Essay Questions

Question 1

Discuss the factors that affect enzyme activity

Answer 1

1. Enzymes are catalysts/seed up metabolism/chemical reaction/lower activation energy
2. Temperature: enzymes have an optimum temperature/temperature at wrich they work best/work best at 37°C (or labelled graph to illustrate)
3. pH: all enzymes have an optimum pH/pH at which they work best (or labelled graph to illustrate)
4. Denaturing: a change occurs in the structure/shape/active site of the enzyme at high temperatures/when the pH changes
5. Inhibitors: slow up/stop enzyme activity
6. Competitive inhibitors: allach to/block the active site so keeping out the substrale molecule OR inhibitor competes with substrate for active site
7. Non-competitive inhibitors: attach to another part of an enzyme and changing the shape of the active site/enzyme (so the substrate molecule does not fit)
8. Substrate concentraton: increasing substrate concentration increases activity until a point when activity levels off (or labelled graph to lustrate)
9. Explanation that activity levels off when al enzyme active sites are reacting with substrate molecules/enzymes are working at fastest rate possible
10. Enzyme concentration: increasing enzyme concentration increases the rate of reaction (or labelled graph to illustrate)
11. Explanation that activity increases due to more active sites being added

Question 2

Give an account of cell differentiation under the following headings.
(i) Stem cells;
(ii) Somatic cells;
(iii) Germline cells.

Answer 2

Stem cells

1. Differentiation occurs when unspecialised cells become specialised (to perform a specific function)
2. Stem cells are unspecialised cells that can (divide to) form more stem cells
3. Embryonic stem cells can differentiate / develop into all / any cell types
4. Tissue / adult stem cells give rise to a more limited range of / fewer cell types
5. Example given such as stem cells in the (red) bone marrow only produce blood cells / named blood cells
6. A differentiated cell only has a few genes switched on / produces specific proteins

Somatic cells

7. Somatic cells form different types of body tissue
8. Body organs are formed from a variety/mixture of these tissues
9. (The nucleus of a) somatic cell divides by mitosis (to maintain the diploid chromosome number)

Germline cells

12. The (nucleus of a) germline cell can divide by mitosis to produce more germline cells / diploid cells
13. (The nucleus of a) germline cell can divide by meiosis to produce haploid gametes/ cells.
14. Mutations in germline cells can be passed on to offspring (whereas mutations in somatic cells are not).

Question 3

Describe protein synthesis under the following headings:
(i) Transcription of DNA;
(ii) Translation of mRNA.

Answer 3

Transcription of DNA
1. DNA unzips/hydrogen bonds break/DNA strands separate.
2. RNA nucleotides pair with DNA bases.
3. Guanine pairs with cytosine, uracil pairs with adenine. (not base letters)
4. Sugar phosphate bonds form/sugar phosphate backbone forms.
5. This requires ATP/enzymes/RNA polymerase
6. Introns/non-coding regions are removed from mRNA/the primary transcript

Translation of mRNA
7. mRNA attaches/moves to the ribosome.
8. tRNA carries amino acid to mRNA /ribosome.
9. Each tRNA molecule is attached to a specific amino acid.
10. tRNA/mRNA has a anticodon/codon of three bases
11. Anticodon binds to / aligns with codon.
12. Order of codons/bases determines the order of amino acids.
13. Peptide bonds form between amino acids.
14. Ribosome moves along the mRNA strand.
15. (Translation/process) begins at a start codon/ends at a stop codon.

Question 4

Describe aerobic respiration under the following headings:
(i) The citric acid cycle;
(ii) The electron transport chain.

Answer 4

The citric acid cycle

1. Pyruvic acid/pyruvate is converted to an acetyl group.
2. The acetyl group combines with coenzyme A (to form acetyl coenzyme A)
   2a. Note - Breakdown of pyruvic acid to acetyl coenzyme A gets 1 mark only.
3. Acetyl coenzyme A combines with oxaloacetate/oxaloacetic acid to form citrate/citric acid.
4. Citrate/citric acid is converted back into oxaloacetate/oxaloacetic acid / 4 carbon compound.
5. Carbon dioxide is released.
6. (Some) ATP is produced.
7. Dehydrogenase (enzymes) remove hydrogen (ions)/(high energy)
   electrons.

The electron transport chain
8. Hydrogen/electrons are passed to (coenzyme) NAD.
9.NADH release electrons to the electron transport chain.
10. Electrons are passed/cascade along the chain of carriers/proteins.
11. Energy is released which pumps hydrogen ions across the (inner)
mitochondrial membrane.
12.The return flow of hydrogen (ions) synthesises ATP.
13. Using the enzyme ATP synthase.
14. Oxygen acts as the final electron/hydrogen acceptor / combines with hydrogen.
15. Water is formed.

Question 5

Describe the structure of DNA and the process of DNA replication.

Answer 5

Structure
1 DNA is composed of nucleotides containing deoxyribose (sugar), phosphate and base.
2 There is a sugar phosphate backbone.
3 The four bases are adenine, thymine, cytosine and guanine.
4 Cytosine bonds/pairs with Guanine and Adenine bonds with Thymine.
5 Bases/two strands are joined by hydrogen bonds.
6 Strands are anti-parallel/run in opposite directions/3’ to 5’ and 5’ to 3’.j
7 DNA/two strands form a double helix (shape).

Replication
DNA/double helix is unwound /unzipped.
A primer is needed at the start of replication/attaches to DNA strand.
C DNA polymerase adds
nucleotides to the 3’ end (of a new/growing strand/primer).
dOne strand is replicated continuously and the other strand is replicated in fragments/discontinuously.
e The strand replicated in fragments is joined together by ligase.

Question 6

Describe the structure of RNA and the process of transcription.

Answer 6

Structure
1 RNA is single stranded.
2 It is composed of nucleotides containing ribose (sugar), phosphate and base.
3 The four bases are uracil, adenine, cytosine and guanine.
4 Groups of three bases/nucleotides form codons in mRNA/anticodons in tRNA.
5 Start/stop codons exist.
6 tRNA folds due to base pairing/has an attachment
7 site for a specific amino acid. rRNA (and protein) forms a ribosome.

Transcription
a. Transcription occurs in the nucleus.
b. RNA polymerase forms mRNA/ unwinds and unzips DNA.
c. (Complementary) base pairing, occurs - adenine with uracil, guanine with cytosine.
d. The primary transcript/mRNA contains introns and exons.
e Introns are removed/ exons remain after (RNA) splicing.
f (Splicing)forms the mature transcript/mRNA.

Question 7

Describe hormonal control of the menstrual cycle under the following headings:
(i) events leading to ovulation;
(ii) events following ovulation.

Answer 7

i) 1. Pituitary gland secretes/ produces FSH/LH.
2. FSH stimulates growth of follicle (in the ovary).
3.Follicle/ovary produces oestrogen.
4. oestrogen stimulates growth/ repair proliferation / thickening of endometrium/ uterus lining.
5. Oestrogen stimulates production of LH.
6. LH (surge) brings about ovulation/release of the egg.
7. Rising/high levels of oestrogen inhibit FSH production.
8. This is negative feedback

(di)
a.The follicle develops into the corpus luteum.
b.Corpus luteum secretes progesterone (and ostrogen).
c. Progesterone maintains/ increases/thickens the endometrium/uterus lining.
d. Progesterone inhibits FSH/ LH production.
e. Progesterone/oestrogen levels decrease towards the end of the cycle.
f. This/corpus luteum degeneration triggers menstruation/breakdown of endometrium.

Question 8

Describe the cardiac cycle under the following headings:
(i)the conducting system of the heart;
(ii)nervous control of the cardiac cycle.

Answer 8

1. Pacemaker/SAN contains auto rhythmic cells/is where the heart beat originates/is found in the right atrium.
   2 • Impulse/wave of excitation spreads across the atria/cause the atria to
2. (Impulses) reach/stimulate AVN.
3. AVN found at junction of atria and ventricles at base of atria.
   5.Impulses from AVN spread through ventricies.
4. (Cause contraction of ventricles/ventricular systole
5. (This is followed by)
6. relaxation/resting/diastolic phase/diastole

Question 9

Discuss the causes, development and associated health problems of atherosclerosis.

Answer 9

Causes
Too much fat/cholesterol in the diet/blood. (1)
High LDL levels/low HDL levels or
High LDL:HDL or Low HDL:LDL.
Lack of exercise/inactive lifestyle.(1)
Genetic condition/familial hypercholesterolaemia/FH. (1)
Diabetes/ high blood glucose levels.(1)

Development
There is an accumulation of fatty/ fibrous material/ cholesterol/calcium.(1)
The atheroma/plaque forms beneath the endothelium of an artery.(1)
Artery (wall) thickens/ lumen narrows.(1)
Blood flow is reduced/ restricted/prevented.(1)
Loss of elasticity in artery (wall)/hardening of the artenes occurs.(1)

Health Problems
Raises blood pressure/causes hypertension.(1)
Causes CHD/angina/ heart attack/stroke/PVD (any 2). (1)
Description of CHD/angina/ heart attack/stroke/PVD.(1)

Question 10

Discuss the diagnosis, treatment and role of insulin in Type 1 and Type 2
diabetes.

Answer 10

Diagnosis
Glucose presence in urine suggests diabetes.(1)
(Diagnosis made by carrying out a glucose tolerance test (1)
Individual fasts/does not eat prior to the test.(1)
Individual drinks a glucose solution/drink.(1)
Blood glucose concentration that remains high indicates diabetes. (1)
Type 1 diabetes tends to be diagnosed in children while type 2 diabetes tends to be diagnosed in adults/later in life.(1)

Treatment
Type 1 diabetes is treated with regular doses/ injections of insulin.(1)
Type 2 diabetes is treated/controlled by lifestyle changes/weight loss/exercise/ dietary changes.(1)

Role of Insulin
Insulin is produced in the pancreas.(1)
Type 1 diabetics are unable to produce insulin.(1)
Insulin converts glucose into glycogen.(1)
Type 2 diabetics can produce insulin but cells are less sensitive/ resistant to it.(1)
In Type 2 diabetics there are less insulin receptors on cells.(1)

Question 11

Give an account of hormonal control of puberty and sperm production in
males.

Answer 11

1. At puberty a (releaser) hormone is produced by the hypothalamus.
2. The pituitary gland releases follicle stimulating hormone/ FSH and interstitial cell stimulating hormone /ICSH.
3. FSH/ICSH acts on/targets the testes
4. FSH stimulates sperm production in the seminiferous tubules.
5. ICSH stimulates the production of testosterone in the interstitial cells.
6. Testosterone stimulates sperm production
   7.Sperm/gametes are produced from germline cells by meiosis.
7. Testosterone activates the prostate gland/seminal vesicles.
8. Secretions affect/maintain sperm mobility/viability or named
   example
9. Negative feedback control / feedback inhibition of sperm / testosterone production exists.
10. High levels of testosterone inhibits /reduces/controls FSH/ICSH production.

Question 12

Give an account of treatments for male and female infertility.

Answer 12

1. Drug treatment / fertility drugs are used to stimulate/trigger ovulation/super ovulation.
2. (Some) drugs prevent the negative feedback of ostrogen on FSH production.
3. Other drugs mimic the effect of FSH/LH.
4. Artificial Insemination is used if a man has a low sperm count
5. (Several) sperm/semen samples are collected.
   OR
6. Sperm can be provided bv a donor. sperm semen is inserted into the female reproductive tract by means other than sexual
   7.intercourse / syringe.Intra-cytoplasmic sperm injection/ GS is used when man has a low sperm count/when sperm are defective.
7. The head of the sperm is (directly) injected/inserted into the egg.
8. During In vitro fertilisation/IVF eggs are fertilised outside the body.
9. Zygotes/fertilised eggs are
   OR
   Blastocysts/ balls of cells/ embryos are transferred into the uterus/womb.
10. Pre-implantation genetic diagnosis / PGD identifies genetic disorders/ chromosome abnormalities .

Question 13

Discuss how cardiovascular disease occurs.

Answer 13

1 (Results of) cardiovascular disease include angina/stroke/heart attack/hypertension or high blood pressure/peripheral vascular disease.
Any 2 mentioned
2 Atherosclerosis is build-up of cholesterol/calcium/fatty/fibrous material in an artery.
3 Low density lipoproteins/LDLs transport cholesterol to the arteries.
4 An atheroma/plaque forms beneath the endothelium/lining of artery.
5 Artery thickens/hardens/loses elasticity/narrows.
6 Blood pressure increases / hypertension develops.
7 Atheroma can rupture and clotting factors are released.
8 Formation of a clot / thrombus occurs or thrombosis occurs.
9The clot/thrombus can break loose forming an embolus.
10 This can block arteries (causing a stroke/heart attack).
11Cells are deprived of oxygen.
12 A deep vein thrombosis (can occur) or DVT is a clot in a vein.
13 High blood glucose levels/diabetes can cause cardiovascular disease.

Question 14

Discuss the screening and testing procedures which may be carried out as part of antenatal care.

Answer 14

1. Mother’s blood pressure / blood type / blood tests / urine tests / general
   health check
   (any 2 named)
   2.Ultrasound (imaging / scan)
2. Dating scan / scan at 8-14 weeks is used to determine stage of pregnancy / due date
   4.Anomaly scan / scan at 18-20 weeks for serious physical problems
3. Biochemical / chemical tests detect (physiological) changes of pregnancy
   6.Marker chemicals / named chemical can indicate medical conditions / can give a false positive result
   7.Diagnostic / further testing can follow from routine testing / named test
4. Amniocentesis / cells from amniotic fluid used to produce karyotype / to test for Down’s Syndrome / chromosome abnormalities
5. Chorionic villus sampling / CVS - cells from placenta / chorion used to produce karyotype / to test for Down’s syndrome / chromosome abnormalities
6. If both amniocentesis and CVS named but no description given so not getting 8 or 9
   11.CVS carried out earlier in pregnancy than amniocentesis
7. Allows immediate karyotyping
8. CVS has higher risk of miscarriage

Question 15

Discuss the exchange of substances between plasma and body cells.

Answer 15

1.Plasma is the liquid part of the blood
2.(Any 3) named dissolved substances carried - oxygen, carbon dioxide, glucose, amino acids, urea, vitamins, minerals, etc
3. Site of exchange is at the capillaries
4. Capillaries have a large surface area / thin walls / narrow diameter
5.High pressure (at the arterial end) forces fluid/plasma out of capillaries / pressure filtration
6.Tissue fluid (that bathes the cells)
7.Plasma proteins / blood cells do not pass through capillary walls / stay in blood
8. (Dissolved) substances diffuse / move from tissue fluid into body cells
9. Waste products / named example diffuse / move out of the cells
10. To be excreted / carbon dioxide breathed out
11. Liquid / water / tissue fluid returns into the plasma / blood
12. (Excess) tissue fluid enters lymphatic vessels/lymph
13. This lymph/ fluid is carried back to the blood (by lymphatic system ).

Question 16

Give an account of the nervous system under the following headings:
(i) the role of neurotransmitters at the synapse;
(in) converging and diverging neural pathways.

Answer 16

(i)the role of neurotransmitters at the synapse

1. The synapse/synaptic cleft is the junction/ gap between neurones/nerve cells
2. Neurotransmitters are stored in /released from vesicles*
3. Neurotransmitters are released on arrival of impulse
4. Neurotransmitters diffuse across the cleft
5. Neurotransmitters bind with/reach receptors*
6. A threshold/minimum number of neurotransmitters is needed (for the impulse to continue)
7. Noradrenaline is removed by reabsorption
8. Acetylcholine is broken down by enzymes / acetylcholinesterase
   Only award points 9 or 10 if neither of points 7 and 8 have been awarded
   9.Both noradrenaline and acetylcholine named but no/wrong description of their removal given
9. Both forms of neurotransmitter removal given but no/wrong mention of
   noradrenaline and acetylcholine

(il) converging and diverging neural pathways
11. A converging pathway has several neurones linking to one neurone (if diagram must show direction of impulse)*
12. This increases the neurotransmitter concentration/chances of impulse
generation
13. Any example of a converging pathway, eg rods of retina
14. A diverging pathway has one neurone linking to several neurones (if diagram must show direction of impulse)*
15. This means that impulses are sent to several destinations at the same time
16. Any example of a diverging pathway, eg fine motor control in fingers or release of sweat from sweat glands

Question 17

Give an account of the nervous system under the following headings:
(i) the role of neurotransmitters at the synapse;
(in) the structure and function of neural pathways.

Answer 17

the role of neurotransmitters at the synapse
1. The synapse / synaptic cleft is the junction / gap between neurones / nerve cells*
2. Neurotransmitters are stored in/ released from vesicles*
3. Neurotransmitters are released on arrival of impulse
4. Neurotransmitters diffuse across the gap
5. Neurotransmitters bind with/reach receptors*
6. A threshold / minimum number of neurotransmitters is needed (for the impulse to continue)
7.Neurotransmitters are removed by enzymes and reuptake / reabsorption
8.Neurotransmitters must be removed to prevent continuous stimulation
9.Two named neurotransmitters - acetylcholine, noradrenaline, dopamine, endorphins.

(il) the structure and function of neural pathways
10. A converging pathway has several neurones linked to one neurone (if diagram must show direction of impulse)*
11. This increases the neurotransmitter concentration / chances of impulse generation / sensitivity to excitory or inhibitory signals
12. A diverging pathway has one neurone linked to several neurones (if diagram must show direction of impulse)*
13. This means that impulses are sent to/influence several destinations at the same time
14. Reverberating pathways - neurones later in pathway synapse/link with neurones earlier in the pathway
15. New neural pathways can bypass areas of brain damage / create new responses / suppress reflexes / create plasticity
16. Converging, diverging and reverberating pathways all named but no correct description.

Question 18

Describe how recreational drugs can affect the brain.

Answer 18

Describe how recreational drugs can affect the brain
1. Many affect (neurotransmission in) the reward circuit of the brain
2. They alter mood / cognition/ perception/ behaviour (any two)
3. They may stimulate the release of neurotransmitters
4. They may act as agonists or antagonists (both)
5. Agonists imitate the actions of neurotransmitters
6. Antagonists prevent the binding of neurotransmitters / bind to receptors
Awarded if agonists and antagonists not named but both functions given correctly.
7. Drugs may inhibit the reuptake / enzyme degradation of neurotransmitters (at a synapse)
8. Sensitisation may occur with an increase in the number/sensitivity of receptors
9. Antagonists cause sensitisation leading to addiction
10. Desensitisation may occur with a decrease in the number/sensitivity of receptors
11. Agonists cause desensitisation leading to drug tolerance

Question 19

Describe how recreational drugs can affect the brain.

Answer 19

Describe how recreational drugs can affect the brain
1. Many affect (neurotransmission in) the reward circuit of the brain
2. They alter mood / cognition/ perception/ behaviour (any two)
3. They may stimulate the release of neurotransmitters
4. They may act as agonists or antagonists (both)
5. Agonists imitate the actions of neurotransmitters
6. Antagonists prevent the binding of neurotransmitters / bind to receptors
Awarded if agonists and antagonists not named but both functions given correctly.
7. Drugs may inhibit the reuptake / enzyme degradation of neurotransmitters (at a synapse)
8. Sensitisation may occur with an increase in the number/sensitivity of receptors
9. Antagonists cause sensitisation leading to addiction
10. Desensitisation may occur with a decrease in the number/sensitivity of receptors
11. Agonists cause desensitisation leading to drug tolerance

Question 20

Give an account of the nervous system under the following headings:
(i) the somatic nervous system;
(ii)the autonomic nervous system.

Answer 20

(iii) The somatic nervous system (SNS)
1. ‘The somatic nervous system controls the body’s skeletal muscles.
2. It controls (mainly) voluntary actions.
3. Sensory neurones (of the SNS) carry impulses into the CNS / brain from the
senses.
4. Motor neurones (of the SNS) carry impulses out of the CNS / brain to muscles.
5. SNS does control some reflex actions.

(iv) ‘The autonomic nervous system (ANS)
6.The ANS works automatically / without conscious control.
7. Impulses originate in the medulla (region of the brain)
8. It is made up of the sympathetic and parasympathetic systems.
9. These two systems are antagonistic in action.
10. ‘The sympathetic system prepares the body for fight or flight.
11. ‘The parasympathetic system prepares the body for rest and digest.
12. Correct description of the effect of the ANS in controlling heart rate.
13. Correct description of the effect of the ANS in controlling breathing rate.
14. Correct description of the effect of the ANS in controlling peristalsis.
15. Correct description of the effect of the ANS in controlling intestinal secretions.

Question 21

Describe the function and mechanism of neurotransmitter action at the synapse.

Answer 21

1. Neurotransmitters relay messages from nerve to nerve / muscle
2. Gap between them is called the synaptic cleft
3. Neurotransmitters are stored in vesicles
4. Arrival of an impulse causes vesicles to fuse with membrane and release neurotransmitter
5. Neurotransmitters diffuse across the cleft
6. Neurotransmitters bind to receptors
7. Receptors determine whether the signal is excitory or inhibitory
8. Neurotransmitters are removed by enzymes / re-uptake
9. Removal prevents continuous stimulation of post-synaptic neurones
   10.Summation of weak stimuli can release enough neurotransmitter to fire an impulse

Question 22

Discuss the encoding, storage and retrieval of information in memory.

Answer 22

Encoding
1. Encoding is transferring information into memory/short-term memory (STM)/ long-term memory (LTM).
2. Transfer occurs from sensory memory to
STM to LTM.
3. Only selected images/sounds are encoded/transferred into
STM/transferred from sensory memory.
4. Information is transferred from STM to long-term memory (LTM) by rehearsal/ organisation/elaboration.
Any 2 for the mark
5. Rehearsal is the repeating of information/organisation involves putting information into related groups/ elaboration involves adding meaning to information.
6. Rehearsal is a shallow form of encoding/elaboration is a deeper form of encoding (information into LTM).

Storage
7. Sensory memory retains /holds information for a few seconds.
8. STM has a limited (storage) capacity/ holds information for a short time.
9. The number of items held in STM can be increased by chunking.
10. Information is retained in STM by rehearsal.
11. Information is lost from STM by displacement/decay.
12. LTM has an unlimited (storage) capacity/holds information for a long time.

Retrieval
a. Retrieval of information (from LTM) is aided/helped by the use of contextual cues.
b.Contextual cues relate to the time/ place where the information was (firstly) encoded/memory was created.

Question 23

Describe vaccination and discuss its role in establishing herd immunity in a population.

Answer 23

Vaccination
1. Vaccination develops/provides immunity against a pathogen/ disease.
OR
Vaccination produces memory cells against a pathogen.
2. Antigens from pathogens are used to create memory cells /immunological memory.
3. If a vaccinated individual becomes infected/exposed again, antibody production/the immune/the secondary response is greater /more rapid/ prevents symptoms developing.
4. Vaccines can contain inactivated (pathogen) toxins/ dead pathogens/ parts of pathogens/weakened pathogens.
5. Antigens are usually mixed with an adjuvant
OR
Vaccines usually contain/are mixed with an adjuvant.
6. An adjuvant makes the vaccine more effective/enhances the immune

Herd Immunity
a. Mass vaccination programmes are designed to establish herd immunity (to a disease).
b. Herd immunity occurs when a large percentage/high numbers of a population are immune/immunised/ vaccinated.
c. Herd immunity reduces the spread of diseases.
d. Herd immunity protects non-immune individuals as they have a lower probability/less chance of coming into contact with infected individuals.
e. Diseases have a threshold for herd immunity.
f. The threshold depends on the type of disease/the effectiveness of the vaccine/the density of the population.
Any 2 for the mark
g. Herd immunity/vaccination may not be possible due to poverty.
h. Herd immunity/ vaccination may not occur due to vaccine rejection.

Question 24

Describe the contents of vaccines and the design of clinical trials used to establish their effectiveness.

Answer 24

a. Vaccines contain antigens from (infectious) pathogens.
b. Vaccines contain inactivated pathogen toxins/ dead pathogens/parts of pathogens/ weakened pathogens.
c. (These are usually) mixed with/contain an adjuvant.
d. An adjuvant makes the vaccine more effective/enhances the immune response

1. Clinical trials are used to make sure vaccines/ drug are safe.
2. Subjects/individuals are divided /placed into groups in a randomised way.
3. Characteristics/age/gender are controlled/similar.
4. (In a clinical trial) one group/some people receives the vaccine/ drug while the second group/some people receive a placebo.
5. Using a placebo ensures valid comparisons/results.
6. In a double-blind trial neither the subjects/participants nor the researchers/doctors know which group subjects are in /treatment is given.
7. Bias is prevented / reduced through randomised allocation/ double-blind (trial) (to increase validity).
8. Groups must be of a suitable/ large size to reduce experimental error/increase reliability.
9. The results are compared to determine any (statistically) significant differences