paper 3 2023

Question 1

Describe how stimulation of a Pacinian corpuscle produces a generator potential

Answer 1

pressure pushes on the lamellae and deforms the membrane.
stretch-mediated sodium channels in the membrane open
sodium ions diffuse into neurone, depolarising it and creating a generator potenital

Question 2

Use Figure 1 to describe what is meant by the all-or-nothing principle

Answer 2

high pressure stimulus causes action potential to be generated when threshold is reached

Question 3

A student investigated the effect of different sugars on the rate of respiration in yeast.
Yeast normally respires glucose.
, suggest two variables the student needed to keep constant
in her investigation.

Answer 3

• concentration of glucose
  -type of yeast
  -volume of yeast

Question 4

The student repeated the experiment using yeast in maltose solution. She found the
rate of carbon dioxide production was slower than with yeast in glucose solution.
Suggest why.

Answer 4

maltose is a disaccharide whereas glucose is a monosaccharide so bonds are stronger

Question 5

link reaction

Answer 5

pyruvate —-co2–>acetate—-coA—>acetyl coA