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Question 1

Describe the role of mitosis

Answer 1

makes cells / cell division; A nuclei
genetically identical / clone;
	growth;	R ‘of cell’
repair (of tissues);	R ‘of cell’
asexual reproduction;

Question 2

Which processes must occur in a cell during interphase before mitosis can take place?

Answer 2

sreplication of DNA;
centrioles replicate;
production of (named) organelles;
	protein synthesis; A named e.g.
RNA / nucleotide, synthesis;
respiration / active transport / named e.g. of usual cellular activity;
	AVP; e.g.	semi-conservative
	chromosome = 2 chromatids

Question 3

stage of mitosis where

chromosomes split at centromeres

Answer 3

(early) anaphase

Question 4

stage of mitosis where

Chromosomes become visible.

Answer 4

prophase;

Question 5

stage of mitosis where

Nuclear envelope re-forms.

Answer 5

telophase;

Question 6

stage of mitosis where

Chromatids move to opposite poles of the cell.

Answer 6

anaphase;

Question 7

stage of mitosis where

Chromosomes line up along the equator of the spindle.

Answer 7

metaphase;

Question 8

Plant cells are also eukaryotic.

Outline the function(s) of each part of a plant cell.

Answer 8

nucleus / DNA
1	controls, activities of cell / transcription / named activity / cell division;
2	contains genetic information that can be transmitted to next generation;
	nucleolus
3	produces, ribosomes / rRNA;
	smooth ER
4	makes / transports, lipids / steroids / hormones; A named plant e.g.
	rough ER / ribosomes
5	protein synthesis;
 
	rough ER
6	transport of proteins;
	Golgi
7	processes, molecules / proteins; AW
8	use in secretion;
9	lysosome formation;
	lysosome
10	hydrolytic / digestive, enzymes;
11	breakdown, organelles / cell / ingested material;
	mitochondria
12	formation ATP / suitable energy ref.;
13	aerobic respiration;

plasma (cell surface) membrane 14	controls exchange between cell and environment / selectively permeable; R water 15	receptors for, cell recognition / attachment; 16	fluid to allow, endocytosis / exocytosis;
cell wall 17	gives, cell shape / strength / support; 18	prevents bursting (when water enters cell by osmosis); 19	fully permeable;
chloroplast 20	photosynthesis; 21	chlorophyll / pigment, absorbs light;

vacuole / tonoplast 22	reservoir of, salts / sugars / waste / pigment / other e.g.; 23	ref. to, turgor / support / controlling Ψ;
starch grain / amyloplast 24	storage;
cytoplasm 25	site of chemical reaction(s) / correct e.g.; 26	AVP; 27	AVP;  
for further detail of function e.g.	protein, channels / carriers, to transport, ions / polar substances
phospholipid (bilayer) transports lipid soluble substances
ref. waterproofing cell wall (lignin / suberin)
mitochondria involved in lipid synthesis
addition of carbohydrate to protein to form glycoprotein
plasmodesma

Question 9

Explain why red blood cells may burst when they are placed in a solution that has a lower concentration of salts than blood plasma.

Answer 9

lower, water / solute, potential inside cell / converse;
water enters;
(enters) by osmosis / down Ψ gradient;
increase in pressure;
membrane cannot withstand pressure / no cell wall to prevent bursting;

Question 10

Suggest why different red blood cells haemolyse at different salt concentrations

Answer 10

each rbc has (slightly) different, water potential / solute concentration

Question 11

the main process by which potassium ions enter the carrot cells.

Answer 11

active, transport / uptake
oxygen required for, uptake / respiration / ATP production;
A release / provide, energy

Question 12

Suggest an explanation for the uptake of potassium ions in the absence of oxygen.

Answer 12

passively / by diffusion;
residual ATP;
anaerobic respiration;

Question 13

the function of the cilia on the diagram in the gas exchange system.

Answer 13

cilia, beat / waft; R ‘hairs’ A ciliated epithelium, sweeps / AW
move mucus;
particles / bacteria / dust / spores / pathogen / microbe, in mucus;
treat ‘dirt’ as neutral
(moves) away from alveoli / upwards / towards trachea / towards throat /
towards mouth / out of lungs / out of bronchioles

Question 14

explain the following observations made on the bronchioles of an asthmatic during an attack of asthma.
The bronchioles fill with mucus.

Answer 14

ef to (secretion / release of) histamine;
mucus is not moved / AW;
more goblet cells;
(goblet cells secrete / produce) more mucus / excess mucus;
fewer cilia (per cell); A stunted, damaged, destroyed R dead

Question 15

explain the following observations made on the bronchioles of an asthmatic during an attack of asthma.
The cross sectional area of the air spaces in the bronchioles decreases.

Answer 15

thicker / more, (smooth) muscle; A larger / expands R swollen, swells
(muscle) contracts; R constricts, spasm A ‘muscle tenses’
connective tissue, swells / enlarges / fills with fluid;
lining of bronchiole thrown into deeper folds /

Question 16

Explain how single-celled organisms like Chlamydomonas obtain water from their external environment.

Answer 16

osmosis;
down water potential gradient / from high to low water
potential / implied;
ref to partially / differentially / selectively, permeable membrane;

Question 17

Explain why a large multicellular organism like a tree needs a water transport system whilst Chlamydomonas(single cell organism) does not.

Answer 17

distance in tree is greater / AW;
e.g. roots far from aerial parts / AW;
not all tissues / cells in contact with water / AW;
diffusion too slow / AW;
AVP; e.g. outer layers waterproofed / ions carried in water /
Chlamydomonas has large surface area:volume

Question 18

Definition: transpiration

Answer 18

loss, of water vapour / by evaporation;
diffusion into, atmosphere / air / environment / out of plant;
via stomata or from, leaves / aerial parts;

Question 19

Explain how transpiration results in the movement of water up a plant stem.

Answer 19

loss of water from mesophyll;
cell walls;
more drawn from, cytoplasm / cell / AW;
cohesion of water molecules;
hydrogen / H, bonds;
water under tension / ref to hydrostatic pressure gradient implied;
A water ‘pulled’ / ‘drawn’ R sucked
via, symplast / apoplast / vacuoles / description / AW;
(water from) xylem / xylem vessels;
ref to water potential gradient;

Question 20

Explain why there are valves at the pulmonary valve and aorta

Answer 20

A / atrium, only pushes, to ventricle / short distance / AW;
A effect of gravity
C / left ventricle, pushes all round body / to systemic system / AW;
D / right ventricle (only) pushes to lungs / to pulmonary system / AW;

Question 21

Describe how the heart beat is initiated and how the contractions of the four chambers are coordinated.

Answer 21

1 cardiac muscle is myogenic / description;
2 SAN / sinoatrial node / pacemaker;
3 (in wall of) right atrium;
4 wave of electrical activity / impulse / depolarisation / excitation /AW;
5 spreads across atria / causes atria to contract;
6 stopped / AW (by, fibres / septum), between atria and ventricles;
7 delay allows atrial systole to be completed (before ventricular systole);
8 atrioventricular node / AVN;
9 impulse passes down / to, Purkyne (Purkinje) fibres / bundle of His;
10 contraction from base upwards;
11 both ventricles contract together / AW;
12 AVP; e.g. external nervous control in response to, temp / CO2 / etc
delay of 0.1 s at AVN
hormone control

Question 22

Explain what is meant by partial pressure of oxygen

Answer 22

equivalent to) concentration / AW, of oxygen in, atmosphere / air / tissues;
proportion of atmospheric pressure produced by oxygen / AW;
at high altitude, atmospheric pressure is lower; ora A ‘air is thinner’
therefore pO2 is lower / 15 kPa v 21 kPa; ora

Question 23

Describe what would be likely to happen to people who move to high altitude if their red blood cell counts did not increase.

Answer 23

haemoglobin / rbc / blood less saturated with oxygen / less oxygen
carried in blood / AW;
altitude sickness;
hypoxia / anoxia; A shortage of oxygen to tissues
changes in, breathing pattern / heart rate / pulse rate;
dizziness / weakness / disorientation / hallucinations / headaches / AW;
(possible) death / coma;
brain damage / lung damage / fluid accumulation or oedema in these
organs / ref to arteriole / capillary dilation in these organs;
AVP; e.g. ref to alkalaemia / described / alkaline urine / raised blood pH

Question 24

The synthesis of red blood cells is stimulated by the hormone erythropoetin (EPO) which is secreted by the kidneys. Some long distance athletes have been known to take a course of EPO as part of a training programme.
Suggest why some athletes have taken erythropoetin.

Answer 24

more haemoglobin;
get more oxygen round body;
more / longer, aerobic respiration (when exercising); ora for anaerobic
reduces, lactate / lactic acid; A delays oxygen debt;
more, ATP / energy release; R producing / making energy
enhanced performance / AW; A exercise for longer or harder
increased carbon dioxide removal;
ref to indetectability (as a natural product);