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Biology - Eukaryotes > Biochemistry - Photosynthesis > Flashcards

Biochemistry - Photosynthesis Flashcards

1
Q

What type of reaction is photosynthesis?

A

Endergonic, using photon light energy

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2
Q

What are the two seperate reactions of photosynthesis?

A

Dark and Light reactions

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3
Q

Dark reactions

A

Utilise NADPH and ATP generated by light-dependent electron transport

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4
Q

Where does Dark reaction occur?

A

Chloroplast storma

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5
Q

Where is CO2 uptake mediated?

A

Stomata in the lower epidermis

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6
Q

What is stomata size regulated by?

A

Guard cells

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7
Q

What is the structure of chloroplasts?

A

Two membranes enclosing thestroma, containing thylakoid where PS takes place

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8
Q

Overview of the light reactions

A

Transfer of electrons from water to NADP forming NADPH, coupled with proton transfer and subsequent ADP phosphorylation

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9
Q

Overview of the Calvin Cycle

A

ATP and NADHP convert CO2 into carbohydrates, regenrating NADH and ADP

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10
Q

Photosystem II

A

A membrane supercomplex, capturing sunlight catalysing water oxidation

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11
Q

First step in light reactions?

A

Photosystem II splitting water

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12
Q

What does PSII reduce?

A

Plastoquinone to Plastoquinol

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13
Q

Plastoquinol

A

The primary electron carrier in plants.

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14
Q

What does plastoquinol do after reduction?

A

Carrier electrons to cytochrome b6f

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15
Q

Cytochrome b6f

A

Oxidises plastoquinol to plastoquinone, whilst reducing plastocyanin

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16
Q

Plastocyanin

A

A redox protein in photosyntehsis carrying electrons from cytochrome b6f to photosystem i

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17
Q

What does PS I do?

A

Oxidise plastocyanin forming ferredoxin

18
Q

What happens after ferredoxin is formed?

A

Used by ferredoxin-NADP reductase enzyme to reduce NADP to NADPH

19
Q

Exergonic process in terms of electron transfer?

A

Electrons transferred from low redox potential, good reductants to high potential good oxidants.

20
Q

What allows chain acceptors to be reduced?

A

Light excitation of chlorophyll

21
Q

What is oxidised chlorophull reduced by?

A

Water and plastocyanin

22
Q

What does oxidised chlorophyll result in?

A

Proton concentration between stroma and lumen changes, build up in lumen

23
Q

Why is stroma-lumen proton concentration important?

A

Allows photophosphorylation to occur, this being the basis for driving ATP synthase

24
Q

Whatpower ADP-Pi synthesis in ATP synthase?

A

Proton moving down concentration gradient, which is exergonic

25
Q

What light does chrlophyll and carotenoid absorb respectively?

A

Red and Blue thus are green, and blue, thus appearing yellow/red/orange

26
Q

What is each light quanta calculated by?

A

Plancks constant multiplied by frequency of radiation.

27
Q

Wavelenghts of blue and red photons respectively?

A

450 and 650nm

28
Q

How is wavelength calculated?

A

Velocity x Frequency

29
Q

What does E=hc/lambda describe

A

Energy of a particular wavelength of light

30
Q

How does chlorphyll structure permit light absorption?

A

Electrons jump from ground state to (1or2) excited state, where to 1 required ed photon and 2 require blue

31
Q

Internal Conversion

A

A non-radioactive decay process where an excited nuclei electromagnetically interacts with a surrounding orbital electron.

32
Q

When does internal conversion occur?

A

Excited second state electrons through vibrations emit heat as energy, demoting to the first state

33
Q

What happens to the electron in the first state?

A

Lost as heat, return to ground state or excitation energy transfer if another chlorophyll is nearby.

34
Q

What mediates EET from pigments to LHC?

A

Non-covalent binding

35
Q

How does protein structure allow for electron funneling?

A

The 1 and 2 energy levels are shifted based on protein structure with respect to neighbouring pigments

36
Q

General structure of light harvesting complexes?

A

Reaction centre where primary chlorophyll reside, opposed to other pigments responsible for shuttling and concentrating excitating energy.

37
Q

How does PSII function?

A

Excites two P680 chlorophylls, which undergo charge seperation, resulting in lower redox potential

38
Q

How does P680 achieve four charge seperations for H2O seperation?

A

Manganese transistion metals multiple oxidation states accumulate postivei charges by P680 oxidation which drives water breakdown.

39
Q

What does p680 mediated water breakdown result in?

A

Regeneration of original state of the element and release of proton into lumen.

40
Q

What happes when PSI reduces ferredoxin?

A

It can generate NADPH in the calvin cycle

41
Q
A

Biology - Eukaryotes (13 decks)

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