Photosynthesis

Question 1

LIS/Calvin Cycle

- Describe carbon-fixation

Answer 1

• CO2 diffuses in via the stomata.
• It then diffuses through the Cell Surface Membrane, cytoplasm, and chloroplast membranes into the stroma of the chloroplast.
• CO2 reacts with RUBP through the enzyme rubisco.
  1 + 5 + 6C
• This forms an unstable intermediate which immediately splits into 2GP molecules (3C)

Question 2

LIS/Calvin Cycle

- Explain the reduction stage

Answer 2

• Reduced NADP(NADPH) and ATP supply energy, H atoms and electrons to reduce and phosphorylate GP to form TP.

Question 3

LIS/Calvin Cycle

Describe the regeneration stage

Answer 3

Cycle regenerates RuBP by using 5TP to regenerate 3RuBP every 3 turns.

Question 4

Where is rubisco encoded and synthesized?

Answer 4

Chloroplast and it’s circular DNA

Question 5

Every turn of the Calvin Cycle what happens?

Answer 5

1 CO2 molecule is fixed.

2GP is produced therefore producing 2TP.

Question 6

Every three turns of the Calvin Cycle, what happens?

Answer 6

6TP is made and 1 molecule of TP(3C) is released.

Remaining 5 TP(15C) are used to make 3RuBP.

Question 7

What happens every six turns of the calvin cycle?

Answer 7

12 TP Molecules formed:

• 10 TP is used to make RuBP
• 2TP required for glucose (6C) is produced.
• 18ATP and 12NADPH is used.

Question 8

Where does the NADP from the used NADPH go back to?

Answer 8

LDS to be reduced again.

Question 9

What is the site of the LIS?

Answer 9

Stroma of the chloroplast

Question 10

What is the difference between PSII and PSI?

Answer 10

PSII has 680nm chlorophyll and PSI has 700nm chlorophyll.

Question 11

What does non-cyclic photophosphorylation involve?

Answer 11

PSII and PSI.

ATP and NADPH is produced.

Question 12

How can light be a limiting factor of photosynthesis?

Answer 12

Low - reduce the amount of ATP + NADPH + O2 produced during LDS.

• HIgh GP
• Low RuBP + TP

Question 13

How can CO2 be a limiting factor of photosynthesis?

Answer 13

• Low - Less RuBP converted to GP
• Too High - Plant wilts as stomata opens to increase gas exchange but this leads to an increase in the rate of transpiration. This causes the plant to lose water and plasmolyzes cells for them to end up flaccid and wilt.

Question 14

How can temperature act as a limiting factor for photosynthesis?

Answer 14

Many reactions involve enzymes (e.g rubisco) so:

• Low-30°C = Increase
• 30°C+ = could lead to photorespiration where O2 competes with CO2 for rubisco active site.
• 45°C+ + enzymes denature

Question 15

How many carbons are in TP?

Answer 15

3

Question 16

How many carbons are in GP?

Answer 16

3

Question 17

Which enzyme is used in carbon fixation?

Answer 17

Rubisco

Question 18

How many carbons does RuBP have?

Answer 18

5

Question 19

Describe the LIS of Photosynthesis

Answer 19

Calvin Cycle

Carbon-fixation
- CO2 diffuses in via the stomata.
- It then diffuses through the Cell Surface Membrane, cytoplasm, and chloroplast membranes into the stroma of the chloroplast.
- CO2 reacts with RUBP through the enzyme rubisco.
1 + 5 + 6C
- This forms an unstable intermediate which immediately splits into 2GP molecules (3C)

Reduction
- Reduced NADP(NADPH) and ATP supply energy, H atoms and electrons to reduce and phosphorylate GP to form TP.

Regeneration
- Cycle regenerates RuBP by using 5TP to regenerate 3RuBP every 3 turns.

Question 20

What does the LIS of Photosynthesis involve?

Answer 20

Calvin Cycle

• Carbon-fixation
• Reduction
• Regeneration

Question 21

What are the products of LDS?

Answer 21

ATP, NADPH

Question 22

What is used up during one cycle of the Calvin cycle?

Answer 22

(RuBP , CO2, 3ATP, 2NADPH)

Question 23

Where does the LDS occur?

Answer 23

Thylakoid Membrane/Granum

Question 24

What happens to the H+ ions in photolysis?

Answer 24

Used to reduce NADP