5.7

Question 1

State the precise site of the light dependent reactions

Answer 1

In the thylakoid membrane in granum, in the chloroplast

Question 2

Explain photolysis

Answer 2

The split of a compound with the presence of light energy

Question 3

State the term used to describe the production of ATP via the light dependent reaction. Explain why it is given this name.

Answer 3

Photophosphorylation
Photo - light needed
Phosphory - the addition of a phosphate group

Question 4

State the term used to describe the process by which electrons move down the electron transport chain. Explain why the term is used.

Answer 4

Photoionisation
Photo - light needed to excite electron
Ionisation - chlorophyll becoming ionised (removal of electron as it moves down the transport chain)

Question 5

State the three products of the light dependent stage

Answer 5

ATP, NADPH (reduced NADP) and O2

Question 6

State the role of the three products of the light dependent stage

Answer 6

ATP - energy storage molecule
NADPH - electron carrier
O2 - waste product

Question 7

Describe the process of the light dependent stage (4/5 marks)

Answer 7

1. Light energy breaks down water (photolysis), producing H+ ions, electrons and oxygen in the thylakoid lumen
2. Electrons start in Photosystem II, absorb light and are excited (photoionisation), and move through electron transport chain whilst releasing energy (electrons from more photolysis of water replace those lost here)
3. The energy synthesises ATP, and the electron reaches Photosystem I where it is excited again.
4. The electrons attach to NADP with a H+ ion to reduce it, forming NADPH