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Bioc 405 > Calvin Cycle and PPP > Flashcards

Calvin Cycle and PPP Flashcards

1
Q

where is CO2 fixed to and by what?

A

RuBisCO attaches a CO2 to ribulose 1,5-bisphosphate (RuBP) turning gas into a carbohydrate

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2
Q

After Rubisco carboxylates RuBP, what is the transient 6C intermediate split into, and how many?

A

Into two 3-phosphoglycerates

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3
Q

What does the active site of rubisco utilize to attach CO2 to RuBP

A

A carbamylated lysine residue and a Mg2+

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4
Q

Why is RuBisCO slow? (more than accidently binding O2)

A

Stabilization of the late transition state to differentiate between O2 and CO2 creates a sort of product inhibition, so releasing the product and completing the reaction

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5
Q

What is the reverse reactions of steps 6&7 of glycolysis?

A

Reduction of 3PG to GAP

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6
Q

What drives the reduction from 1,3-bisphophoglycerate to glyceraldehyde-3-phosphate?

A

Cleavage of the acyl-phosphate bond

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7
Q

How many CO2s go through the cycle to make 6 GAP?

A

3

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8
Q

Where do the majority of GAPs go to in the cycle, and how many? Where does the rest go to, and how many?

A

5 are used to regenerate 3 RuBP. 1 goes to net carbohydrate synthesis

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9
Q

For each 3 turns you start with __ carbons from __ RuBPs, add in __ C from __ CO2s, and siphon off __ carbons in __ GAP to make sugars

A

For each 3 turns you start with 15 carbons from 3 RuBPs, add in 3 C from 3 CO2s and siphon off 3 C in 1 GAP to make sugar

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10
Q

Which two enzymes change the number of carbons in the calvin cycle?

A

aldolase and transketolase

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11
Q

Which two enzymes move things around within the molecule in the calvin cycle?

A

isomerases and epimerases

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12
Q

What happen between GAP and DHAP and which enzyme does this?

A

isomerized by TIM

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13
Q

What combines one 3C aldose and one 3C ketose into a 6C carbohydrate?

A

aldolase

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14
Q

What enzyme transfers 2C from a ketose to an aldose acceptor?

A

transketolase

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15
Q

What cofactor is part of transketolase

A

TPP

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16
Q

What enzyme adds a 3C DHAP to the 4C E4P to make the 7C SBP

A

aldolase

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17
Q

What enzyme transfers 2C from S7P to GAP to make two 5C molecules

A

transketolase

18
Q

What are R5P and Yu5P converted to and how many?

A

3 RuBPs

19
Q

What enzyme converts R5P?

A

(ribose phosphate) isomerase

20
Q

What enzyme converts Xu5P?

A

(phosphopentose) epimerase

21
Q

What is the delta C for aldolases? for transketolases?

A

3 for aldolase, 2 for transketolase

22
Q

What are the regulated steps in the calvin cycle?

A

rubisco and the kinase/phosphatases

23
Q

Is biophosphatase reduced or oxidized to become active?

A

reduced

24
Q

What reduces biophosphatase?

A

Thioredoxin

25
Q

How many ATPs and NADPHs does the calvin cycle burn?

A

9 ATPs and 6 NADPHs

26
Q

2 GAPs from 2 turns of the calvin cycle are used to make what?

A

hexoses

27
Q

Where is sucrose formed?

A

cytoplasm

28
Q

Is sucrose a long term or short term energy storage?

A

short term

29
Q

Where is amylose formed?

A

stroma

30
Q

Is amylose a long term or short term energy storage?

A

long term

31
Q

What is the pentose phosphate pathway?

A

oxidation of glucose in the cytosol

32
Q

Where does the PPP occur?

A

everywhere but especially in anabolic tissue like the liver and adipose tissue

33
Q

How many NADHs does the first stage of the PPP produce?

A

2

34
Q

During the first stage of the PPP which substrate has 2 carbons oxidized to generate the 5C sugar Ru5P?

A

glucose-6-phosphate

35
Q

What are two key enzymes that move carbons around in the PPP?

A

transketolase and transaldolase

36
Q

What does stage 2 convert 3 Ru5Ps to in the PPP?

A

2 F6Ps and 1 GAP

37
Q

What cofactor does transaldolase use to transfer 3C from a ketose onto an aldose?

A

no cofactor- reaction is catalyzed by a lysine side chain that forms a schiff base

38
Q

What is the difference between aldolases and transaldolases?

A

aldolase sticks a proton onto the carbanion intermediate, while transaldolase sticks an aldose on

39
Q

What is an important use of NADPH

A

protects cell from oxidative damage through reduction of glutathione

40
Q

Which pathway is the main source of cytoplasmic NADPH in eukaryotes?

A

PPP

Bioc 405 (15 decks)

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