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Question 1

Describe how a phagocyte destroys a pathogen present in the blood.

Answer 1

(a) 1.

Engulfs;

Accept endocytosis

OR

Description

Ignore taken in’

2.

Forming vesicle/phagosome and fuses with lysosome;

3. Enzymes digest/hydrolyse;

Question 2

Mucus produced by epithelial cells in the human gas exchange system contains triglycerides and phospholipids.

Compare and contrast the structure and properties of triglycerides and phospholipids.

Answer 2

1. Both contain ester bonds (between glycerol and fatty acid); All statements must be clearly comparative or linked by the candidate, not inferred from separate statements. Accept mark points shown on adjacent annotated diagrams.
2. Both contain glycerol;
3. Fatty acids on both may be saturated or unsaturated;
4. Both are insoluble in water;
5. Both contain C, H and O but phospholipids also contain P; Must relate to element.
6. Triglyceride has three fatty acids and phospholipid has two fatty acids plusphosphate group;
7. Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region;

Accept ‘non-polar’ for hydrophobic and ‘polar’ for hydrophilic.

8. Phospholipids form monolayer (on surface)/micelle/bilayer (in water) but triglycerides don’t;

Question 3

Describe the role of DNA polymerase in the semi-conservative replication of

Answer 3

1. Joins (adjacent DNA) nucleotides;

2(Catalyses) condensation (reactions):

3. (Catalyses formation of) phosphodiester bonds (between adjacent nucleotides).

Question 4

Eukaryotic cells produce and release proteins.

Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells

Do not include details of transcription and translation in your answer.

Answer 4

1. DNA in Is code (for protein),
2. Ribosomes/rough endoplasmic reticulum produce (protein), Accept rER for ‘rough endoplasmic reticulum
3. 4. Mitochondria produce ATP (for protein synthesis), Golgi apparatus package/modity:

OR

Carbohydrate added/glycoprotein produced by Golgi apparatus, Accept body for ‘apparatus’

5. Vesicles transport

transports;

6. (Vesicles) fuse with cell(-surface) membrane; Accept exocytosis at cell membrane

Question 5

Describe the role of micelles in the absorption of fats into the cells lining the ileum.

Answer 5

1. Micelles include bile salts and fatty acids;
2. Make the fatty acids (more) soluble in water;
3. Bring fatty acids to lining (of the ileum);
4. Maintain high(er) concentration of fatty acids to cell lining (of the ileum):
5. Fatty acids (absorbed) by diffusion

Question 6

Describe the gross structure of the human gas exchange system and how we breathe in and out.

Answer 6

1. Named structures-trachea, bronchi, bronchioles, alveoli; Reject mp1 structures from other physiological systems are named but award mp2 If the correct structures are in the correct ordor.

2.

Above structures named in correct order OR Above structures labelled in correct positions on a diagram,

Reject mp1 if structures from other physiological systems are

named but award mp2 if the correct structures are in the

correct order.

3. 4. Breathing in-diaphragm contracts and external intercostal muscles contract; (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric, resulting in air moving in);

For thoracic cavity accept ‘lungs’ or ‘thorax’.

Reference to thoracic cavity only required once.

5. Breathing out-Diaphragm relaxes and internal intercostal muscles contract; Accept diaphragm relaxes and (external) intercostal muscles relax and lung tissue elastic (so recoils).

6.

(Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric, resulting in air moving out);

For thoracic cavity accept ‘lungs’ or ‘thorax. Reference to thoracic cavity’ only required once.