Light Dependant Reaction

What is photophosphorylation?

The formation of ATP using light energy

What are the two types of photophosphorylation?

Non cyclic and cyclic photophosphorylation

What are the products of non cyclic photophosphorylation?

ATP reduced NADP and oxygen

What are the four main stages of non cyclic photophosphorylation?

Light absorption electron transfer photolysis and chemiosmosis

What happens when light is absorbed by photosynthetic pigments?

Electrons become excited

What is photoactivation?

The loss of excited electrons from photosystem reaction centres

Which photosystems are involved in non cyclic photophosphorylation?

PSI and PSII

What happens to electrons after leaving PSII?

They pass along an electron transport chain

What happens as electrons pass along the electron transport chain?

Energy is released

What is photolysis?

The light driven splitting of water

What is the equation for photolysis?

2H2O → 4H+ + 4e- + O2

What replaces electrons lost from PSII?

Electrons from photolysis of water

What happens to the protons produced by photolysis?

They contribute to the proton gradient and reduce NADP

What happens to oxygen produced by photolysis?

It is released as a by product

Where are protons pumped during non cyclic photophosphorylation?

Into the thylakoid space

What creates the proton gradient?

Active transport of protons into the thylakoid space

Where is the proton concentration highest?

In the thylakoid space

How do protons move through ATP synthase?

By facilitated diffusion into the stroma

What powers ATP synthase?

The movement of protons down the proton gradient

How is ATP formed?

ADP combines with inorganic phosphate

Where is ATP produced?

In the stroma

How is reduced NADP formed?

NADP gains electrons and protons

Where is reduced NADP formed?

In the stroma

What is reduced NADP used for?

The light independent reaction

What does cyclic photophosphorylation produce?

Small amounts of ATP

Which photosystem is involved in cyclic photophosphorylation?

PSI only

When does cyclic photophosphorylation typically occur?

When NADP is unavailable

Does cyclic photophosphorylation produce reduced NADP?

No

Does cyclic photophosphorylation produce oxygen?

No

What happens to electrons in cyclic photophosphorylation?

They return to PSI

How does cyclic photophosphorylation produce ATP?

Electrons pass along an electron transport chain and generate a proton gradient

What is the main difference between cyclic and non cyclic photophosphorylation?

Cyclic produces ATP only while non cyclic produces ATP reduced NADP and oxygen