1. Biological Molecules - ATP

Question 1

What are the 3 components of an ATP molecule?

Answer 1

• Adenine
• Ribose
• Phosphates

Question 2

What is ribose? What is its function in the structure of ATP?

Answer 2

A sugar molecule with a 5-carbon ring structure (pentose sugar) that acts as a backbone to which the other parts are attached.

Question 3

Describe the bonds between the phosphate groups:

Answer 3

They are unstable and so have a low activation energy, which means they are easily broken.

Question 4

What is the chemical equation for the hydrolosis of ATP?

Answer 4

ATP (adenine triphosphate) + H2O -> ADP (adenine diphosphate) + Pi (inorganic phosphate) + E (energy)

Question 5

What enzyme catalyses the hydrolosis of ATP to ADP?

Answer 5

ATP hydrolase (ATPase)

Question 6

What is the reverse reaction of ATP to ADP catalysed by?

Answer 6

ATP synthase.

Question 7

What type of reaction is the reverse reaction?

Answer 7

A condensation reaction, as water is produced.

Question 8

The synthesis of ATP from ADP involves the addition of a phosphate molecule to ADP, it occurs in which 3 ways?

Answer 8

• Photophosphorylation (in chlorophyll-containing plant cells during photosynthesis)
• Oxidative phosphorylation (in plant and animal cells during respiration)
• Substrate-level phosphorylation (in plant and animal cells when phosphate groups are transferred from donor molecules to ADP)

Question 9

What type of energy source is ATP for a cell?

Answer 9

In immediate energy source.

Question 10

Give 2 reasons why ATP is a better immediate energy source than glucose:

Answer 10

• Each ATP molecule releases less energy than each glucose molecule. The energy is therefore released in smaller, more manageable quantities with ATP, compared to the greater, less manageable release of energy from a glucose molecule
• The hydrolosis of ATP to ADP is a single reaction that releases immediate energy. The breakdown of glucose is a long series of reactions that takes longer to release energy

Question 11

Why might some cells possess many large mitochondria in regards to ATP?

Answer 11

As ATP cannot be stored, it has to be continuously made within the mitochondria. Cells that require energy for movement and active transport respectively therefore have many mitochondria to produce enough ATP.

Question 12

Give 5 energy-requiring processes in cells that ATP is used in:

Answer 12

• Metabolic processes
• Movement
• Active transport
• Secretion - needed to form lysosomes necessary for secretion of cell products
• Activation of molecules - the inorganic phosphate produced can be used to phosphorylate other compounds in order to make them more reactive, thus lowering the activation energy in enzyme-catalysed reactions