The light-dependent reaction

Question 1

What is the light dependent reaction?

Answer 1

• occurs in the grana where there’s chloroplasts
• requires light
• produces ATP, NADPH and oxygen

Question 2

How is ATP produced?

Answer 2

• non cyclic: phosphorylation uses energy from ETC

- cyclic phosphorylation: uses NADPH from the chloroplasts by putting electrons back into the ETC to produce more ATP

Question 3

What does photosystem ll do?

Answer 3

• photosystem ll is the first photosystem
• it is struck by light which causes excitation so two electrons are releases
• the electrons are picked up by the RTc and move from molecule to molecule via oxidation reduction reactions
• the electrons then go to photosystem l which is the second photosystem to reoxidise it after it also loses two electrons

Question 4

What is photosystem ll?

Answer 4

• photosystem l is the second photosystem
• it is struck by light causing excitation which releases two electrons that are picked up by the ETC
• the electrons from photosystem l are used to reduce NADP

Question 5

What is photolysis?

Answer 5

• water is hit by a photon if light which produces oxygen, two hydrogen and two electrons
• hydrogen (protons) meets the electrons from photosystem 1 to reduce NADP coenzyme
• new electrons reoxidise photosystem ll so the process can repeat
• oxygen is a waste product but it may be used in respiration