light dependent ps

Question 1

Use information in the diagram to explain

(i) the role of chlorophyll in photolysis;

Answer 1

Absorbs light / energy;
Loses electrons / becomes positively charged / is oxidised;
Accepts electrons from water / from OH– which causes more water
to dissociate / pulls equilibrium to the right;

Question 2

how the energy of light is converted into chemical energy in the light-dependent reactions.

Answer 2

Electrons raised to higher energy level / electrons excited;
Use of electron carriers / cytochromes / acceptors;
For production of ACT

Question 3

Crops use light energy to produce photosynthetic products.

Describe how crop plants use light energy during the light-dependent reaction.

___________________________________________________________________

Answer 3

Excites electrons / electrons removed (from chlorophyll);

Accept: higher energy level as ‘excites’.

2. Electrons move along carriers/electron transfer chain releasing energy;

Accept: movement of H+/protons across membrane releases energy.

Reject: ‘produces energy’ for either mark but not for both.

3. Energy used to join ADP and Pi to form ATP;

Reject: ‘produces energy’ for either mark but not for both.

Accept: energy used for phosphorylation of ADP to ATP

Do not accept P as Pi but accept phosphate.

4. Photolysis of water produces protons, electrons and oxygen;
5. NADP reduced by electrons / electrons and protons / hydrogen;

Question 4

Atrazine binds to proteins in the electron transfer chain in chloroplasts of weeds, reducing the transfer of electrons down the chain.

Explain how this reduces the rate of photosynthesis in weeds.

Answer 4

Reduced transfer of protons across thylakoid membrane

OR

Reduced chemiosomotic gradient / proton gradient across thylakoid membrane;

2. (So) less ATP produced;
3. (So) less reduced NADP produced;

Accept NADPH / NADPH2 / NADPH+

Reject reduced NAD

4. (So) light-independent reaction slows / stops;

OR

Less reduction of GP to triose phosphate.

Question 5

When treated with Atrazine, weeds have been shown to give off small amounts of heat.

Suggest an explanation for this observation

Answer 5

Idea that energy is released from high energy / excited electron/s (that were lost from chlorophyll)

Question 6

ATP and reduced NADP are two products of the light-dependent reactions. Describe one function of each of these substances in the light-independent reactions.

ATP _______________________________________________________________

Answer 6

ATP) Provides energy for GP → TP / provides P for RuP / TP → RuBP;

Question 7

Give two products of the light-dependent stage of photosynthesis.

Answer 7

Reduced NADP;

Accept NADPH/ NADPH+/NADPH2

1

ATP;

Question 8

The products of the light-dependent stage are used in the light-independent stage of photosynthesis. What are these products used for?

Answer 8

To incorporate carbon dioxide) to make sugars/glucose/fructose