C1.2 Photosynthesis

What are photosynthesis pigments?

Coloured molecules that absorb light energy for photosynthesis

4 photosynthesis pigments and their colours

Chlorophyll A is yellow/green
Chlorophyll B is blue/green

Carotenoids are orange

Xanthophylls are yellow

What is a transducer?

A receptor cell that converts light/chemical/mechanical energy into an electrical signal

What does an absorbance spectrum show?

The amount of light energy of each wavelength that is absorbed by a pigment measured by a colorimeter

What does an action spectrum show?

Rate of photosynthesis at different wavelengths of light

What did Engelmann’s experiment show?

Aerobic bacteria moved to red/orange and blue/violet regions when light was on because photosynthesis was occurring, releasing oxygen

What and where are photosynthesis?

Light harvesting complexes embedded in the thylakoid membrane

2 parts of the photo system structure

The base and the funnel

Role of the base of the photsystem structure

The reaction centre where chloroplast A is the primary pigment

Role of the funnel of the photsystem structure

Also known as antenna, has other, accessory pigments which absorb and transfer energy towards the reaction centre

What happens when sufficient energy has been transferred to the reaction centre?

An electron is boosted to a higher energy level

Reactant and products in light dependant photosynthesis

reactant - water
product - hydrogen
also produced - ate and reduced NADP

What is photolysis?

The splitting of water molecules using light energy

What is cyclic photophosphorylation?

The production of ATP using electrons from PSI

What is non-cyclic photophosphorylation?

The production of ATP using electrons from PSII travelling to PSI

What is PSI?

The collection of pigment molecules, having a reaction centre of chlorophyll a with an absorption peak of 700nm

What is PSII?

Collection of pigment molecules, having a reaction centre of chlorophyll a with an absorption peak of 680nm

What occurs in cyclic photophosphorylation?

Electrons passed down ETC to PSI, ATP is produced

What occurs in non-cyclic photophosphorylation?

Photolysis occurs, oxygen, NADP and ATP is produced, electrons pass down ETC from PSII to PSI

Process of photophosphorylation

Electrons pass down ETC and then transferred to a higher energy level, energy released is used to pump protons from the stroma to the thylakoid lumen increasing proton concentration and lowering pH, protons then move by facilitated diffusion back to the stroma

Where does the light independent cycle occur?

Stroma of chloroplast

Other name for light independent stage

Calvin cycle

1st stage of the light independent stage

Carbon dioxide is fixed by ribulose biphosphate by RUBISCO to form a 6C unstable intermediate

2nd stage of the light independent stage

The 6C compound breaks down to form 2 glycerate-3-phosphate molecules

3rd stage of the light independent stage

Glycerate-3-phosphate is reduced using reduced NADP and converted into triose phosphate using energy from the ATP from the LD stage

4th stage of the light independent stage

1 of the 6 triose phosphates are used to synthesise glucose

5th stage of the light independent stage

5 of the 6 triose phosphates are used to regenerate RuBP using energy from ATP from LD stage, ribulose phosphate is formed first

How many carbon cycles are needed to produce 2 triosephosphates? How much glucose can then be made?

6 cycles → 1 glucose molecule