L7 light dependant reaction (ETT)

What is the structure of chloroplasts?

3 membranes: Outer, inner, and Thylakoid (where light reaction takes place)

3 compartments: Intermembrane space, Stroma (calvin cycle takes place), thylakoid space

Function of chloroplasts

responsible for photosynthesis, converting light energy into chemical energy stored as glucose.

Thylakoid function

Where light dependant reactions occur. Multiple stacks are called Grana.

What goes into photosystem II, and what comes out?

Photosystems containing chlorophyll absorb light energy. The light energy is transferred to the chlorophyll reaction centre, causing electrons in the reaction centre to become energised. These high energy electrons leave and continue through the electron transport chain. To replace the electrons, water is split creating 2H+ and ½ O2 and 2 electrons.

Where do the electrons go after PSII

1. Move through the cytochrome complex (which pumps ions from stroma into thylakoid space, creating a concentration gradient).

2. And then into PSI (where the electrons get energised again thanks to light energy).

3. Then move into Complex2 of the electron transport chain (Which use the electrons, and H+, to reduce NADP to NADPH).

Why is the Cytochrome complex important?

It uses energy released from the electrons moving through the ETT, to pump H+ from the stroma into the thylakoid space. This creates an electro-chemical gradient. The H+ flows down the concentration gradient (back into the stroma) through a channel in ATP synthase, releasing energy. ATP synthase uses this energy to turn ADP into ATP.

Main inputs and outputs of photosynthesis

Main inputs are 6CO2, water 6H2O, and sunlight. Main outputs are 6 carbon glucose and 6oxygen.

Endosymbiosis

The theory that chloroplasts and mitochondria originated from free-living prokaryotes that were engulfed by ancestral eukaryotic cells.

Why is the endosymbiotic theory significant?

It explains the presence of double membranes and circular DNA in chloroplasts and mitochondria, supporting their origin from independent prokaryotic organisms.

Products of the light dependant reactions.

ATP and NADPH and O2