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APS 137 Plant Physiology > Lecture 3 - Calvin cycle > Flashcards

Lecture 3 - Calvin cycle Flashcards

1
Q

What prevents light independant reactions from always happening in the dark? [2]

A

They need ATP and NADPH

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2
Q

Basic function of Calvin cycle? [3]

A

Add CO2 to sugars to produce a 3-C sugar Phosphate requiring RuBisCO.

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3
Q

Whats Calvin Cycle reaction? [2]

A

C5+C1 -> 2x C3 3-phosphoglycerate

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4
Q

What is ‘phase 1’ of the Calvin Cycle? [1]

A

Fixation/assimilation.

Adding CO2 to 3-C molecule.

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5
Q

What is ‘phase 2’ of the Calvin Cycle? [4]

A

Reduction.

Adding e- to 3-phosphoglycerate, forming 1,3-bisphosphoglycerate.

Using an electron from ATP (which becomes ADP)

Then another e- to form
glyceraldehyde-3-phosphate.

Using an electron from NADPH (which becomes NADP+)

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6
Q

How many times does ‘phase 2’ of the Calvin Cycle happen?

A

Twice!

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7
Q

What is ‘phase 3’ of the Calvin Cycle? [3]

A

The regeneration of RuBP.

5 glyceraldehyde-3-phosphate -> 3RuBP.

In this reaction a molecule of ATP is formed as each RuBP has gained one phosphate.

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8
Q

What is RuBP? [1]

A

Ribulose, 1, 5-biphosphate.

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9
Q

The Calvin Cycle requires _ ATP and _ NADPH molecules. [2]

A

The Calvin Cycle requires 3 ATP and 2 NADPH molecules.

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10
Q

What is RuBisCO? [1]

A

Ribulose-1,5-bisphosphate carboxylase/oxygenase.

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11
Q

What does RubisCO do? [1]

A

It catalyses the carboxylation of RuBP.

It fixes CO2 into 3-phosphoglycerate and fixes O2 into 2-phosphoglycerate?

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12
Q

2-phosphoglycerate is a _____ product. [1]

A

2-phosphoglycerate is a waste product. [1]

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13
Q

What evolutionary conditions led to RubisCOs ‘wastefulness’? [1]

A

RuBisCO evolved in a low oxygen environment.

It evolved to take in CO2 in the simplest way, by grabbing one of the O molecules in CO2.

However it may also grab an O2 molecule.

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14
Q

What % of RuBisCO grabs are on O? [1]

A

25% of molecules used by RuBisCO are O2 :)

*In C3 plants

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15
Q

It takes _ ATP molecule to convert 2-phosphoglycerate to 3-phosphoglycerate. [1]

A

It takes 1 ATP molecule to convert 2-phosphoglycerate to 3-phosphoglycerate. [1]

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16
Q

What % of the planet do plants cover? [1]

A

40%.

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17
Q

How can light vary by latitude? [1]

A

There is less light away from the equator.

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18
Q

How can light vary by season? [1]

A

Because different seasons have different climate conditions.

19
Q

How can light vary in 24 hour cycles? [1]

A

Day and Night may vary!

20
Q

How can light vary on a ‘secondly’ basis? [1]

A

Plants may become shaded by clouds, animals etc.

21
Q

Give three limiting factors other than light which influence photosynthesis? [3]

A

Carbon Dioxide levels.

Water levels.

Nutrient levels.

22
Q

What is Maximum quantum yield? [1]

A

Maximum quantum yield is where photosynthesis increases in response to light intensity.

23
Q

What is the light compensation point? [1]

A

The point where C loss from respiration overtakes the amount assimilated by photosynthesis.

24
Q

How do shade leaves differ from typical leaves? [4]

A

They’re larger, thinner and have more chlorophyll.

25
Q

What does a pale leaf indicate? [1]

A

A lower amount of chlorophyll (relative to darker leaves).

26
Q

How does PSII differ in ‘sun leaves’? [1]

A

Sun leaves typically have more PSII, but there is a lower amount of LHCII within the photosystem.

More photosynthesis with less chlorophyll.

27
Q

How does PSII differ in ‘shade leaves’? [1]

A

There is less PSII but more LHCII within the photosystem.

28
Q

How does light-compensation point differ between shade and sun leaves? [1]

A

Shade leaves have a lower light-compensation point.

Less respiration, start gaining things from photosynthesis earlier.

29
Q

How do plants acclimate to different amounts of sunlight? [1]

A

They can adjust components of ETC (protein number).

30
Q

What’s the danger of too much light absorption? [2]

A

Chlorophyll absorbs light energy, but too much energy means there may not be enough reaction centres to send it too.

This excess energy can damage PSII in particular!

31
Q

What’s the issue with repairing PSII? [2]

A

It costs energy and it’s kinda inefficient.

If turnover is too quick it can even lead to photoinhibition, the stopping of photosynthesis.

32
Q

If chlorophyll absorb too much energy, the e_ _ _ _ _ _ _ _ _ e_ _ _ _ _ may be passed to _ _ _ _ _ _ which can create f_ _ _ r _ _ _ _ _ _ _ within the chloroplast and damage proteins, lipids and DNA due to them grabbing their e_ _ _ _ _ _ _ _. [6]

A

If chlorophyll absorb too much energy, the EXCITATION ENERGY may be passed to OXYGEN which can create FREE RADICALS within the chloroplast and damage proteins, lipids and DNA due to them grabbing their ELECTRONS.

33
Q

What is bleaching in regards to plants? [1]

A

Bleaching is crispy leaves due to chlorophyll death.

34
Q

How may a plant acclimate to prevent bleaching if it gets hit with a sudden light ray? [1]

A

A plant may dissipate excess energy as heat.

E.g. NPQ

35
Q

How may a plant increase photosynthetic capacity? [2]

A

A plant may make more PSII and electron transport proteins.

36
Q

How may developing plants and leaves acclimate to different levels of light? [1]

A

Individual leaves may differentiate to look more sun or shade adapted.

37
Q

When does non-photochemical quenching occur? [1]

A

NPQ occurs when photosynthetic proteins absorb excess electron energy and dissipate it as heat.

38
Q

What are Xanthophylls? [1]

A

Pigment molecules, like chloroplasts but tend to be red and yellow!

39
Q

What are the two types of Xanthophyll? [2]

A

Violaxanthin.

Zeaxanthin.

‘Two components of the xanthophyll cycle’

40
Q

When is violaxanthin released? [1]

A

When there’s no light stress.

41
Q

When is zeaxanthin released? [1]

A

When there’s light stress.

42
Q

What two functions does zeaxanthin have? [2]

A

It may act as an anti-oxidant which specifically protects lipid membranes.

It can act as a regulatory molecule, stimulating NPQ which leads to more heat dissipation.

This process is a little inefficient though.

43
Q

How long does it take for a plant to permanently change its photosynthetic capacity and how does it do this? [2]

A

Around a week.

It’s caused by changes in gene and protein expression.

E.g. Increasing genes for making sugars and extra bits of ETC.

APS 137 Plant Physiology (19 decks)

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