3.5.1.1 - Photosynthesis (Light Dependent Reactions)

Question 1

Describe how NADP+ is reduced in the LDR of photosynthesis.

Answer 1

2e^- from electron carrier protein (originally from chlorophyll) are gained.

H+ is gained from stroma.

Question 2

What are the products of the light dependent reactions of photosynthesis?

Answer 2

ATP

NADPH (Reduced NADP)

Oxygen

Question 3

Identify the labels.

Answer 3

Question 4

Identify the labels.

Answer 4

Question 5

Why is ATP sometimes referred ot as an immediate energy source of energy?

Answer 5

Because only one bond needs ot be broken to release energy.

ATP is rapidly resynthesised.

Question 6

In biology what is meant by OXIDATION?

Answer 6

The loss of electrons

The loss of hydrogen

The gain of oxygen

Question 7

Identify the labels.

Answer 7

Question 8

For what are the products of the light dependent reactions used for?

Answer 8

NADPH and ATP are required in the light independent reacitons of photosynthesis (Calvin cycle)

Oxygen is used in respiraiton or exits the plant via the stomata.

Question 9

Why does the plant need to carry out the Calvin cycle and respiration if the light dependent reactions produce ATP?

Answer 9

Not enough ATP is produced.

ATP is difficult to transport around the plant.

ATP can not be produced in the dark.

Not all plant cells contain chlorophyll

ATP is not a stable store of energy.

Question 10

Identify the labels.

Answer 10

Question 11

In biology, what is meant by REDUCTION?

Answer 11

The gain of electrons.

The gain of hydrogen.

The loss of oxygen.

Question 12

Describe the Light Dependent Reactions of photosynthesis.

Answer 12

1. Light enters chloroplast and excites 2 electrons in chlorophyll transmembrane protein (photosystem II) spanning thylakoid membrane.
2. 2e^- leave PSII (oxidation) and move to Proton pump (reduction).
3. Proton pump actively transports H+ from stroma into thylakoid space creating an electrochemical gradient.
4. 2e^- leave Proton pump (oxidation) and move to electron carrier (PSI - reduction).
5. H+ ions in thylakoid space diffuse through ATP Synthase, providing the energy to catalyse the formation of ADP + Pi -> ATP
6. 2e^- and H+ move onto NADP+ to make NADPH (reduced NADP).
7. Chlorophyll’s 2e^- are replaced via the photolysis of water in the thylakoid space to give 2e^- + 2H+ + 1/2O₂

Question 13

Identify the labels.

Answer 13

Question 14

Identify the labels.

Answer 14

Question 15

What does the diagram show?

Answer 15

The thylakoid membrane of a chloroplast.

Where the light dependent reactions of photosynthesis take place.

Question 16

What is NADP+?

Answer 16

A coenzyme that works alongside an enzyme, in this case it is a hydrogen carrier and electron acceptor.

It works alongside the enzyme: dehydrogenase

Question 17

How can we measure the rate of the light dependent reactions of photosynthesis?

Answer 17

Measure the volume of oxygen produced.

Over time.

Question 18

In the light-dependent reaction of photosynthesis, light energy generates ATP. Describe how. (5 marks)

Answer 18

1. Light (energy) excites / raises energy level of electrons in chlorophyll;
2. Electrons pass down electron transfer chain;
3. (Electrons) reduce carriers / passage involves redox reactions;
4. Electron transfer chain / role of chain associated with chloroplast
   membranes / in thylakoids / grana;
5. Energy released / carriers at decreasing energy levels;
6. ATP generated from ADP and phosphate / Pi / phosphorylation of ATP;

Question 19

When investigating how light intensity affects plant growth what variables should you control?

Answer 19

temperature

concentration carbon dioxide

volume of water

concentation of ions in soil

pH of soil