Calvin Cycle

Question 1

What two abilities does rubisco have

Answer 1

Carboxylating and oxygenating

Question 2

What are the three processes of the CBB cycle

Answer 2

1. Fixation of carbon into organic molecule
2. Reduction of that organic molecule
3. Regeneration of ribulose bisphosphate

Question 3

What is the equation for the fixation of carbon into an organic molecule

Answer 3

RuBP + CO2 —> 2 x 3-phosphglycerate

Question 4

What two molecules are required for the reduction of 3-phosphoglycerate

Answer 4

ATP and NADPH

Question 5

Which stage occurs twice per CBB cycle

Answer 5

Reduction of 3-phosphoglycerate

Question 6

Glyceraldehyde 3-phosphste is recycled into what first before RuBP

Answer 6

Ribulose 5-phosphate

Question 7

What is required to recycle ribulose 5-phosphate into RuBP

Answer 7

ATP (phosphate group added)

Question 8

Why does photrespirstion sometimes occur

Answer 8

Rubisco has some affinity for oxygen - imperfect shape

Question 9

Why was photrespirstion not a big problem when oxygenic photosynthesis evolved

Answer 9

Not much oxygen in the atmosphere

Question 10

Where does 2-phosphoglycate need to be transferred to in order to be converted back to 3-phosphglycerste

Answer 10

Mitochondria before back to chloroplast

Question 11

Why is photrespirstion wasteful

Answer 11

Requires ATP and prices waste CO2

Question 12

Above what point on a light response curve does excess light intensity occur

Answer 12

P max

Question 13

What is the effect of excess light energy in a plant

Answer 13

If not dissipated as heat then can knock electrons off molecules to produce free radical which can damage DNA

Question 14

In which field on a light response curve is photosynthesis most effective

Answer 14

Maximum quantum yield

Question 15

What process means photosynthesis does not occur below a certain light intensity

Answer 15

Respiration

Question 16

At what point on a light response curve does photosynthesis begin

Answer 16

Light compensation point

Question 17

How are shade leaves adapted to lower light intensities and fewer wavelengths (5 marks)

Answer 17

Larger leaves - absorb more light 
Thinner leaves 
More chlorophyll to increase absorption so darker leaves 
Less PSII as there is less sunlight
More LHCII to maximise absorption

Question 18

How are sun leaves (top of canopy) adapted to higher light inntensites (5 marks)

Answer 18

Smaller leaves - expensive to make leaves
Thicker leaves - cells stacked as sunlight can penetrate
Less chlorophyll so paler leaves
More PSII to use extra sunlight
Less LHCII as light harvesting achieved easily

Question 19

Why do sun leaves have a higher light compensation point than shade leaves

Answer 19

Not worth photosynthesising in low intensities of light

Question 20

How do plants acclimatise to their changing environment

Answer 20

Adjust components of the electron transport chain

Question 21

How do free radicals damage proteins lipids and DNA

Answer 21

By readily accepting electrons

Question 22

What condition do free radicals within plants lead to

Answer 22

Bleaching

Question 23

What two short term acclimation processes do plants use in high light intensites

Answer 23

Dissipate excess energy as heat - non-photochemical quenching (NPQ)
Stimulate the Xanthophyll cycle

Question 24

What medium term process do plants use in high light intensities

Answer 24

Increase photosynthetic capacity

Question 25

What long term, irriversible, acclimation process do plants use in high light intensities

Answer 25

Change morphology

Question 26

What is NPQ

Answer 26

Dissipation of heat energy

Question 27

What does the Xanthophyll cycle convert into what

Answer 27

Violaxanthin into zeaxanthin

Question 28

What functions as antioxidant to protect lipid membranes whilst stimulating NPQ

Answer 28

Zeaxanthin

Question 29

Why does increasing photosynthetic capacity take some time

Answer 29

Requires changes in gene expression