ATP

Question 1

Describe the structure of ATP

Answer 1

• Adenine (nitrogen organic base)
• Ribose sugar
• Phosphates: a chain of THREE phosphate groups.

Question 2

What type of molecule is ATP?

Answer 2

phosphorylated macromolecule

Question 3

What does ATP stand for?

Answer 3

Adenosine triphosphate

Question 4

Why is it a key feature that ATP has THREE phosphate groups?

What does it help with?

Answer 4

• key to how ATP STORES energy
• bonds between the phosphate groups are unstable = low activation energy = easily broken.
• When they do break, releases a considerable amount of energy.

Question 5

In living cells, what phosphate is removed when ATP releases energy?

Answer 5

ONLY the TERMINAL phosphate
is removed

Question 6

Water is used to convert ATP to ADP.

What is this reaction considered as?

What enzyme catalyses this reaction?

Is it reversible or irreversible?

Answer 6

Hydrolysis reaction.

Catalysed by the enzyme ATP HYDROLASE (ATPase).

Reversible

Question 7

Conversion of ATP —> ADP is a reversible reaction.

So how can ADP —-> ATP?

What enzyme is this reaction catalysed by?

Water is removed in this reaction. What type of reaction is this considered as?

Answer 7

• energy added to an inorganic phosphate

to ADP to re-form ATP

Catalysed by ATP synthase.

A condensation reaction

Question 8

The synthesis of ATP —> ADP involves the addition of a phosphate molecule to ADP.

What are the 3 ways it occurs?

Answer 8

-in chlorophyll-containing plant cells during photosynthesis (photophosphorylation)

• in plant and animal cells during respiration (oxidative phosphorylation)
• in plant and animal cells when phosphate groups are transferred from donor molecules to ADP (substrate-level phosphorylation).

Question 9

ATP is an IMMEDIATE energy source.

What are the reasons that ATP is considered as this?

Answer 9

1. Energy released: ATP molecule < glucose molecule.

Energy for reactions released = smaller, in more manageable quantities.

2. Hydrolysis of ATP to ADP = single reaction = immediate energy released.

Breakdown of glucose is a long series of reactions = energy release takes longer.

Question 10

ATP cannot be stored.

So how do cells that require ATP get it?

What organelle do they have an abundance of for this?

Give 2 examples of cells that requires a lot of ATP.

Answer 10

It is continuously made within the mitochondria of cells that need it.

Ex:

muscle fibres + epithelium of the small intestine, requires energy for movement and active transport respectively, possess many large mitochondria.

Question 11

How is ATP used in energy-requiring processes in cells?

(5 ways)

Answer 11

• Metabolic processes.
• Movement
• Active transport.
• Secretion.
• Activation of molecules.

Question 12

Explain how ATP is used in metabolic processes in cells.

Answer 12

ATP provides the energy needed to build up macromolecules from their basic units.

Eg. making starch from glucose / polypeptides from amino acids.

Question 13

Explain how ATP is used for movement.

Answer 13

-Provides energy for muscle contraction.

In muscle contraction, ATP provides the energy for the filaments of muscle to slide past one another and therefore shorten the overall length of a muscle fibre.

Question 14

Explain how ATP is used in active transport in cells (membranes)

Answer 14

ATP provides the energy to change the shape of carrier proteins in plasma membranes.

This allows molecules or ions to be moved against a concentration gradient.

Question 15

Explain how ATP is used for secretion in cells.

Answer 15

ATP is NEEDED to form the lysosomes necessary for the secretion of cell products.

Question 16

Explain how ATP is used for secretion in cells.

Answer 16

The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds in order to make them more reactive, lowering the activation energy in enzyme-catalysed reactions.

Eg. The addition of phosphate to glucose molecules at the start of glycolysis.