Carbon Fixation Flashcards

1
Q

Carbon fixation is a ___ reaction.

A

Dark

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2
Q

Function of Carbon Fixation

A

Use NADPH and ATP to fix carbon dioxide and make glyceraldehyde-3-phosphate

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3
Q

Stage 1

A

Carbon fixation

CO2 fixation catalyzed by the enzyme Rubsico

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4
Q

Product of Stage 1

A

3-phosphoglycerate

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5
Q

Most abundant protein in humans

A

Collagen

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6
Q

Most abundant protein in plants

A

Rubisco

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7
Q

Rubisco

A

Ribulose 1,5-bisphosphate carboxylase-oxygenase

Has 16 subunits (8 large & 8 small)

Less efficient enzyme

kcat (turnover #) ≈ 3 s-1

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8
Q

Stage 2

A

Reduction

Glyceraldehyde-3-phosphate (G-3-P) is the main product of Calvin cycle

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9
Q

Stage 3

A

Regeneration of acceptor

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10
Q

What enzymes are regulatory enzymes?

A

Phosphoribulokinase
Ribulose bisphosphate carboxylase
Fructose bisphosphatase
Sedoheptulose bisphosphatase

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11
Q

High Km

A

Can take more substrate

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12
Q

Low Km

A

Saturated at low levels of substrate

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13
Q

The Calvin Cycle occurs in the ____

A

Stroma

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14
Q

Conditions that increase activity of Rubisco

A

Light
Higher Mg2+ concentration
Higher pH

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15
Q

What enzyme activates Rubsico?

A

Rubisco activase

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16
Q

Rubsico is ____ at night

A

Inactive

17
Q

Rubisco is inhibited by:

A

CA1P (2-carboxyarabinitol-1-phosphate), which is produced in the dark

18
Q

Four Calvin cycle enzymes and Rubsico activate are regulated by _____

A

Light-dependent reduced ferredoxin

19
Q

Rubisco, which fixes CO2, also reacts with ____ to produce a metabolically useless product

A

O2

20
Q

What is the product of a reaction between Rubsico and O2?

A

2-phosphoglycolate

21
Q

Salvaging 2-phosphoglycolate is costly. This pathway is called _____

A

Photorespiration

22
Q

In C4 plants (corn), CO2 fixation and Rubisco activity are _____

A

Spatially separated

23
Q

CAM (Crassulacean Acid Metabolism) plants are adopted to drought

A

Acidity of vacuole builds up at night as reaction proceeds

Dark: Stomata open
Light: Stomata closed