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BS129: Physiology, Neurobiology and Metabolism > Lecture 12. Photosynthesis > Flashcards

Lecture 12. Photosynthesis Flashcards

1
Q

Where does all free energy needed by biological systems come from?

A

Solar energy trapped by photosynthesis

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2
Q

What is the function of the stomata and how do they function?

A

The stomata can open and close to allow exchange of air

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3
Q

What reactions are involved in energy capture?

A

Light dependent reactions

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4
Q

What reactions are involved in energy expenditure?

A

Light independent reactions

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5
Q

What are the aims of the light dependent reactions?

A

The capture of photons
The conversion of light energy to ATP and NADPH

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6
Q

What are the aims of the light independent reactions?

A

Fixing or capturing of CO₂
Making bigger molecules that can be moved round the plant or be stored

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7
Q

What is the energy of a photon dependent on?

A

Its wavelength

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8
Q

What is chlorophyll?

A

A Mg²⁺ porphyrin that contains phytol, highly hydrophobic

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9
Q

When illuminated, what do isolated chloroplasts do?

A

Evolve O₂
Reduce an electron acceptor (e.g ferricyanide)

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10
Q

Why was the Hill reaction crucial?

A

It showed that the primary event in photosynthesis is the light-driven energy requiring transfer of an electron from one substance to another

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11
Q

What do photons do to electrons?

A

Cause electrons to go from ground state to excited state
The excited state can be transferred until captured in reaction centre

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12
Q

Where are the reaction centres in plants?

A

Chlorophylls - where chemical reactions happen

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13
Q

What are the names of the two reaction centres?

A

Photosystem I and II

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14
Q

What is photosystem II also known as?

A

P680, water-plastoquinone oxidoreductase

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15
Q

What makes the enzyme in PSII special?

A

Water-plastoquinone is the only natural enzyme that splits water

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16
Q

How many electrons does water need to donate to make one molecule of oxygen?

A

4

17
Q

How many protons are released into the lumen in PSII?

A

4

18
Q

Where do the electrons from PSII go next?

A

Plastoquinone

19
Q

Where do the electrons from plastoquinone get transferred to?

A

Cytochrome bf complex

20
Q

How many protons are pumped into the lumen by the cytochrome bf complex?

A

2

21
Q

Where do the electrons from cytochrome bf complex go next?

A

Plastocyanine

22
Q

What is photosystem I also known as?

A

P700, plastocyanin ferredoxin oxidoreductase

23
Q

Where do electrons traveling into PSI come from?

A

Plastocyanine

24
Q

Where do the electrons from PSI go next?

A

Ferredoxin

25
Q

What is the final electron acceptor?

A

NADP⁺

26
Q

What happens in the Calvin cycle?

A

CO₂ is fixated into sugars
CO₂ + 4H⁺ + 4e⁻ → CH₂O + H₂O

27
Q

What is the first product of the Calvin cycle?

A

3-phosphoglycerate

28
Q

What catalyses carbon fixation?

A

RuBisCo

29
Q

Steps in the Calvin cycle

A
  1. Carbon fixation
  2. Reduction of 3PG to Glyceraldehyde-3-phosphate (G-3-P)
  3. Regeneration of starting molecule: RuBP (Reverse of PPP)
30
Q

Calvin cycle balanced equation

A

6CO₂ + 18ATP + 12NADPH + 12H₂O → C₆H₁₂O₆ + 18ADP + 18Pi + 12NADP⁺ + 6H⁺

31
Q

Why does RuBisCo suck big dodongo dick?

A

Slow catalytic activity: about 3 reactions per second
Isn’t good at distinguishing between O₂ and CO₂
Reaction with oxygen wasteful - costs ATP to lose CO₂

32
Q

When does more photorespiration occur?

A

At hotter temperatures

33
Q

What are two ways that some plants have evolved to concentrate CO₂ at the site of the Calvin cycle?

A

Mesophyll cells capture CO₂
Bundle cells cary out Calvin cycle

34
Q

What is the mobile energy storage molecule in plants?

A

Sucrose

35
Q

What is the main energy storage molecule in plants?

A

Starch

36
Q

Where is starch found?

A

In stroma in chloroplasts
In seeds and tubers like potatoes

37
Q

What is starch a mixture of?

A

Amylose and amylopectin

BS129: Physiology, Neurobiology and Metabolism (34 decks)

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