LDR

Question 1

1. Where does the Light dependent reaction happen?

Answer 1

In the membranes of the thylakoids inside chloroplasts.

Question 2

2. What happens to the chlorophyll when it absorbs light energy?

Answer 2

The electrons become excited, raising their energy level and are released from the chlorophyll and accepted by the electron carriers in the electron transport chain. This is photoionisation.

Question 3

3. Where do the electrons come from to replace the ones lost to the etc?

Answer 3

The photolysis of water to make O2, H+ ions and electrons

Question 4

4. What is the energy from the transport of electrons along the chain used for?

Answer 4

Pumping hydrogen ions into thylakoid

Question 5

5. What happens to the electrons after they are taken into photosystem I?

Answer 5

Light energy are excited again to an even higher level and are transferred to NADP along with a H+ ions, forming reduced NADP

Question 6

6.How is an electrochemical gradient used to generate ATP?

Answer 6

ATP production occurs when hydrogen ions (protons) diffuse down an electrochemical gradient through molecules of the enzyme ATP synthase which changes the shape of ATP synthase causing the production of ATP. The movement energy is transferred to chemical energy in the phosphate bond of ATP.

Question 7

7. What is chemiosmotic theory?

Answer 7

The process of hydrogen ions moving across the thylakoid membrane, into the stroma down the electrochemical gradient, driving the production of ATP.

Question 8

8. What is NADP?

Answer 8

The coenzyme used to photosynthesis to transfer hydrogen from the LDR to the LIR

Question 9

9. What are the products of the LDR?

Answer 9

ATP and reduced NADP

Question 10

10. What is meant by the term photophosphorylation?

Answer 10

Light is absorbed by chlorophyll and this is linked to the production of ATP by the phosphorylation of ADP with an inorganic phosphate.

Question 11

11. What is meant by the term photoionisation

Answer 11

Light energy is absorbed by chlorophyll. The electrons become excited, raising their energy level and are released from the chlorophyll and accepted by the electron carriers in the electron transport chain. The chlorophyll has therefore been ionised (lost electrons).

Question 12

12. What is a photoautotroph. Give examples.

Answer 12

Organisms that make their own organic molecules such as glucose from inorganic molecules such as carbon dioxide. Plants, algae and some species of bacteria are photoautotrophs.

Question 13

13. Why does the process of photosynthesis give indirect evidence of evolution?

Answer 13

It is the same in all photoautotrophic organisms e.g. plants, algae, some species of bacteria.