3.1.7 ATP

Question 1

The Structure of ATP:

Answer 1

1. Ribose, a molecule of adenine, 3 phosphate groups (Pi).
2. Nucleotide derivative (modified form of nucleotide).
3. The structure of ADP (adenosine diphosphate) is the same as ATP minus a phosphate.

Question 2

Give the basic equation for ATP hydrolysis and name the enzyme involved in this process.

Answer 2

1. ATP → ADP + Pi
2. Catalysed by the enzyme ATP hydrolase.

Question 3

What occurs during ATP hydrolysis and what does this result in?

Answer 3

`1. Bonds between inorganic phosphate groups are high energy bonds so by breaking one of these bonds a small amount of energy is released.
2. Can be coupled to energy requiring reactions within cells, to provide energy for e.g. active transport, protein synthesis.
3. The inorganic phosphate released can be used to phosphorylate other compounds e.g. glucose, often making them more reactive (i.e. lowers activation energy).

Question 4

Give the basic equation for ATP condensation and name the enzyme involved in this process.
When does ATP condensation occur?

Answer 4

1. ADP + Pi 🡪ATP
2. Catalysed by the enzyme ATP synthase.
3. Happens during respiration or photosynthesis

Question 5

Describe the properties of ATP that make it a suitable immediate energy source.

Answer 5

1. ATP releases energy in small, manageable amounts (so no energy wasted).
2. Only one bond is hydrolysed (single reaction) to release energy (which is why energy release is immediate).
3. Cannot leave the cell, cell has a constant energy store.
4. Note: ATP cannot be stored.