Energy Transfer In and Between Organisms

Question 1

Describe the light-dependant reaction in plants.

Answer 1

1. Electrons are excited to a higher energy level and passes to an electron acceptor.
2. Electrons move down electron transfer chain which creates energy.
3. Energy is used to join ADP and Pi to form ATP.
4. Photolysis of water produces 2H+, 0.5 oxygen and 2e-.
5. H+ is used to reduce NADP and for chemiosmosis.
6. The electrons are used to replace the electrons used in photosystem II.

Question 2

Describe the process of chemiosmosis.

Answer 2

1. From photolysis, there is a build up of H+ ions in stroma.
2. H+ is pumped into thylakoid space by proton pump to maintain their high concentration.
3. H+ diffuses down their electrochemical gradient through ATP synthase.
4. ADP + Pi -> ATP

Question 3

Describe the light independent reaction of photosynthesis.

Answer 3

1. Carbon dioxide combines with RuBP.
2. Produces two GP using rubisco.
3. GP is reduced into two triose phosphate using reduced NADP and energy from ATP.
4. Triose phosphate converted to glucose.

Question 4

Name 5 environmental factors which limit the rate of photosynthesis and explain why.

Answer 4

1. Light wavelength - provides energy - optimum is red and blue as absorbs light.
2. Light intensity - provides energy, rate increases until saturation point.
3. Temperature - enzymes inactive at low and denature at high.
4. Carbon dioxide - too much and stomata will close.
5. Water - change will affect ROR.

Question 5

What are the four stages of respiration?

Answer 5

1. Glycolysis.
2. Link Reaction.
3. Kreb’s Cycle.
4. Electron Transfer Chain.

Question 6

Describe the process of glycolysis.

Answer 6

1.