Photosynthesis

Question 1

Transducers

Answer 1

As transducers, chloroplasts can change energy from one form into another, in this case light energy into chemical energy

Question 2

Photosynthetic pigments

Answer 2

Chlorophylls
Absorb red and blue-violet regions of the spectrum e.g chlorophyll a and chlorophyll b

Carotenoids
Absorb light energy from the blue-violet region of the spectrum e.g B-carotene and xanothophylls and act as a accessory pigments

Question 3

Light harvesting, what are the chlorophylls and accessory pigmented groups called?

Answer 3

Antenna complexes

Question 4

2 types of reaction centre

Answer 4

Photosystem 1 (PSI) chlorophyll a, with the absorption peak of 700nm, also called P700

Photosystem 2 (PSll) chlorophyll a, with an absorption peak of 680nm p680

Question 5

Non-cyclic phosphorylation

Answer 5

Involves both photosystem (1&2) generating 2 ATP molecules and NADPH, photolysis generate oxygen

1. Light energy strikes chlorophyll (PS2) exciting it’s electrons, boosting them to a higher energy level
2. Electrons are accepted by an electron carrier in the thylakoid membrane
3. The oxidised chlorophyll removes electrons from water, producing protons and oxygen (photolysis). Occurs in the thylakoid space
4. As electrons pass from carrier to Carrier, electron energy is lost, which pumps protons from stroma to thylakoid space. As protons flow back through the stalked particle. ADP is phosphorylated; 2 ATP are made in total
5. Electrons enter photosystem 1 where light excites them, boosting them to an even higher energy level
6. electrons enter a final electron carrier
7. Electrons and protons reduce NADP to NADPH which pass to the Calvin cycle, with 2 ATP made

Question 6

Calvin cycle

Answer 6

CO2 diffuses into the leaf via stomata dissolving into the Palisade mesophyll cells

CO2 combines with a 5C compound ribulose biphosphate with rubisco to help

This forms an unstable 6C compound

This immediately splits into 2 molecules of glucose 3 phosphate

Using 1 ATP molecule from the light reaction GP is reduced to triode phosphate using H from NADPH

Triode phosphate molecules combine in pairs to form hexose sugars

5 out of the 6 triode phosphates molecules are produced to regenerate ribulose biphosphate using ATP from the light dependent reaction to supply energy and phosphate - allows cycle to continue