21: Respiration - Problems

Question 1

The electron micrograph below shows the cross section of a mitochondrion.

Name structures X and Y. (2)

Answer 1

X: crista
Y: outer mitochondrial membrane

Question 2

The electron micrograph below shows the cross section of a mitochondrion.

Mitochondria in animal cells can vary greatly in length and shape. However, their diameter is usually within 1μm. Suggest one advantage of having their diameter within 1μm. (1)

Answer 2

A smaller diameter decreases the diffusion distance. This allows molecules to diffuse rapidly into the centre of mitochondria.

Question 3

The electron micrograph below shows the cross section of a mitochondrion.

The ratio of the surface area of structure X to the surface area of structure Y from the muscle cells of mice P and Q were calculated. The ratio in mouse Q is higher than that in P.

Deduce which mouse is more likely to have carried out physical exercise for a longer period time and explain. (4)

Answer 3

Mouse Q.
The ratio of the surface area of structure X to the surface area of structure Y in mouse Q is higher. This indicates that the mitochondria in mouse Q contains more structure X.
Structure X is packed with enzymes involved in the reactions of respiration.
Mitochondria with more structure X can produce more ATP for muscle contraction during physical exercise.