AS PAPER 2 2020

Question 1

Give 2 ways in which the student could ensure his samples would provide a measure of the variation between individuals in each population. [2 marks]

Answer 1

Select at random
Large sample

Question 2

What can you conclude from the appearance of valves about heart muscle activity and blood movement between: ventricles and arteries (valves are closed)
atria and ventricles (valves are open)

Answer 2

ventricles and arteries:
ventricle is relaxed
no blood movement in arteries.

atria and ventricles:
atria is contracted
blood movement from atria to ventricles

Question 3

which blood vessel carries blood at the lowest blood pressure?

Answer 3

vena cava

Question 4

what can you conclude about the damage caused to beetroot cells by water, ethanol, hydrochloric acid (all at 25) and different temperatures (70)? [4 marks]

Answer 4

water at 25 caused no damage
ethanol and acid caused some damage to cell surface membrane
70 caused the most damage
ethanol dissolves phospholipid bilayer
acid changes shape of carrier/ channel protein
at 70, the protein is denatured
permeability of membrane is increased

Question 5

assuming the scientists are correct, suggest how eating stale bread could help to reduce weight gain. [3 marks]

Answer 5

less hydrolysis of starch
to maltose
less absorption of glucose

Question 6

explain how HIV affects the production of antibodies when AIDS develops in a person. [3 marks]

Answer 6

less antibody produced
HIV destroys T helper cells
less B cells activated

Question 7

phloem pressure is reduced during the hottest part of the day. use your understanding of transpiration and mass flow to explain why. [3 marks]

Answer 7

high rate of transpiration
water lost through stomata
this causes less water movement from xylem to phloem

Question 8

describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. [5 marks]

Answer 8

micelles contain bile salts, FA and MG
they bring FA and MG to the lining of the ileum so a higher conc of FA and MG is maintained
FA and MG are absorbed by diffusion
triglycerides are reformed
vesicles are moved to cell membrane.

Question 9

Describe how the structure of a protein depends on the amino acids it contains. [5 marks]

Answer 9

structure is determined by position of R groups
Primary structure is order of AA
Secondary structure formed by H bonds between AA
Tertiary structure formed by interactions between R groups
Creates AS in enzymes
Quaternary structure formed by more than one polypeptide bonded together