Light Dependent Reaction

Question 1

LDR

Answer 1

• first stage
• requires light
• light energy and water used to create ATP and reduced NADP needed for LIR

Question 2

What are the stages of LDR?

Answer 2

1. Photolysis
2. Photoionisation of chlorophyll
3. Chemiosmosis
4. Production of ATP and reduced NADP

Question 3

Photolysis of Water?

Answer 3

• photolysis = light splitting
• light energy absorbed by chlorophyll and split into oxygen, H+ and e- (H2O-1/2O2 + 2e- + 2H+)
• H+ picked up by NADP - used in LIR
• passed along chain of electron carrier proteins
• oxygen used for either respiration or diffuses out of leave via the stomata

Question 4

Photoionisation of chlorophyll

Answer 4

• light energy absorbed by chlorophyll
• electrons become excited and leaves the chlorophyll
• so chlorophyll has been ionised by light
• some energy released used to form ATP and reduced NADP in chemiosmosis

Question 5

Chemiosmosis?

Answer 5

1. Electrons that left chlorophyll go along a series of proteins embedded in thylakoid membrane
2. As they move along they release energy and pump protons across the chloroplast membranes
3. Electrochemical gradient created and protons pass through ATP synthase - produces ATP
4. Protons combine with NADP (coenzyme) to become reduced NADP. Protons move from high to low concentration gradient - Chemiosmosis