11 - Photosynthesis

Question 1

LIGHT DEPENDENT REACTION

Answer 1

1. light energy excites electrons in chlorophyll and electrons are emitted, oxidising the chlorophyll by photoionization
2. these electrons are replaced by electrons released from photolysis of water, reducing the chlorophyll
3. emitted electrons pass along the electron transfer chain in a series of redox reactions
4. at each stage, energy is released and is used to combine ADP and Pi to form ATP by chemiosmosis
5. NADP is the final electron acceptor and forms reduced NADP which goes on to be used in the LIR
6. oxygen is a by-product of this process

Question 2

CHEMIOSMOSIS

Answer 2

1. protons are pumped from the stroma into the thylakoid by proton pumps in thylakoid membrane
2. energy for this process comes from the electrons released in the photolysis of water
3. the photolysis of water also produces protons, increasing the proton concentration in the thylakoid
4. maintains a high concentration of protons in the thylakoid, and low concentration in the stroma
5. protons leave the thylakoid via ATP synthase channels
6. as the protons pass through the ATP synthase they cause a change in the structure of the enzyme which catalyses the formation of ATP from ADP and Pi

Question 3

PHOTOLYSIS

Answer 3

2 H2O&raquo_space; 4H+ + 4e- + O2

Question 4

LIGHT INDEPENDENT REACTION (CALVIN CYCLE)

Answer 4

1. CO2 diffuses into stroma where it reacts with RuBP (5C), catalysed by rubisco
2. produces two molecules of GP (3C)
3. reduced NADP from LDR is used to reduce GP to TP (3C)
4. NADP goes back to LDR to accept more electrons
5. some TP converted into organic molecules
6. most TP used to regenerate RuBP using ATP from LDR

Question 5

net gain of light dependent reaction

Answer 5

F