Cells- Topic 4- Metabolism

Question 1

How does the structure of the internal membranes of the chloroplast facilitate chemical processes?

Answer 1

The highly folded membrane provides a large surface area which increases the rate of the absorption of light, as the stacks of membranous thylakoids increase the rate of attachment of photosynthetic pigments like chlorophyll.

Question 2

How does the structure of the internal membranes of the mitochondria facilitate chemical processes?

Answer 2

The folded inner membrane provides a very large surface area and increases the rate of the synthesis of ATP in aerobic respiration.
The external surface area to volume ratio of a mitochondrion is greater than that of its cells surface area to volume ratio as when size decreases, surface area to volume ratio increases, and mitochondria are much smaller in size.

Question 3

Why is it advantageous for cellular respiration to occur in a series of small, stepwise reactions rather than a single large reaction?

Answer 3

1. Small steps provide intermediate compounds that can be used as starting points for other reactions.
2. Small steps mean less energy is released, which is easier to capture as ATP rather than being lost as heat.
3. Large reactions would produce unfavourable conditions for enzymes, such a change in pH or an increase in temperature. Small steps control the release of heat and change in pH, maintaining favourable conditions.

Question 4

Why are specific enzymes required at each step in a metabolic pathway?

Answer 4

Enzymes have an active site with a shape that is complementary to the substrates. Other enzymes have a different shape that cannot bind. As such, a specific enzyme is required at each step.

In a metabolic pathway, if an enzyme is inhibited it causes the substrate before to decrease in concentration and the substrate after to decrease in concentration.