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Biochem Exam 3: Citric Acid Flashcards

1
Q

Where does the citric acid cycle take place?

A

Inside mitochondria

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2
Q

T/F

Citric acid cycle is amphibolic

A

True (anabolism & catabolism)

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3
Q

What are other names for the citric acid cycle?

A
  1. TCA (tricarboxylic acid cycle)

2. Kreb cycle

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4
Q

Oxidation of 2-carbon units produces:

A

2 CO2 molecules
1 GTP
NADH
FADH2

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5
Q

What is the carbon source for the citric acid cycle?

A

Acetyl CoA

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6
Q

Where is acetyl CoA created?

A

From pyruvate

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7
Q

Where is the high energy bond in acetyl CoA

A

Between the sulfur and the acetyl CoA

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8
Q

What is the active form of acetate?

A

Acetyl CoA

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9
Q

What are 2 energy molecules we can make acetyl CoA from?

A

Lipids
Glucose
Proteins

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10
Q

What are the three steps to take pyruvate to acetyl CoA?

A
  1. Decarboxylation (create CO2)
  2. Oxidation
  3. Transfer CoA (create NADH)
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11
Q

How does pyruvate enter the mitochondria?

A

Mitochondrial pyruvate carrier (MPC)

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12
Q

What catalyzes the decarboxylation of pyruvate?

A

PDC (pyruvate dehydrogenase complex)

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13
Q

PDC is made of how many enzymes?

A

3
E1
E2
E3

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14
Q

How many coenzymes are used in pyruvate dehydrogenase reaction?

A

5

  1. Thiamine pyrophosphate (TTP)
  2. Lipoid acid
  3. FAD
  4. COA
  5. NAD
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15
Q

What coenzymes are catalytic?

A

TPP
Lipoid acid
FAD

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16
Q

What coenzymes are stoichiometric cofactors?

A

CoA

NAD

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17
Q

How many copies of E1 & E2?

A

24

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18
Q

How many copies of E3?

A

12

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19
Q

Which enzyme is the flexible arm in the PDH (PDC)

A

E2 bc it contains lipomide

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20
Q

Which enzymatic domain has lipomide in PDH?

A

E2

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21
Q

How is the PDH regulated?

A

Allosteric interactions

Reverse phosphorylation

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22
Q

What does high acetyl CoA do to the PDH?

A

Directly inhibits E2

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23
Q

T/F

When PDH is phosphorylated it is inactive

A

True

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24
Q

T/F

When PDH is not phosphorylated is is active

A

True

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25
Kinase does what to the PDH?
Phosphorylates it
26
Phosphatase does what to the PDH complex?
Dephosphorylates
27
What is the link btw glycolysis and the citric acid cycle?
PDH
28
What is the first step in the TCA cycle ?
Condensation of 4 carbon oxaloacetate and 2 carbon acetyl group
29
What catalyzes the first step of the TCA cycle?
Citrate synthase
30
What is the 2nd step of the TCA cycle?
Move hydroxal group on citrate via dehydration
31
What enzyme helps to move the hydroxl group of citrate?
Aconitase
32
What do we do for step three of the TCA cycle?
Take isocitatre to alpha ketoglutarate via an oxidation-reduction reaction
33
T/F | Isocitrate to alpha-ketoglutarate is the rate limiting step
True
34
What enzyme helps us move from isocitrate to alpha-ketoglutarate?
Isocitrate dehydrogenase
35
What is alpha-ketoglutarate dehydrogenase similar to?
Pyruvate dehydrogenase
36
What do pyruvate and alpha-ketoglutarate have in common?
Both reactions decarboxylation an alpha-ketoacids and create a thioester linkage with CoA
37
Succinylcholine CoA to succinate directly yields what compound?
GTP, ATP
38
What tissue normally produces GTP instead of ATP when in the TCA cycle?
Liver
39
What tissue normally produces ATP instead of GTP when going through the TCA cycle?
Muscles & heart
40
What enzyme helps to moves succinyl CoA to succinate?
Succinyl CoA synthetase
41
Where is succinate dehydrogenase located?
Inner mitochondrial membrane
42
What does succinate dehydrogenase generate?
FADH2
43
Succinate goes to ?
Fumarate
44
What enzyme helps succinate go to fumarate?
Succinate dehydrogenase
45
which complex of the electron transport chain is directly associated with succinate dehydrogenase?
Complex II
46
Fumarate goes to __________ in the TCA cycle
Malate
47
What enzyme catalyzes the reaction of fumarate to malate?
Fumarase
48
When changing fumarate to malate, what type of malate is formed?
L-Malate
49
Malate goes to ______________ in the TCA cycle
Oxaloacetate
50
What enzyme catalyzes the change of malate to oxaloacetate
Malate dehydrogenase
51
What are two molecules that drive malate to transition into oxaloacetate?
The use of oxaloacetate & NADH
52
In the PDH complex what effect does ca2+ have ?
It increase phosphatase which dephosphoralates the PDH and increases its activity of pushing acetyl CoA into the citric acid cycle
53
When working out strenuously, what likely happening to the PDH?
It is being stimulated
54
T/F | Insulin can stimulate fatty acid synthesis
True
55
How can insulin stimulate fatty acid synthesis?
Activating phosphatase and increasing the conversion of pyruvate to acetyl CoA
56
Where are the three points of regulation in the TCA cycle?
1. Pyruvate to acetyl CoA 2. Isocitrate to alpha ketoglutarate 3. Alpha ketoglutarate to succinyl CoA
57
What type of reaction yields citrate from oxaloacetate?
Condensation
58
What can an alpha ketoglutarate that builds up from enzyme inhibition be used for?
Synthesis of amino acids and purine bases
59
What does Anaplerotic mean?
Reactions that form intermediates in other metabolic pathways
60
T/F | TCA cycle is anaplerotic
True
61
What are two major anaplerotic reactions?
1. Degradation of amino acids | 2. Carboxylation of pyruvate
62
Citrate can be used in what other metabolic pathways?
Fatty acids, sterols
63
Alpha glutarate can be used in what other metabolic pathways?
Glutamate —> amino acids —> purines
64
Succinyl CoA can be used in what other metabolic pathways?
Porphyria, heme, chlorophyll
65
Oxaloacetate can be used in what other metabolic pathways?
Asparatate—> amino acids, purine, pyrimidines | Glucose
66
When are anaplerotic reactions required?
During state of low energy

Biochemistry (9 decks)

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