Module 1. Biological molecules (set 3)

Question 1

Describe how an **ATP **molecule is formed from its component molecules.
[4 marks]
[7.1 - JUN21] [AS]

Answer 1

1. and 2. adenine, ribose/pentose, three phosphates;;
2. Condensation (reaction);
3. ATP synthase;

Question 2

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 marks]

Answer 2

1. Releases relatively small amount of energy / little energy lost as heat;
2. Releases energy instantaneously;
3. Phosphorylates other compounds, making them more reactive;
4. Can be rapidly re-synthesised;
5. Is not lost from / **does not **leave cells.

Question 3

How can the inorganic phosphate in ATP be used?

Answer 3

• It can be used to phosphorylate other compounds
• This often **increases **the reactivity of these other compounds

Question 4

Give 2 ways the properties of ATP make it a suitable source of energy in biological processes

Answer 4

• It is soluble
• It involves a single reaction
• Energy is released in small amounts

Question 5

Explain why it is necessary to synthesise such a large amount of ATP

Answer 5

• ATP cannot be stored/ It is an immediate source of energy
• ATP only releases small amounts of energy at a time

Question 6

Explain five properties that make water important for organisms.
[5 marks]
[9.1 - JUN21] [AS]

Answer 6

1. A** metabolite in** condensation/hydrolysis/ photosynthesis/respiration;
2. A **solvent so **(metabolic) reactions can occur
   OR
   A solvent so allowing transport of substances;
3. High (specific) heat capacity so buffers changes in temperature;
4. Large latent heat of vaporisation so provides a cooling effect (through evaporation);
5. Cohesion (between water molecules) so **supports columns **of water (in plants);
   For ‘columns of water’ accept ‘transpiration stream’.
   For ‘columns of water’ accept ‘cohesion-tension (theory)’.
6. **Cohesion **(between water molecules) so produces surface tension supporting (small) organisms;
   Allow other suitable properties but must have a valid explanation. For example
   * ice floating so maintaining aquatic habitat beneath
   * water transparent so allowing light penetration for photosynthesis

Question 7

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

Answer 7

IRON IONS:
1. Haemoglobin binds/associates with oxygen
OR
Haemoglobin transports/loads oxygen;
(ignore reference to 2+ or 3+ in Fe2+ or Fe3+)

SODIUM IONS:
2. Co-transport of glucose/amino acids (into cells);
3. (Because) sodium moved out by active transport/Na - K pump;
4. Creates a sodium concentration/diffusion gradient;
5. Affects osmosis/water potential;

PHOSPHATE IONS:
6. Affects osmosis/water potential;
(accept 5. OR 6. - not both)
7. Joins nucleotides/in phosphodiester bond/in backbone of
DNA/RNA/in nucleotides;
8. Used in/to produce ATP;
(reject ‘energy produced’)
9. Phosphorylates other compounds (usually) making them more reactive;
10. Hydrophilic/water soluble part of phospholipid bilayer/membrane;

(must have MP1 for 5 max)
(3 max for sodium and 3 max for phosphate)