4.3 - Light-Dependent reaction

Question 1

What two purposes does light energy have in the LDR?

Answer 1

• To add an inorganic phosphate molecule to ADP creating ATP.
• To split H20 into H+ and OH- ions. (photolysis)

Question 2

What is Oxidation?

Answer 2

Gain of Oxygen/Loss of Hydrogen/Loss of electrons.

Question 3

What is Reduction?

Answer 3

Loss of Oxygen/Gain of Hydrogen/Gain of electrons.

Question 4

What happens when light hits a chlorophyll molecule?

Answer 4

Chlorophyll absorbs light energy. Causes excitation of pair of electrons within chlorophyll molecule. They then leave chlorophyll. Taken up by Electron Carrier.

Question 5

What comment could you make (redox) regarding the chlorophyll and electron carrier after the electrons have transferred?

Answer 5

Chlorophyll: lost electrons - oxidised.

Electron Carrier: gained electrons - reduced.

Question 6

What is the Electron Transport Chain and where is it found?

Answer 6

Chain of electron carriers in the thylakoid’s membrane.

Question 7

How does the E.T.C. work?

Answer 7

Via redox reactions. Each successive carrier at slightly lower energy level than previous carrier. Causes electrons to lose energy at each stage. This released energy used for combining Pi and ADP to make ATP.

Question 8

What is photolysis.

Answer 8

When water molecules are split using light energy (creates e-, H+, O2).

Question 9

What happens to the electrons from photolysis?

Answer 9

They replace the lost electrons in chlorophyll.

Question 10

What happens to the H+ ions from photolysis?

Answer 10

Taken up by NADP, causing reduction. Therefore causes reduced NADP releases energy and transfers to the LIR.