97 WJEC Biology AS Level - Marianne Izen - 2nd Edition (Nucleic Acids And Their Functions)

Question 1

What are the advantages in having ATP as an intermediate in providing energy, compared with using glucose directly?

Answer 1

1. The hydrolysis of ATP to ADP involves a single reaction that releases energy immediately, whereas the breakdown of glucose involves many intermediates and it takes longer for energy to be released.
2. Only one enzyme is needed to release energy from ATP, but many are needed to release energy from glucose.
3. ATP releases energy in small amounts, when and where it is needed, but glucose contains large amounts of energy, which would be released all at once.
4. ATP provides a common source of energy for many different chemical reactions, increasing efficiency and control by the cell.

Question 2

Describe the roles that ATP plays in the body?

Answer 2

ATP provides the necessary energy for cellular activity:

1. Metabolic processes - to build large, complex molecules from smaller, simpler molecules, such as DNA synthesis from nucleotides, proteins from amino acids.
2. Active transport- to change the shape of carrier proteins in membranes and allow molecules or ions to be moved against a concentration gradient.
3. Movement - for muscle contraction, cytokinesis.
4. Nerve transmission - sodium-potassium pumps actively transport sodium and potassium ions across the axon membrane.
5. Secretion - the packaging and transport of secretory products into vesicles in cells.

Question 3

Calculate the number of ATP molecules in the body

Answer 3

Question 4

Calculate the number of ATP recycling events

Answer 4

Question 5

Calculate the number of reactions based on 10000 recycling events a day

Answer 5

Question 6

What happens to the recipient molecule when a phosphate group is transferred from ATP to it?

Answer 6

When a phosphate group is transferred from ATP to another molecule, it makes the recipient molecule more reactive, lowering the activation energy of a reaction involving that molecule.

Question 7

Is ATP a source of energy?

Answer 7

ATP is an immediate source of energy in the cell.

Cells do not store large quantities, for example a resting human has about 5 g of ATP, a few seconds’ supply.

Question 8

Can ATP be stored in large quantities?
What are the implications of this?

Answer 8

ATP cannot be stored in large quantities and must be made continuously.

Cells generating movement or performing active transport contain many mitochondria, where ATP is synthesised.

Question 9

Answer 9