june 2017 paper 3

Question 1

Use your knowledge of how myosin and actin interact to suggest how the myosin
molecule moves the mitochondrion towards the presynaptic membrane.

Do not include the roles of calcium ions and tropomyosin in your answer. (2)

Answer 1

myosin head attaches to actin and performs power stroke
this pulls mitochondria along the actin
next myosin head attaches to actin

Question 2

use the data to evalaute the use of artifical fertilisers on grain producing crops in india (2)

Answer 2

using more but getting less response over time
less cost effective over time

Question 3

Outline a method the ecologists could have used to determine the plant species
richness at one site (3)

Answer 3

-selecting sites at random e.g. use a random number generator
-place large number of quadrats at coordinates
identify species

Question 4

The student wanted to determine the rate of water loss per mm2 of surface area of
the leaves of the shoot in Figure 5.

Outline a method she could have used to find this rate. You should assume that all
water loss from the shoot is from the leaves.

Answer 4

-draw around leaf on graph paper and count number of squares
-on either side
-divide rate by suface area

Question 4

Sometimes, a mutagenic agent causes DNA to break. A different enzyme called
ATM binds to the broken DNA. This leads to the activation of a protein coded for by
a tumour suppressor gene. The effect of ATM binding is to stop cell division until
DNA is repaired.

A mutation could result in a person having non-functional forms of the gene that
produces ATM.

What can you predict about the possible effects of having a non-functional form of
ATM? (3)

Answer 4

-ATM will not bind to DNA
-DNA not repaired
-cell divison continues