Topic 1

Question 1

Discuss possible exceptions to cell theory. 4 marks

Answer 1

skeletal muscle fibers are larger/have many nuclei/are not typical cells

fungal hyphae are (sometimes) not divided up into individual cells

unicellular organisms can be considered acellular

because they are larger than a typical cell/carry out all functions of life

some tissues/organs contain large amounts of extracellular material

e.g. vitreous humor of eye/ mineral deposits in bone/ xylem in trees/other example

statement of cell theory/all living things/most tissues are composed entirely of true cells

Question 2

Eukaryotic cells have intracellular and extracellular components. State the functions of one named extracellular component. 4 marks

Answer 2

name of component: 1 max

e.g. plant cell wall/cellulose/interstitial
matrix/basement membrane/glycoprotein/bone matrix;
functions: 3 max
EITHER

e.g. (plant cell wall) strengthens/supports the cell/plant (against gravity);
prevents the entry of pathogens;
maintains the shape of plant cells;
allows turgor pressure/high pressure to develop inside the cell;
prevents excessive entry of water to the cell;
OR
helps cells to stick together/adhere;
needed to hold cells/tissues together / example of cells/tissues holding together;
forms interstitial matrix / forms basement membrane to support single layers of cells;
e.g. around a blood capillary;
forms (part of the) filtration membrane in the glomerulus;

Question 3

Explain how the surface are to volume ratio influences cell sizes. 3 marks

Answer 3

small cells have larger ratio (than larger cells)/ratio decreases as size increases

surface area/membrane must be large enough to absorb
nutrients/oxygen/substances needed

surface area/membrane must be large enough to excrete/pass out waste products

need for materials is determined by (cell) volume

cell size is limited (by SA/Volume ratio)/cells divide when they reach a certain size

reference to diffusion across/through membrane/surface area

Question 4

Outline differentiation of cells in a multicellular organism. 4 marks

Answer 4

differentiation is development in different/specific ways

cells carry out specialized functions/become specialized

example of a differentiated

cell in a multicelluar organism
cells have all genes/could develop in any way

some genes are switched on/expressed but not others

position/hormones/cell-to-cell signals/chemicals determine how a cell develops

a group of differentiated cells is a tissue

Question 5

Describe the importance of stem cells in differentiation. 3 marks

Answer 5

stem cells are undifferentiated cells;

embryo cells are stem cells;

stem cells can differentiate in many/all ways / are pluripotent/totipotent;

differentiation involves expressing some genes but not others;

stem cells can be used to repair/replace tissues/heal wounds;

Question 6

State one function of each of the following organelles: lysosome, Golgi apparatus, rough endoplasmic reticulum, nucleus, mitochondrion. 5 marks

Answer 6

lysosome: hydrolysis/digestion/break down of materials (macromolecules)

Golgi apparatus: synthesis/sorting/transporting/secretion of cell products

rough endoplasmic reticulum: site of synthesis of proteins (to be secreted)/ intracellular transport of polypeptides to Golgi apparatus

nucleus: controls cells activities/mitosis/replication of DNA/transcription of DNA (to RNA)/directs protein synthesis
mitochondrion: (aerobic) respiration/generates ATP

Question 7

Distinguish between the structure of plant and animal cells. 6 marks

Answer 7

Award 1 mark per difference plant cells

have cell walls, animals do not

have plastids/ chloroplasts, animals do not

have a large central vacuole, animals do not

store starch, animal cells store glycogen

have plasmodesmata, animal cells do not

animal cells

have centrioles, plant cells do not

have cholesterol in the cell membrane, plant cells do not

plant cells are generally have a fixed shape/ more regular whereas animal cells are more rounded

Question 8

Using a table, compare the structures of prokaryotic and eukaryotic cells. 5 marks

Answer 8

P: prokaryotic cells; E: eukaryotic cells

DNA: P: naked/loop of DNA; E: associated with protein/histones/nucleosomes/DNA in chromosomes

location of DNA: P: in cytoplasm/nuceloid/no nucleus; E: within a nucleus/nuclear membrane

membrane bound organelles: P: none; E: present

ribosomes: P: 70S ; E: 80S

plasma membrane: P & E: same structure within both groups

cell wall: P: peptidoglycan/not cellulose/not chitin; E: cellusose/chitin/not peptidoglycan

respiratory structures: P: no mitochondria; E: mitochondria

pili: P: pili present E: pili absent;
plasmids: P: plasmids (sometimes) present E:plasmids absent;
flagella: P: flagella solid E: flagella flexible/membrane-bound;