!s from the moment of its creation# B!t some people say that as

the embryo develops, it increases in its ability to become a h!man being, and so early stages of

research can be eighed !p against the potential benefits of the research#

2.3.11 Eplain how genes can be switched on and off by D"# transcription factors and how

this gene switching gi*es rise to specialised cells

$s the embryo develops, cells differentiate and become specialised for one f!nction# The f!nction

of each cell type is dependent on the proteins that it synthesises# This is determined by hich genes

in a cell are e.pressed (that is, the ones hich are transcribed and translated to prod!ce the proteins

they code for)# *o hat is it that sitches on the genes appropriate for a cells specialised f!nction3

4enes are sitched on by s!ccesf!l formation and attachment of the transcription initiation

comple. on the promoter region of the D%$# 4enes remained sitched off by fail!re of the

transcription initiation comple. to form and attach to the promoter region, hich can be d!e to the

absence of protein transcription factors or the action of repressor molec!les#

The technical term for sitching on of a gene is called ind!ction#


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2.3.12 Eplain how certain characteristics may be affected by both genotype and the

en*ironment, including human height, skin colour, hair colour and cancers

/haracteristics in an orgasnism, s!ch as height, se., blood gro!p are "non as phenotypes# These

phenotypes can either be controlled by genotypes (the genetic ma"e !p) or the environment in

hich an individ!al develops#

0!man height is controlled by genetics b!t there are clearly some environmental factors involved,

for e.ample, taller man are said to have more children, hich o!ld res!lt in grad!al change in the

genetic ma"e !p of the pop!lation# -!rthermore, better n!trition has leaded to increased groth#

*"in and hair colo!r are also an e.ample of ho the environment and o!r genotypes interact ith

each other# 5!r s"in and hair colo!r is genetic, b!t for e.ample, o!r s"in prod!ces 6itamin D hen

e.posed to the *!n hich ma"es melanin and so ma"es o!r s"in dar"er#

2.3.13 Eplain that cancers arise from uncontrolled cell di*ision, and describe genetic,

en*ironmental and lifestyle causes of cancer

/ancer occ!rs hen the rate of cell m!ltiplication is greater than the rate of cell death# This ca!ses

the groth of at t!mo!r, often in tiss!es ith high rate of mitosis# f there is m!tations in the genes,

it can stop t!mo!r s!ppressor genes from brea"ing the cell cycle, so the cell cycle contin!es#

/ancer occ!rs by damage to D%$# D%$ can be damaged by lifestyle factors s!ch as increased

e.pos!re to U6 light or diet# $ diet ith plenty of fresh fr!it and vegetables provides antio.idants

hich destroy radicals (radicals contrib!te to D%$ damage)# t can also be damaged by chemicals,

s!ch as carcinogens, hich may be in the environment# $lso, it can be ca!sed by genetics factors,

here D%$ is copied incorrectly in gamete formation, so an inherited form of cancer can form#

2.3.1! Discuss the principle outcomes of the uman enome &roect and the social, moral and

ethical issues which arise from it

$ genome is all the D%$ of an organism incl!ding the genes that carry o!t all the information for

ma"ing the variety of proteins re!ired by the organism# The h!man genome proect aims to

identify the tho!sands of genes in the h!man body, and to determine the se!ence of bases that

ma"e !p D%$#

t has prod!ced these o!tcomes:

Detailed information abo!t the genome

dentification of ne genes (breast cancer gene, colo!r blindness gene) ndentification of ne dr!g targets

Preventative medicine and improved dr!g treatment (side effects for patients may be

different hen !sing the same dr!g, believed to be a slight alteration in the genome for each

person, so the h!man genome proect aims to pinpoint these differences)

nvestigating evol!tion of the h!man genome (compares o!r genome ith other animals, it

is possible to loo" at the evol!tion aspect of o!r genetics)

0oever, there are iss!es relating to the 0!man 4enome Proect:

7ho ons and controls genetic information3

0o does personal genetic information affect the individ!al and societies perceptions of the

individ!al3 Do peoples genes ma"e them behave a certain ay3

7here is the line beteen medical treatment and enhancement3


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2.!.1 4ecall the typical structure of a plant cell (presence of cell wall), chloroplasts,

amyloplasts, *acuole, tonoplast, plasmodesmata, pits and middle lamellae

2.!.2 ompare the structure and function of the polysaccharides starch and cellulose

including the role of hydrogen bonds between beta glucose molecules in the formulation of

cellulose microfibrils

7oods strength comes from the thin cell!lose alls of plant cells and the gl!e that holds them

together# /ell!lose is a polysaccharide, b!t the gl!cose hich it is made from is slightly different

from that hich forms starch# *tarch is made from alpha gl!cose, hereas cell!lose is made from

beta gl!cose# /ell!lose have glycosidic bonds hich are 8,9, !nli"e starch, there are no 8,

glycosidic bonds# t is this hich ma"es cell!lose a long !nbranched molec!le#

5n cell!lose, hydrogen bonds form beteen the '50 gro!ps in neighbo!ring cell!lose chains,

forming b!ndles called microfibrils# ndivid!ally, the hydrogen bonds are relatively ea" compared

ith the glycosidic bonds, b!t together the large n!mber of hydrogen bonds in the microfibril

prod!ce a strong str!ct!re#The gl!e hich holds the cell!lose microfibrils together is "non as

hemicell!lose, and the arrangement of the microfibrils ithin a matri. of hemicell!lose ma"es the

cell all very strong#


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2.!.3 Describe the structure of sclerenchyma fibres and ylem *essels and where they are

found in the plant stem. Describe how their physical properties enable them to be used for

human benefit

To b!ild a tall plant s!ch as a tree, some of the cells ithin the stem m!st be stiffened to provide

mechanical s!pport, and they also m!st allo ater and minerals to pass from the roots to the

leaves# There are to specialised types of cells hich allo this f!nction to be carried o!t: ;ylem vessels < these form t!bes for transport, and their stiffened cell alls help s!pport

the plant

*clerenchyma fibres < col!mns of these cells ith their stiffened cell alls also provide

s!pport

The .ylem and the sclerenchyma fibres are fo!nd in the stem# These fibres are !sef!l for h!mands

beca!se they are long, thing, fle.ible and strong# They can be !sed to ma"e clothes, paper, and rope#

They can also be a s!stainable reso!rce beca!se they can be added to other materials to ma"e

biocomposites#

2.!.!Eplain the relationship between structure and function in sclerenchyma fibres(support) and in ylem *essels (support and transport of water and mineral ions through the

stem)

2.!.+ Eplain the importance of water and inorganic ions (nitrate, calcium and magnesium) to

plants

2.!. Eplain the role of adhesion, cohesion, and the transpiration steam in the mo*ement of

water through the stem

;ylem vessels for transport:

;ylem vessels are long thin lignified (aterproof) col!mns hich are contin!o!s from the roots to

the leaves# The ater tranports thro!gh the .ylem vessels as follos:

8# 7ater vapo!r diff!ses o!t thro!gh the stoma don a diff!sion gradient

2# 7ater evaporates from the s!rface on cells lining the s!bstomatal cavity

=# 7ater moves across the leaf don a diff!sion gradient

9# 7ater leaving the .ylem red!ces hydrostatic press!re

># 7ater moves !p the .ylem vessel d!e to the difference in hydrostatic press!re (lo at the

top, high at the bottom)

The contin!o!s col!mn of ater moving !p the .ylem vessel is "non as the transpiration steam#

To forces help to hold this col!mn of ater together, adhesion and cohesion# $dhesion in the

vessels occ!rs hen ater adheres to the alls of the vessels, helping to hold the col!mn of ater

ithin the vessel# Beca!se of the large s!rface area to vol!me ratio (d!e to narro diameter of thevessels), hich creates high adhesive forces# /ohesion occ!rs beca!se there is strong cohesive

forces beteen ater molec!les, hich "eeps the ater together as a contin!o!s col!mn#

The rate of transpiration is greater hen there are dry arm conditions beca!se this increases

evaporation from the leaf#

The .ylem vessels also help to transport inorganic ions# These are re!ired thro!gho!t the plant,

beca!se the nitrates are !sed in every cell to man!fact!re proteins, $TP etc# f the inorganic ions are

not absorbed in s!fficient amo!nts, then the plant ill sho deficiency symptoms#

;ylem vessels and sclerenchyma fibres for s!pport:?ignin not only aterproofs the cell all, b!t ma"es it m!ch stiffer and gives the plant great tensile

strength, and this is the case for both .ylem vessels and sclerenchyma fibres#


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2.!.- ompare how 5illiam 5ithering de*eloped his digitalis soup with drug de*eloping and

testing nowadays

7illiam 7ithering had a friend ho as shoing signs of Dropsy, and ho had some of her special

tea containing some 2@ herbs, one being -o.glove# *o, 7ithering then got his friend to sell him the

special tea, so he co!ld investigate the plant properly# 5ne of his patients as a breer ho as

s!ffering from sollen limbs and an irreg!lar heartbeat# $fter a fe doses of 7itherings digitalisso!p, he became healthy and his p!lse became more reg!lar# B!t his ne.t patient died so 7ithering

gave !p# B!t then 7ithering as pers!aded to rene his investigations, and he led onto important

research hich fo!nd that the active ingredient in the fo.glove is a single chemical called digitalin#

Today, a potetial ne dr!g m!st pass a series of tests before it is safe to !se# t has to be proven to

be effective, safe, and capable of ma"ing profit#

2.!. 4elate the structure of seeds to their role in the dispersal and sur*i*al of the plant

(adaptations for dispersal, protection and nutrition of the embryo)

*eeds are vital to the s!rvival of a plant, they: protect the embryo

aid dispersal

provide n!trition for the ne plant

The embryo develops into three distinct parts' a radicle (yo!ng root), a pl!m!le (yo!ng shoot) and

one or to cotyledons (seed leaves)#

n some species, the stored food in the seed remains o!tsice the embryo in storage tiss!e called the

endosperm# The o!ter layers of the ov!le become lignified forming a to!gh seed coat (testa) hich

helps to protect the embryo#


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*ome seeds ill germinate as soon as s!itable conditions prevail b!t others are dormant and ill not

immediately prevail, b!t others are dormant and ill not germinate immediately even in a

favo!rable environent#

*ome ays hich dormancy can be bro"en incl!de:

8# E.pos!re to an e.tended period of chilling

2# ntense heat=# /hemical reaction in an animals g!t

7hen a seed germinates, cells in the embryo absorb ater and the seed coat r!pt!res# This brings

abo!t metabolic changes in the seed, and prod!ction of plant groth s!bstances are sitched on,

hich ca!se the secretion of en+ymes that brea" don the food reserves# ?ipases brea" don the

stored lipids and proteases brea" don the proteins in the food, all to give amino acids#

*eeds come in all shapes and si+es, hich allo the seed to be idely dispersed# There are fo!r

main methods that seeds rely on to carry them to their ne location:

7ind dispersal

$nimal dispersal 7ater dispersal

*elf dispersal

2.!./ Describe uses of starch and plant oils for humans (diet, packaging, glues, absorbent

materials, fuels) and eplain how the use of plant products can make resource utilisation more

sustainable

*tarch can be !sef!l in o!r diets, b!t it also has many other !ses, incl!ding adhesives, paints,

te.tiles, and mo!sses# They are !sef!l beca!se hen the starch gran!les are heated in ater, they

sell and absorb the ater hich thic"ens the li!id, and this process is the basis of c!stard and

allpaper paste#

$t certain temperat!res, if the press!re is raised, starch can form a plastic mass hich is !sef!l for

pac"aging# -!rthermore, plants can be !sed as oils, for e.ample vegetable oil in diesel engines#

0oever, if e !se plant oils as f!el, then b!rning oil based fossil f!els releases carbon dio.ide

hich can lead to global arming, and oil reserves event!ally r!n o!t# 0oever, if e !se plant

based prod!cts, it can red!ce this problem beca!se e can plant ne plants in replace of the ones

e !se#

2.!.10 Describe how the genetic modification of plants is similar to but distinct fromcon*entional breeding

*pecial plants come from chemical or physics m!tations, environmental factors s!ch as gamma

radiation, hich increase the rate of m!tations so increase the chances of prod!cing plants ith ne

characteristics# Today, a plant breeder ill identify individ!al plants ith desired characteristics,

and if the plant has both male and female parts, these then can be self pollinated# The seeds are then

gron, and the best offspring are selected and again self pollinated# f this process is repeated

several times the genetic variation is red!ced and becomes more homo+ygo!s#


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f the plant can not self pollinate, then genetically modified crops can be !sed# This is the process

hereby desired characteristics (genes) are inserted into the plants D%$# This is done by:

$ bacteri!m contains plasmids of D%$ hich, hen inserted into the plant cells, become

incorporated into the chromosomes of the plant cells# *o, if the ne genes are inserted into

the plasmid, then they can be carried directly to the D%$ of the plant#

6ir!ses can also be !sed in a similar ay#

D%$ g!n

The scientists need a method of screening to find o!t hich plant cells have the ne gene# They

!s!ally do this by incorporating a gene for antiobiotic resistance, often called a mar"er gene# The

plant cells are then inc!bated ith the antibiotic, and the only cells hich s!rvive are those hich

have ta"en the ne gene and are resistant#

The 4& plant cells are then c!lt!red in agar ith n!trients and plant groth s!bstances to prod!ce

ne plants# This micropropagation can m!ltiply a single cell to form a mass of plant cells#

2.!.11 Discuss the scientific arguments for and against the use of genetically engineered plants

(impro*ed plant 6uality, enhanced yield, and conse6uences for the en*ironment and health)2.!.12 Discuss the social, and ethical arguments for and against the use of genetically

engineered plants

The main health concerns ith 4& crops is that there co!ld be a transfer of antibiotic resistance to

microbes, and also the formation of harmf!l prod!cts by the ne genes# 0oever, it has to be said

that the !se of 4& crops ma"es plants more idely available, and increases yield# People have the

right to choose hat they ant to eat#The religio!s aspect s!ggests that genes sho!ld not be altered

beca!se god created !s they ay that e sho!ld be made# -!rthermore, altho!gh yield is increased,

poorer co!ntries o!ld not be able to afford to have 4& crops#

2.!.1! 7utline the causes of global warming 8 including the role of green house gases in the

green house effect. Describe the sources of carbon dioide and methane !, their possible

role in global warming and how their le*els might be controlled


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$ rise in greenho!se gases trap the s!ns energy and "eep heat from escaping the Earths s!rface#

&ethane is an e.ample of a greenho!se gas, it is prod!ced by anaerobic decay of organic matter,

decay of domestic aste, and the decomposition of animal aste#t is also prod!ced in the digestive

systems of animals s!ch as cattle and released hen they belch and fart# There is also evidence for

increase in carbon dio.ide and increase in global temperat!re, hoever there is no proof that one

ca!ses the other# /arbon dio.ide is increased by the !se of cars and poer stations#

&ethane can be loered by better aste recycling and by !sing a biof!els (here one greenho!segas changes into to less serio!s ones)# /arbon dio.ide can be red!ced by not !sing cars, and

red!cing electricity and gas !se#$lso, by reafforestation#

2.!.1+ 4ecall the role of the carbon cycle in regulating atmospheric carbon dioide le*els


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2.!.1 Describe and analyse data from different types of e*idence for and against global

warming including temperature records, pollen in peat bogs and dendrochology and

appreciate that scientific e*idence must be supported by e*idence

Dendrochology is a form of tree ring analysis hich determines the age of the tree# This is beca!se

each year the tree forms ne .ylem vessels# The o!termost ring ill have come from most recent

groth, and if yo! co!nt inards yo! can date the year each ring as formed#

Peat bogs can also be !sed to determine climate conditions ears ago# &any obects are fo!nd to be

preserved in peat# Pollen grains are partic!larly ell preserved#

Plants prod!ce pollen in vast amo!nts

Each species of pollen pord!ces a distinctive type of pollen

Peat forms in layers, the deeper the layer, the older the peat

Each species of plant has a partic!lar optim!m condition hich it flo!rishes best, if e find

pollen from a species hich favo!rs armer conditions, e can say that the peat as laid

don in a armer climate#

2.!.1-Eplain how climate change (rising temperature, changing rainfall patterns, and

change in seasonal cycles) can affaect plants and animals (distribution of species, de*elopment

and life cycles)

$nimals are li"ely to be affected by changing climates# -or e.ample, an animal may breed at a

certain time of the year in cooler conditions, if the temperat!re increases, then this co!ld res!lt in

animals being born earlier and !ndereight, red!cing the chances of s!rvival# -!rthermore,

changing of the seasons is a nat!ral indicator for some animals, for e.ample for migration# *o if this

nat!ral system changes, then this co!ld ca!se conf!sion and possibly less chance of s!rvival# $lso,

sometimes the hatching or birth of animals is synchronised ith ma.im!m food availability, so if

increase in temperat!re affects hatching of food so!rces, then there ill not be eno!gh food

available, leading to lo s!rvival rates#

2.!.1 Eplain the effect of increased temperature on the rate of en9yme acti*ity

ncrease in temperat!re is good for reactions, hoever, higher temperat!res are not !sef!l# This is

d!e to the rate of en+yme activity# Temperat!re effects the rate of an en+yme catalysed reaction# $t

lo temperat!res the reaction is very slo, this is beca!se the en+yme and s!bstrate molec!lesmove sloly and dont collide very often# $s the temperat!re increases, there are more collisions,

so the s!bstrate binds ith the en+ymes active site more fre!ently (so increase the rate of reaction)#

0oever, this happens !ntil an optim!m temperat!re is reached here ma.im!m rate of reaction

occ!rs# The shape of the active site is lost and the en+yme s!bstrate comple. no longer forms, so no

reaction can occ!r# The en+yme has become denat!red#


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