P1 Weak points

Question 1

explain how respiration causes a fall in blood PH.
mention a key enzyme in the process
(4)

Answer 1

• respiration produces carbon dioxide
• carbon dioxide reacts with water t produce carbonic acid
• carbonic acid dissociates to release hydrogen and hydrogen carbonate ions
  carbonic anhydrase catalyses the dissociation of carbonic acid

Question 2

explain how urea is produced in the body (2)

Answer 2

• proteins in the body are deaminated, producing ammonia
• ammonia combines with carbon dioxide to produce urea, which can then be excreted from the body

Question 3

explain how increased sweating is involved in the regulation of body temperature (2)

Answer 3

heat energy is used to break the hydrogen bonds between water, creating water vapour.
therefore evaporation of water vapour off skin surface cools the body, regulating body temperature

Question 4

explain the importance of acetylcholinsterase at the neuromuscular junction

Answer 4

acetylcholinsterase breaks down acetyl choline so that no further action potentials are triggered on the post synaptic membrane
- if it was not present, acetyl choline would not be broken down which would lead to permanent contraction: possibly paralysis.

Question 5

state and explain the 2 types of summation needed to know in biology (not PE!!)

Answer 5

spatial summation: several impulses, but impulses are fired at different areas of the neurone

temporal summation: multiple action potentials carried along one neurone, one after the other