1.6 - ATP, 1.7 - Water + 1.8 - Inorganic ions

Question 1

Describe how an ATP molecule is formed from its component molecules. (3)

Answer 1

• Adenine, ribose/pentose, 3 phosphates
• Condensation (reaction)
• ATP synthase

Question 2

Water is used to hydrolyse ATP. Name the two products of ATP hydrolysis. (1)

Answer 2

• Adenosine diphosphate and (inorganic) phosphate

Question 3

ATP is an energy source used in many cell processes. Give two ways in which ATP is a suitable energy source for cells to use. (2)

Answer 3

• Releases a relatively small amount of energy / little energy lost as heat
• Releases energy instantaneously
• Phosphorylates other compounds, making them more reactive
• Can be rapidly re-synthesised
• Is not lost from / does not leave cells

Question 4

Describe how ATP is resynthesised in cells. (2)

Answer 4

• From ADP and phosphate
• By ATP synthase
• During respiration/photosynthesis

Question 5

Give two ways in which the hydrolysis of ATP is used in cells. (2)

Answer 5

• To provide energy for other reactions/named process
• To add phosphate to other substances and make them more reactive/change their shape

Question 6

Explain five properties that make water important for organisms. (5)

Answer 6

• A metabolite in condensation/ hydrolysis/ photosynthesis/respiration
• A solvent so (metabolic) reactions can occur / A solvent so allowing transport of substances
• High (specific) heat capacity so buffers changes in temperature
• Large latent heat of vaporisation so provides a cooling effect (through evaporation)
• Cohesion (between water molecules) so supports columns of water (in plants)
• Cohesion (between water molecules) so produces surface tension supporting (small) organisms

Question 7

Water and inorganic ions have important biological functions within cells. Give two properties of water that are important in the cytoplasm of cells. For each property of water, explain its importance in the cytoplasm. (4)

Answer 7

• Polar molecule
• Acts as a (universal) solvent
  or
• (Universal) solvent
• (Metabolic) reactions occur faster in solution
  or
• Reactive
• Takes place in hydrolysis / condensation

Question 8

Describe the roles of iron ions, sodium ions, and phosphate ions in cells. (5)

Answer 8

Iron ions:
- Haemoglobin binds/associates with oxygen
- Haemoglobin transports/loads oxygen
Sodium ions:
- Co-transport of glucose/amino acids (into cells)
- (Because) sodium moved out by active transport/Na – K pump
- Creates a sodium concentration/diffusion gradient
- Affects osmosis/water potential
Phosphate ions:
- Affects osmosis/water potential
- Joins nucleotides/in phosphodiester bond/in backbone of DNA/RNA/in nucleotides
- Used in/to produce ATP
- Phosphorylates other compounds (usually) making them more reactive
- Hydrophilic/water soluble part of phospholipid bilayer/membrane