IB BIOLOGY TOPIC 1 CELLS

7/18/2019 IB BIOLOGY TOPIC 1 CELLS

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2.1.1 Outline the cell theory.

• All living things are made from cells – they are a basic unit of structure

• Smallest unit of life

• Derived from pre-existing cells by division

• Contain a blueprint for growth, development & behaviour

• Site of all metabolism

2.1.2 Discuss the evidence for the cell theory.Scientists looed at the structures of organisms under microscopes and found they were allmade form small units called cells!

"he cells were able to survive on their own for a period of time, but nothing smaller was ableto survive!#xperiment – sterilise two samples of nutrients! Seal one and expose the other to air! $bserve

that the organisms must arise from other existing organisms% cells!

2.1.3 State that unicellular organisms carry out all the functions of life.

2.1.4 Compare the relative sizes of molecules, cell memrane thic!ness, viruses,

acteria, organelles and cells, using the appropriate S" unit.

millimeter 'mm( ) *-+ meters micrometer 'm( ) *-+ millimeters # *- meters nanometer 'nm( ) *-+ micrometers ) *-. meters

/olecule nm "hicness of cell membrane * nm0iruses ** nm1acteria m$rganelles up to * m#uaryotic cells up to ** m

2.1.$ Calculate the linear magni%cation of dra&ings and the actual size ofspecimens in images of !no&n magni%cation.

2.1.' ()plain the importance of the surface area to volume ratio as a factor limitingcell size.0olume increases at a faster rate than surface area! As volume increases, the surface area 2

volume ratio decreases and the cell3s interior has decreasing access to the external

environment! "he cell becomes less e4cient as substances must be transported in & out!

Di5usion in% out is much slower!

2.1.* State that multicellular organisms sho& emergent properties.

"he properties are worth more than the sum of individual parts!

2.1.+ ()plain that cells in multicellular organisms dierentiate to carry out

specialized functions y e)pressing some of their genes ut not others.

• 6enes - a speci7c region of a chromosome which determines the development of a

speci7c characteristic!

• 8hen a cell di5erentiates, particular genes are activated, resulting in a specialised cell!

• -otipotency - a cells potential to specialise

• 9ighly specialised cells are unable to divide• Specialised cells are dependent upon each other

2.1. State that stem cells retain the capacity to divide and have the aility to

dierentiate along dierent path&ays.

$riginal cell



Stem cells are pluripotent and can produce di5erentiate into many cells!

2.1.1/ Outline one therapeutic use of stem cells.

1one marrow cells can be harvested before chemotherapy and replaced afterwards to ensure

the patient has an ample supply of red and white blood cells, as the stem cells found in bone

marrow are illed during chemotherapy!

2.2.1 Dra& and lael a diagram of the ultrastructure of Escherichia coli 0E. coli asan e)ample of a pro!aryote.

2.2.2 nnotate the diagram from 2.2.1 &ith the functions of each named structure.

2.2.3 "dentify structures from 2.2.1 in electron micrographs of E. coli .

#scherichia Coli

2.2.4 State that pro!aryotic cells divide y inary %ssion.

Cell 8all :rotects the cell from structuraldamage 'pressure-wise & external

damage(

/aintains the cell3s shape:lasma

/embran

e

Semi permeable membrane

Controls entry & exit

:ili 9elps cell connect to others during

exchange of D;A<ibosome

s

Synthesise protein

Cytoplas

m

=elly-lie substance

Site of metabolism>lagella /ovement



2.3.1 Dra& and lael a diagram of the ultrastructure of a liver cell as an e)ample

of an animal cell.

2.3.2 nnotate the diagram from 2.3.1 &ith the functions of each named structure.

2.3.3 "dentify structures from 2.3.1 in electron micrographs of liver cells.

2.3.4 Compare pro!aryotic and eu!aryotic cells.

(u!aryotes ro!aryotesChromosomes enclosed in nuclear envelope ;aed D;A in the cytoplasm/itochondria for A":s ;o mitochondria?onger ribosomes '@*S( Shorter ribosomes '*S(/any organelles >ewer organelles

2.3.$ State three dierences et&een plant and animal cells.

Characteristic lant nimalCell wall /ade from cellulose none

<ough

#ndoplasmi

c <eticulum

Contains ribosomes!

Synthesises proteins for use

outside the cell?ysosome 1rea down waste & cellular

debris using digestive

enBymes:lasma

/embrane

Controls entry & exit

Semi permeable<ibosomes Synthesise proteins according

to <;A orders!

>ree oating or on <#< "wo subunits

6olgi :rocesses materials produced

in the cell for intra%extra

cellular use;ucleus Control centre of the cell

Contains hereditary

information/itochondri Site of respiration – converts



Chloroplasts sed for photosynthesis none0acuole ?arge, permanentE 7lled with

uid

Small temporary vacuoles

Centrosome none $utside nucleus:lasticity% Cell shape >ixed shape due to cell wall <ounded, able to change

shape#nergy storage Starch 6lycogen

2.3.' Outline t&o roles of e)tracellular components.

:lant Cell 8all

• :rotects the cell from pressure & external damage!

• Strength comes from cellulose arranged in micro7brils!

• :revents excessive osmosis!

• 6ives structure & the ability to stand against gravity

Animal 6lycoproteins

• Attached to the membrane• sed in adhesion, support & movement



2.4.1 Dra& and lael a diagram to sho& the structure of memranes.

Structure unctionFntegral :rotein :ermanent, allows facilitated di5usion & active transport 'if it is a

channel(:hospholipid 1ilayer "wo layers of globular proteins, allows selective entry and exitCytoseleton Sca5old of 7brous proteins6lycoprotein :rotein with polysaccharide attached, acts as receptor:eripheral :rotein "emporary, allows entry 'outer( & exit 'inner( for speci7c

substancesCholesterol <educes uidity

2.4.2 ()plain ho& the hydrophoic and hydrophilic properties of phospholipids help

to maintain the structure of cell memranes.



"he phospholipids are made from a phosphate group connected to a glycerol and two fattyacid tails!

"he phosphate head is hydrophilicE they are attracted to water "he fatty acid tails are hydrophoicE they are repelled by water!Fn a watery environment, the phospholipids will automatically form a bilayer as above!

"he cell will therefore remain stable but allow exibility, as the phospholipids are in a uid!

2.4.3 5ist the functions of memrane proteins.

:roteins are used as hormone binding sites, electron carriers, pumps for active transport,

receptors, channels for passive transport, and enBymes

2.4.4 De%ne difusion and osmosis!



:assive di5usion – unaided movement of particles from an area of high concentration to low

concentration

$smosis – unaided movement of water through a semi-permeable membrane from an area of

high water potential to low water potential!

2.4.$ ()plain passive transport across memranes y simple diusion and

facilitated diusion.

:assive Di5usion:articles move through the semi-permeable lipid bilayer through simple di5usion until the

concentration on both sides is even! 9ydrophobic molecules di5use inwards through this

method!

>acilitated Di5usionChannel proteins allow hydrophilic & charged molecules in 'inside of cell is hydrophobic(

2.4.* ()plain ho& vesicles are used to transport materials &ithin a cell et&een the

rough endoplasmic reticulum, 6olgi apparatus and plasma memrane.

:roteins are synthesised in the rough endoplasmic reticulum by ribosomes! 0esicles transport

the protein to the golgi apparatus, and then to the plasma membrane! "he vesicle fuses with

the membrane and expels its contents outside the cell! "his is exocytosis! "he membrane

then pinches inwards and the vesicle detaches! "his is endocytosis!



2.4.+ Descrie ho& the 7uidity of the memrane allo&s it to change shape, rea!

and re8form during endocytosis and e)ocytosis.

"he phospholipids which mae up the membrane are in a uid state! "his allows them to

move, change shape, and allow vesicles to fuse with it! "his is critical during endocytosis andexocytosis as it means that substances are able to enter & exit the cell!

2.4.' ()plain the role of protein pumps and - in active transport across

memranes.

Active transport is used to transport substances against a concentration gradient! "he protein

pump reGuires energy to open and close, which it receives from A":s! ;ote that protein

pumps are speci7c!



2.$.1 Outline the stages in the cell cycle, including interphase 061, S, 62, mitosis

and cyto!inesis



6 – Cell grows and matures

S – D;A is replicated in preparation for mitosis

6H – Cell grows further and prepares for mitosis

/itosis – Divided into prophase, metaphase, anaphase& telophase! Daughter cells3 genomes are separated!

Cytoinesis – "he cytoplasm divides to create twodaughter cells! Fn animals, the cell membrane divides and in plants, aplate between the daughter cell s is formed!

2.$.2 State that tumours 0cancers are the result of uncontrolled cell division and

that these can occur in any organ or tissue.

2.$.3 State that interphase is an active period in the life of a cell &hen many

metaolic reactions occur, including protein synthesis, D9 replication and an

increase in the numer of mitochondria and:or chloroplast

2.$.4Descrie the events that occur in the four phases of mitosis 0prophase,

metaphase, anaphase and telophase.

"nterphase

Fncludes 6, S, and 6H

;ew organelles grow during 6!

Chromosomes replicate & coil to form

chromatids during S! Cell grows in

preparation for mitosis during 6H ! rophase

;uclear membrane breas down,

nucleolus disintegrates2. ;etaphase

Centrioles move to polesSpindle appearsChromatids line up

3. naphaseSpindle retreats & chromatids split,

forming two sets of D;A4. -elophase

;uclear membrane reforms;ucleolus reforms

Chromatids decondense to formchromatids

$. Cyto!inesisCell pinches in half Cytoplasm divides

2.$.$ ()plain ho& mitosis produces

t&o genetically identical nuclei.

During the S phase of interphase, the D;A is duplicated in the form of sister chromatids

held together by a centromere! During mitosis, the chromatids are separated to opposite

sides of the cell, before it is divided into two daughter cells! "he daughter cells are thusgenetically identical!

2.$.' State that gro&th, emryonic development, tissue repair and ase)ual

reproduction involve mitosis.

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IB BIOLOGY TOPIC 1 CELLS