Photosynthesis

Question 1

Photolysis

Answer 1

H20 -> 1/2 O2 + 2e- + 2H
light energy is absorbed splits and water

Question 2

Photoionization of water

Answer 2

Light energy is absorbed by chlorophyll which results in e- being excited + leaving the chlorophyll

Question 3

LDR useful products

Answer 3

1. ATP
2. Reduced NADP

Question 4

Location of LDR

Answer 4

Thylakoid membrane

Question 5

Location of LIR

Answer 5

Stroma

Question 6

LIR useful products

Answer 6

organic substance (hexose sugars eg. glucose)

Question 7

Role of RuBISCO

Answer 7

catalyze the combination of RuBP and CO2

Question 8

What are the x stages of the light dependent reaction ?

Answer 8

1. Photoionisation of PSII
2. Photolysis of water
3. Photoionisation of PSI
4. Active transport of H+ ions
5. Oxidative phosphorylation
6. Reducing NADP

Question 9

Describe what happens during photoionisation of PSII

Answer 9

Chlorophyll absorbs light
Electrons excited and move to higher energy level
Electrons move down electron transport chain to PSI

Question 10

Describe what happens during photolysis of water

Answer 10

Light energy splits water molecules into H+, e- and oxygen
The electrons replace those lost from PSII during photoionisation

Question 11

Explain how H+ ions are moved across the thylakoid membrane

Answer 11

The excited electrons from photoionisation lose energy as they move down the electron transport chain
The energy is used to actively transport H+ into the chloroplast

Question 12

Explain how H+ are involved in the synthesis of ATP in chloroplasts

Answer 12

H+ move down their concentration gradient into the stroma
This is via ATP synthase in the thylakoid membrane
The energy synthesises ATP from ADP and Pi

Question 13

Explain why the photoionisation of PSI is important

Answer 13

The excited eletrons are transferred to NADP with H+ to form reduced NADP
This is needed for the light-independent reaction

Question 14

What is chemiosmosis ?

Answer 14

Electrons move down the electron transport chain and creating a proton gradient
This drived ATP synthesis

Question 15

What are the 3 stages of the light-independent reaction?

Answer 15

1. Formation of glycerate 3-phosphate
2. Formation of triose phosphate
3. Regeneration of ribulose bisphosphate

Question 16

Explain how glycerate 3-phosphate (GP) is formed

Answer 16

Ribulose bisphosphate (RuBP) combines with CO2
Forms unstable 6 carbon compound which breaks down to give 2 molecules of glycerate 3-phosphate
Catalysed by Rubisco

Question 17

How does CO2 enter the stroma from the atmosphere?

Answer 17

Diffusion through the stomata
Difussion into the stroma

Question 18

How many molecules of glycerate 3-phosphate (GP) are produced from 1 molecule of CO2 and 1 molecule of ribulose bisphosphate (RuBP) ?

Answer 18

2

Question 19

How many carbon atoms are in ribulose bisphosphate ?

Answer 19

5

Question 20

How many carbon atoms are in glycerate 3-phosphate (GP) ?

Answer 20

3

Question 21

Explain how triose phosphate (TP) is formed from glycerate 3-phosphate (GP)

Answer 21

Glycerate 3-phosphate (GP) is reduced to triose phosphate (TP) using H+ ions

Question 22

How is glycerate 3-phosphate (GP) reduced to triose phosphate (TP) ?

Answer 22

Hydrolysis ATP from the light dependent reaction provide energy
reduced NADP releases H+ to form NADP

Question 23

What two things can triose phosphate (TP) be used for?

Answer 23

1. regenerating ribulose bisphosphate (RuBP)
2. Converted to useful organic substances

Question 24

Which two stages in the light independent reaction is ATP hydrolysed ?

Answer 24

Reduction of glycerate 3-phosphate (GP) to triose phosphate (TP)
Regeneration of ribulose bisphosphate (RuBP)

Question 25

Which 3 factors can limit the rate of photosynthesis?

Answer 25

1. Light Intensity
2. Temperature
3. CO2 concentration