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Exam 4 Flashcards

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1
Q

Under aerobic conditions what does pyruvate do?

A

Pyruvate enters the mitochondria where it is then converted into acetyl CoA

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2
Q

What are the two fates acetyl CoA has?

A

TCA cycle or lipogenesis

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3
Q

is the formation of acetyl CoA reversible?

A

No

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4
Q

what does acetyl CoA in the citric acid cycle form?

A
  • a 2 carbon acetyl unit
  • high electron carriers that can be used to make ATP
  • 2 molecules of carbon dioxide
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5
Q

What oxitatively decarboxylates pyruvate to form acetyl CoA

A

pyruvate dehydrogenase complex

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6
Q

what is the net reaction for the formation of acetyl CoA

A

pyruvate + CoA + NAD+ —> acetyl CoA + CO2 + NADH + H+

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7
Q

What are the three enzymes present in the pyruvate dehydrogenase complex?

A
  1. pyruvate dehydrogenase component (E1)
  2. dihydrolipoyl transacetylase (E2)
  3. dihydrolipoyl dehydrogenase (E3)
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8
Q

what is the prosthetic group for pyruvate dehydrogenase component

A

TPP

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9
Q

What is the prosthetic group for dihydtolipoyl transacetylase?

A

Lipoamide

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10
Q

what is the prosthetic group for Dihydrolipoyl dehydrogenase?

A

FAD

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11
Q

What coenzyme does Thiamine B1 create

A

thiamine pyrophosphate

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12
Q

what coenzyme does riboflavin B2 make

A

FAD

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13
Q

What coenzyme does Nicontinic acid (niacin, B3) make

A

NAD+

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14
Q

What coenzyme does panthothenic acid (B5) make

A

coenzyme A

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15
Q

what are the 3 steps involved in the synthesis of acetyl CoA from pyruvate?

A
  1. decarboxylation
  2. oxidation
  3. acyl transfer to CoA
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16
Q

What are the 5 required coenzymes in the sysnthesis of acetyl CoA

A
  1. Thiamine pyrophosphate (TPP)
  2. lipoic acid
  3. FAD
  4. NAD+
  5. coenzyme A
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17
Q
A
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17
Q

What is step two Oxidation?

A

the hydroxethyl attached to the TPP is oxidized to an acetylene group which is transferred to lipoamide catalyzed by E1 this reaction yield acetyl- lipoamide

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17
Q

What is step one decarboxylation?

A

Pyruvate dehydrogenase (E1) catalyzes the decarboxylation, pyruvate combines with the ionzied form of coenzyme TPP

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18
Q

How is lipoamide formed

A

by the attachment of the lipotic acid to a lysine residue in E2 (dihydrolipoyl transacetylase

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19
Q

What is step 3 (formation of acetyl CoA)

A

E2 catalyzes the transfer of the acetyl group from the acetyl-lipoamide to coenzyme A to form acetyl CoA. This creates a thioester bond which holds alot of energy that can be used for work later

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20
Q

What is step 4 ( dihydrolipoamid dehydrogenase)? What is the prosthetic group? what is the mobile electron carrier ?

A

-dihydrolipoamide must be reoxidized this is catalyzed by dihydroplipoamide dehydrogenase (E3)
-FADH2 is the prosthetic group
-NAD+ is the mobile electron acceptor

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21
Q

What allows for the rapid movement of substrates and products from the active site of one complex to another

A

the lipoamide arm

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22
Q

What allosterically inhibits E2

A

acetyl CoA

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23
What allosterically inhibits E3
NADH
24
What covalent modification inhibits E1
kinase with the complex that phosphorylates and inactivates E1
25
What covalent modification activates E1
Phosphatase associated with the complex that removes the phosphate and activates the enzyme
26
what is step on of the citric acid cycle?
Citrate synthase catalyzes the condensation of acetyl CoA and oxaloacetate to for citrate
27
What is a synthase?
An enzyme that catalyzes the reaction in which 2 units are joined without the direct participation of ATP
28
What type of fit does citrate synthase exhibit?
It exhibits induced fit oxaloacetate binding by citrate synthase and induces structural changes that lead to the formation of the acetyl CoA binding site the formation of the citryl CoA intermediate causes a structural change that completes the active site formation.
29
What is step 2 of the citric acid cycle
Aconitase (lyase) catalyzes the formation of isocitrate from citrate
30
What is step 3 of the citric acid cycle?
-it is the 1st of 4 oxidation-reduction reactions - 6 carbons to 5 carbons - isocitrate dehydrogenase catalyzes the oxidative decarboxylation of isocitrate forming alpha-ketoglutarate high energy electrons as NADH
31
What is step 4 of the citric acid cycle
- 2nd oxidation-reduction reaction - 5 carbons to 4 carobons - alpha-ketoglutarate dehydrogenase complex catalyzes the synthesis of succinylcholine coA from a-ketoglutarate, generating NADH
32
What is step 5 of the citric acid cycle?
- begins stage 2 - a compound with high phosphorylation transfer potential is generated from succinyl coenzyme A succinyl synthesis catalyzes the cleavage of a thioester linkage forming succinate and ATP (the only ATP made in the Citric acid cycle )
33
What is step 6 of the citric acid cycle
Succinate dehydrogenase is embedded in the inner mitochondrial membrane it part ETC complex II 3r redox reaction and generates FADH2
34
What is step 7 of the citric acid cycle?
Fumarase hydrates fumarate and forms malate
35
What are the protein pumping complexes?
NADH-Q oxioreductase (complex 1) Q-cytochrome C oxioreductase ( complex 3) Cytochrome C oxidase (complex 4)
36
What is complex 2 and what does it do?
complex 2 is succinate-Q-reductase is delivers electrons from FADH2 to complex 3 by ubiquinone
37
What happens in compex one?
- in complex one the electrons from NADH are passed along from Q to form QH2. 4 protons are pumped out of the mitochondria by complex one while the other two are tied up by the QH2 molecule - this contributes to the proton motive force
38
What happens in complex 2
The FADH2 generated in the citric acid cycle reduce Q to QH2 and enters the Q pool NOT A PROTON PUMP
39
What happens in complex 3
The elctron from QH2 are used to reduce 2 molecules of cytochrome c this is catalyzed by Q-cytochrome c oxioreductase - this step is called the Q cycle - needs two cytochrome C since cytochrome C can only carry one electron
40
What is formed in complex 3
- 4 protons are pumped out of the mitochondira and 2 are removed from the matrix by QH2 the 2 molecules of QH2 create 2 reduced cytochrome C molecules and one new molecule of QH2
41
What happens in complex 4
cytochrome c oxiase accepts 4 electrons from 4 molecules of cytochrome c in order to catalyze the reduction of O2 into two molecules of water
42
In the cytochrome c oxidase reaction how many protons are removed from the matrix
8 - 4 chemical protons are used to reduce oxygen - 4 are pumped into the intermembrane space
43
What makes up the complex called respirasome?
two copies of complex 1,3, and 4
44
What are the electron carriers in the electron transport chain?
– flavin mononucleotide (FMN) – iron associated with sulfur in proteins (iron–sulfur (Fe-S) proteins) – iron incorporated into hemes that are embedded in proteins called cytochromes – a mobile electron carrier called coenzyme Q (Q, ubiquinone, CoQ10).
45
What can citrate leave the TCA cycle to form?
Fatty acids and sterols
46
What can alpha ketoglutarate leave the TCA cycle to form
purines
47
What can succinyl CoA leave the TCA cycle to form
porphyrins, heme, and chlorophyll
48
What can oxaloacetate leave the TCA cycle to form
amino acids, purine, pyrimidines, and glucose
49
What is the mechanism for Aconitase
1. citrate enters active cite 2. his-101 donates proton of hydroxyl c3 3. ser-642 accept proton from c2 creating double bond between c2 and c3 4. cis-aconitase flips 180 degrees 5. his 101 attracts proton from water to perform nucleophillic attack on c2 6. protanated set-642 donates proton back to c3
50
What is the proton gradient generated by the oxidation of NADH and FADH2 called?
Proton motive force
51
What does the proton motive force generate?
chemical gradient and a charge gradient
52
What happens when ATP synthase binds to one another?
it forms a dimer and contributes to the formation of the cristae the dimers also oligomerize for additional stability
53
What are the mobile units of the ATP synthase pump?
c,Y, and E
54
What make up the F0 subunit?
a,b
55
What makes up the F1 subunit?
alpha, beta, delta
56
What are the 3 forms the catalytic B subunits of the F1 component exist in?
open (O), Loose (L), and Tight (T)
57
Can multiple B subunits be in the same form at the same time
No
58
What determines the number of protons required to synthesize a molecule of ATP
The number of C subunits
59
Explain the glycerol phosphate shuttle?
in muscle electrons from the cytoplasmic NADH enter the ETC by using the glycerol phosphate shuttle the electron are there transferred from NADH to FADH2 and to Q to form QH2
60
Explain the malate aspartate shuttle?
in the heart and liver electrons from cytomplasmic NADH are used to generate mitochondrial NADH through the malate aspartate shuttle
61
What does the ATP-ADP translocase enable?
the exchange of cytoplasmic ADP for mitochondrial ATP it is powered by the proton-motive force
62
What does the complete oxidation of glucose yield?
30 ATP
63
What must be present for ATP synthase to be active?
ADP

biochem (5 decks)

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