Electron Transport Chain
Non Cyclic
- Light dependant reaction takes place inside the thylakoid in the chloroplast of a plant cell
1. Light hits PSII (photosystem 2) which absorbs the wavelength of 680 in light. This causes a photon to bounce on thePSII until it hits a reaction centre, where an electron is released.
2. This causes the the splitting of water by a Z protein to acculmulate free electrons, protons (H+) and an oxygen molecule. This process is called "photolysis".
3. The electron then moves to the PQ. While this is happening, a hydrogen proton from the chloroplast stroma is pumped through the PQ and makes PQH2.
4. The electron then moves to b6f, while the hydrogen proton is pumped out to the thylakoid lumen.
5. the electron then enters the PC, then through PSI (photosystem 1, with p700) where light hits again to excit the electron.
6. Electron then moves to Fd, to FNR where the electron turns NADP to NADPH with a H+ floating in the stroma.
Cyclic
1. When there is insufficent amounts of light, the electron is passed from PSI to fd to b6f where a hydrogen proton is pumped through to the thylakoid. The electron continues to the PC then back to the PSI.
2. This process generates ATP from the transition of the proton to the thylakoid, but does not make NADPH, since there is not enough light and ATP carries more energy.
Generating ATP
1. Since there is a high concentration of H+ protons in the thylakoid lumen, the pH level is high and unbalanced compared to the stroma.
2. The H+ are pumped through ATPase, and ADP is turned into ATP.
Calvin Cycle
Phase #1- carbon fixation
1. 3 RuBP (3 p-c-c-c-c-c-p) [15 carbons] combine with 3 CO2 from the outside with the help of the enzyme rubisco to make 3(p-c-c-c-c-c-c-p) [18 carbons]
Phase #2-reduction
2. This stucture is unstable so it breaks in half to make six 3-phosphateglyercate or 3PGA. (6 c-c-c-p) [18 carbons] Since there is only one phosphate at the end, this stucture is very polar.
3. Thus another phosphate is added to the other end. ATPs give 6 phosphates, and makes ADPs. Now the structure is stable and is called 1,3-bipohsophateglycerate. (6 p-c-c-c-p) [18 carbons]
4. Next NADPH comes and takes a phosphate away to makes NADP+. The phosphate left with the H in NADPH. Now the product is glyceraldehyde-3-phosphate or G3P or PGAL (6 c-c-c-p) [18 carbons]
5. One G3P comes out so 5 G3Ps left. [15 carbons]
*This G3P is later made into glucose. Since there is only 3 carbons in a G3P, the calvin cycle must be run twice.*
Phase #3-regeneration of CO2 acceptor RuBP
6. Through a series of reactions and using 3 ATPs, the 5 G3Ps (5 c-c-c-p) are turned into 3 RuBPs (3 p-c-c-c-c-c-p) [15 carbons] and the cycle is complete.
