Exam practise

Question 1

Explain how a transplant of bone marrow cells can help to treat medical conditions.

Answer 1

Stems cell in the bone marrow tissue can differentiate into many types of cells.
They will cure diseases where they are needed.

Question 2

Explain how amylase breaks down starch. Answer in terms of the ‘lock and key theory’.

Answer 2

Starch binds to the active site of amylase because they are complementary.
A chemical reaction occurs that produces smaller molecules.

Question 3

Why did the student leave the starch solution and amylase solution for 5 minutes before mixing them?

Answer 3

To make the starch solution and amylase solution the same temperature AS the WATER

Question 4

Explain the results at 5 and 80 degrees. (iodine solution did not become yellow-brown)

Answer 4

iodine is not yellow-brown because the starch has not been broken down.
because at 5 degrees amylase has low kinetic energy, so there are fewer amylase-substrate collisions.
At 80 degrees, the amylase has been denatured, so the starch can no longer fit in, (so the reaction is not catalysed)

Question 5

The student investigated the effect of temperature on amylase activity. Describe how the student could extend the investigation to determine the effect of a different factor on amylase activity.

Answer 5

Keep the temperature constant, but change the PH and test a range of values

Question 6

Explain why enzyme X works best in the stomach. (graph shows that X has optimum PH of 2)

Answer 6

It works best at 2 PH, and the stomach has hydrochloric acid.

Question 7

Why does a red blood cell burst, but a plant cell does not burst?

Answer 7

Water enters the cell by osmosis.
A plant cell has a cell wall which prevents it from bursting, but a red blood cell doesn’t.

Question 8

What is the function of the coarse adjustment knob?

Answer 8

Bring the specimen into focus