Photosynthesis

Photosynthesis Notes

PHOTOSYNTHESIS

Light-Dependent Reaction

1.Photosynthesis - the production of glucose and oxygen from carbon dioxide and water using light energy trapped by chlorophyll.

2.The process of Photosynthesis involves a lot of redox reactions. Redox = Reduction (Gain an electron) and Oxidation (Lose an electron).

3.PSII acquire electrons from water after it receives light energy from the sun. Photolysis is the process where the sun's energy is required to break apart water into hydrogen and oxygen. (680mm)

4.Electrons are passed on from PSII to PQ; PSII is oxidized and PQ is reduced.  PQ is a helper protein, assists B6F in opening a proton pump channel.

5.In PQ, a gate forms which allows the inflow of hydrogen.

6.Electrons move from PQ to b₆f; PQ is oxidized and b₆f is reduced. b₆f pumps protons across thylakoid membrane from stroma to the thylakoid lumen.

7.PS1 receives light energy (700mm) before it receives electrons from b6f; PSI is reduced and b6f is oxidized.

8.Electrons are passed on from PSI to Fd; PSI is oxidized and Fd is reduced. Electrons are transported from Fd to FNR; Fd is oxidized and FNR is reduced.

9.Electrons are passed on from FNR to NADP; FNR is oxidized and NADP is reduced. A hydrogen proton then bonds with NADP to form NADPH.

10.    Chemiosmosis -chemicals pass through a semi-permeable membrane from a high to low concentration gradient. This allows hydrogen to leave the structure. ADP (along with A) attaches to ATP synthase. After another phosphate joins this association, ATP is formed and hydrogen can exit the structure.

Light Independent Reaction

1.Calvin Cycle- the chemical process that helps to convert potential energy from ATP and NADPH into potential energy stored in glucose. (occurs in the stroma)

2. CO2 reacts with RUBP to form unstable 6 Cintermediate

3.The reaction of CO2 + RUBP is calatlyzed by the enzyme RuBP carboxylase – rubisco

4.  CO2 + RuBP => unstable 6 carbon intermediate 2 molecules of PGA (3 phosphoglycerate)

5.Converting PGA to Glyceraldehyde phosphate (G3P) requires the addition of energy released by ATP and NADPH – (this is the same ATP and NADPH that were just produced in the Light Dependent Reactions)

6. Glyceraldehyde 3 Phospate (G3P) 

◦ Can be used to produced glucose = Potential energy stored in chemical bonds of glucose 

◦ Can be used to make RUBP = Converting G3P to RUBP requires the input of energy from ATP (also created by the light dependent reactions)

7.   3 RuBP are catalyzed in a single Calvin cycle. 6 PGAs = 6 BPGs = 6 G3Ps. 

8.Through a series of reactions, 5 of the G3Ps formed are recycled to form RuBP to initiate another Calvin Cycle.

9.The last G3P leaves the cycle.

10. This means that it requires two cycles to create one glucose.