june 2017- paper 1

Question 1

describe the structure of glycogen (2)

Answer 1

large polymer of a-glucose joined together by glycosidic bonds

Question 2

co-transport (3)

Answer 2

• hydrolysis of atp used
• substances bind to the protein
• protein changes shape

Question 3

why does high absorption of salt lead to more tissue fluid (2)

Answer 3

• lower water potential of tissue fluid

- less water returns to capillary by osmosis

Question 4

why do some bacteria excrete extracellular enzymes (2)

Answer 4

• to digest protein

- so the amino acids can be absorbed

Question 5

how does phagocytosis lead to expression of antigens? (3)

Answer 5

• phagosome fuses with lysosome
• virus destroyed by lysosymes
• antigens are displayed on the cell membrane

Question 6

how does presentation of an antigen lead to the secretion of an antibody? (4)

Answer 6

• TH cell binds to the antigen
• stimulates a B cell
• B cell clones
• produces plasma cells

Question 7

3 comparisons of genetic diversity

Answer 7

• mRNA base sequence
• amino acid sequence
• DNA sequence

Question 8

6 ways an insect’s tracheal system is adapted for efficient gas exchange

Answer 8

• tracheoles have thin walls so short diffusion distance
• highly branched so short diffusion distance
• highly branched so large surface area
• tracheae are tubes of air so fast diffusion
• fluid in the end of tracheoles that moves out during exercise so faster diffusion
• body can be moved to maintain concentration gradient