Topic 1B- More Biological Molecules (ATP)

Question 1

What is the energy released from glucose used to make?

What three things is adenosine triphosphate made from?

What is ATP known as and why?

What happens once ATP is made?

How is the energy in ATP stored?

How is this energy released from ATP?

What happens to ATP when energy is needed by a cell?

What type of reaction is this?

What happens to a phosphate bond and what is then released?

What is this reaction catalysed by?

Answer 1

ATP (adenosine triphosphate)

The nucleotide base adenine; combined with a ribose sugar and three phosphate groups

A nucleotide derivative because it’s a modified form of a nucleotide

ATP diffuses to the part of the cell that needs energy

The energy in ATP is stored in high energy bonds between the phosphate groups

Released via hydrolysis reaction

ATP is broken down into ADP (adenosine diphosphate) and Pi (inorganic phosphate)

This is a hydrolysis reaction

A phosphate bond is broken and energy is released

This reaction is catalysed by the enzyme ATP hydrolase.

Question 2

What is the equation for the breakdown of ATP?

What type of reaction is this?

Answer 2

ATP + H2O —> ADP + Pi
(+ATP hydrolase and Energy Released)

A hydrolysis reaction.

Question 3

What can happen to the ATP hydrolysis reaction?

What does this mean?

What can happen to the released inorganic phosphate?

What is this known as?

What does this often do to the compound?

How can ATP be resynthesized (full detail)?

What two reactions does this occur in?

What is this reaction catalysed by?

Answer 3

Can be “coupled” to other energy-requiring reactions in the cell

This means the energy released can be used directly to make the coupled reaction happen, rather than being lost as heat

It can be added to another compound

Known as phosphorylation

This often makes the compound more reactive

ATP can be resynthesized in a condensation reaction between ADP and Pi

This reaction happens during both respiration and photosynthesis

This reaction is catalysed by the enzyme ATP synthase.

Question 4

What is the equation for the synthesis of ATP?

What type of reaction is this?

Answer 4

ADP + Pi —> ATP
(+ATP synthase and Energy used)

A condensation reaction.

Question 5

Exam Question:

Why is ATP a useful source of energy in cells? (4 marks)

Answer 5

1. Each molecule of ATP releases a small amount of energy
2. Energy from ATP is readily available because it is released in a one-step reaction
3. Phosphorylates/adds phosphate makes (phosphorylated substances) more reactive/lowers activation energy for other reactions
4. ATP is not lost from cells because it can be regenerated from ADP and Pi, ATP can be resynthesized rapidly in cells.

Question 6

Describe how and where the following reactions synthesise ATP:

1. Photophosphorylation
2. Oxidative Phosphorylation
3. Substrate-level Phosphorylation

Answer 6

1. In photosynthesis, ATP is produced in a process called photophosphorylation: where light is used to add the inorganic phosphate to ADP
2. In respiration, ATP is produced in a process called oxidative phosphorylation: within mitochondria electrons are transported, releasing energy to add Pi
3. This is when a reaction has occurred, releasing enough energy to combine any nearby Pi and ADP together.