Light Dependent Reaction

Question 1

Where does it occur?

Answer 1

On the thylakoid membranes on chloroplasts

Question 2

Adaptations of the membranes?

Answer 2

Create a large SA to increase number of LDR’s that can occur

Question 3

1st step?

Answer 3

Light energy hits molecules of H2O- splitting H2O into electrons, H+ ions and O2
Oxygen is releases as a waste product
PHOTOLYSIS

Question 4

2nd step?

Answer 4

Light energy hits photosystem 2 where it excites a pair of electrons in photoionisation to a higher energy level

Question 5

3rd step?

Answer 5

The excited electrons leave the photosystem and pass along a series of electron carrier proteins in the ETC
This releases energy, allowing the H+ ions to be pumped across the thylakoid membranes into the thylakoid space (from the stroma to the thylakoid lumen) creating a proton gradient

Question 6

4th step?

Answer 6

The ions diffuse back out of the thylakoid space via ATP synthase (facilitated diffusion) - phosphorylates ADP -> ATP (chemiosmosis)
ATP is produced on the thylakoid membranes by chemiosmosis
Electron carriers are reduced (gain an electron) and oxidised as they lose an electron by passing it onto the next carrier

Question 7

5th step?

Answer 7

Light energy hits photosystem 1- the electrons are used to reduce NADP into NADPH
NADPH is produced when H+ ions in the stroma and electrons from ETC combine with NADP
ATP and reduced NADP are passed to the LIR

Question 8

Chloroplast structure?

Answer 8

Surrounded by a double membrane envelope filled with stroma
Internal membranes contain flattened, fluid-filled sacs (thylakoids)
Grana are a stack of thylakoids