Photosynthesis

Question 1

Where does the light independent reaction occur?

Answer 1

Stroma

Question 2

Where does the light dependent reaction occur?

Answer 2

Thylakoids

Question 3

What is photophosphorylation?

Answer 3

Adding inorganic phosphate to ADP to make ATP

Question 4

What is photolysis?

Answer 4

Splitting water into H+ ions, electrons and oxygen

Question 5

What is photoionisation?

Answer 5

Light energy absorbed by chlorophyll
Electrons emitted/lost

Question 6

What are the products of the light dependent reaction?

Answer 6

ATP and reduced NADP (NADPH)

Question 7

What is chemiosis?

Answer 7

H+ across a membrane to generate ATP

Question 8

Steps of the light dependent reaction (LDR)

Answer 8

1. Light is absorbed by chlorophyll. Electrons are lost/emitted. PHOTOIONISATION
2. Water is split into hydrogen ions (H+), electrons and oxygen. PHOTOLYSIS
   The oxygen is used for respiration or diffuses out of the cell. The electrons are used to replace the ones lost from chlorophyll.
3. Electrons pass through electron carriers in the membrane (they are reduced and oxidised).
4. Electron combines with proton to form H+, it reduced NADP to form NADPH.
5. Greater concentration of H+ in the thylakoid. Move through the ATP synthase channel which changes its shape. Allows ADP + Pi —> ATP
   PHOTOPHOSPHORYLATION

Question 9

Photolysis equation

Answer 9

2H2O —> 4H+ + 4e- + O2

Question 10

What happens to the products of photolysis?

Answer 10

e - = replace electrons lost from chlorophyll
oxygen = respiration or diffuses out of the cell
H+ ions = move out of thylakoid space and used to reduce the NADP

Question 11

Steps of the light independent reaction (LIR)

Answer 11

1. Carbon dioxide reacts with ribulose biphosphate (RuBP) to form 2 molecules of glycerate 3-phosphate.
   This is catalysed by the enzyme rubisco.
2. ATP and reduced NADP are used to reduce GP to triose phosphate.
3. Some of the triose phosphate is used to regenerate RuBP in the Calvin Cycle.
4. Some of the triose phosphate is converted into useful organic substances.

Question 12

Where is rubisco found in the cell?

Answer 12

Stroma

Question 13

Describe the Light Independent Reaction/Calvin Cycle (6 marks)

Answer 13

CO2 combines with RuBO (ribulose biphosphate) using the enzyme Rubisco
Produces 2 GP molecules (glycerate-3-phosphate)
GP reduced to 2 molecules of TP (triose phosphate)
Using reduced NADP
Using energy from ATP
TP converted into organic substances e.g glucose