Photosynthesis

Question 1

What is the equation for the photolysis of water?

Answer 1

H2O –> 2H+ + 2e- + 1/2O2

Question 2

Name 3 photosynthetic pigments:

Answer 2

Chlorophyll A, Chlorophyll B, Carotene

Question 3

How is photoionisation of chlorophyll triggered?

Answer 3

By the absorption of different wavelengths of light.

Question 4

Where do the light-dependant and independent stages of photosynthesis take place?

Answer 4

Light-dependant - Thylakoid membranes

Light-independent - Stroma

Question 5

Describe the chemiosmotic theory:

Answer 5

In each thylakoid, H+ ions are actively transported to the stroma using proton pumps. The energy used comes from the redox reactions taking place in the electron transport chain and some form when electrons are released during photolysis. An electrochemical gradient is formed and the H+ ions move back in through ATP synthase which catalyses ATP production.

Question 6

What are the products of the light-dependant stage?

Answer 6

Reduced NADP (from the H+ released during photolysis), ATP, and oxygen.

Question 7

What is the first stage of the Calvin Cycle?

Answer 7

Carbon dioxide diffuses into the leaf through the stomata. It then diffuses into the stroma of a chloroplast. It there reacts with a 5-C compound ribulose bisphosphate (RUBP). This catalysed by rubisco. This produces two molecules of 3-carbon Glycerate-3-phosphate (GP).

Question 8

What enzyme catalyses the reaction between RUBP and CO2?

Answer 8

Rubisco.

Question 9

What does reduced NADP do?

Answer 9

It reduces glycerate-3-phosphate (GP) to triose phosphate (TP). This reaction also requires ATP.

Question 10

What is triose phosphate converted into in the Calvin Cycle?

Answer 10

Most regenerate Ribulose biphosphate (RUBP). Some are converted into useful organic molecules such as glucose or lipids.