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Biochemistry > Biochem Exam 3: Citric Acid > Flashcards

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
Q

Kinase does what to the PDH?

A

Phosphorylates it

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26
Q

Phosphatase does what to the PDH complex?

A

Dephosphorylates

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27
Q

What is the link btw glycolysis and the citric acid cycle?

A

PDH

28
Q

What is the first step in the TCA cycle ?

A

Condensation of 4 carbon oxaloacetate and 2 carbon acetyl group

29
Q

What catalyzes the first step of the TCA cycle?

A

Citrate synthase

30
Q

What is the 2nd step of the TCA cycle?

A

Move hydroxal group on citrate via dehydration

31
Q

What enzyme helps to move the hydroxl group of citrate?

A

Aconitase

32
Q

What do we do for step three of the TCA cycle?

A

Take isocitatre to alpha ketoglutarate via an oxidation-reduction reaction

33
Q

T/F

Isocitrate to alpha-ketoglutarate is the rate limiting step

A

True

34
Q

What enzyme helps us move from isocitrate to alpha-ketoglutarate?

A

Isocitrate dehydrogenase

35
Q

What is alpha-ketoglutarate dehydrogenase similar to?

A

Pyruvate dehydrogenase

36
Q

What do pyruvate and alpha-ketoglutarate have in common?

A

Both reactions decarboxylation an alpha-ketoacids and create a thioester linkage with CoA

37
Q

Succinylcholine CoA to succinate directly yields what compound?

A

GTP, ATP

38
Q

What tissue normally produces GTP instead of ATP when in the TCA cycle?

A

Liver

39
Q

What tissue normally produces ATP instead of GTP when going through the TCA cycle?

A

Muscles & heart

40
Q

What enzyme helps to moves succinyl CoA to succinate?

A

Succinyl CoA synthetase

41
Q

Where is succinate dehydrogenase located?

A

Inner mitochondrial membrane

42
Q

What does succinate dehydrogenase generate?

A

FADH2

43
Q

Succinate goes to ?

A

Fumarate

44
Q

What enzyme helps succinate go to fumarate?

A

Succinate dehydrogenase

45
Q

which complex of the electron transport chain is directly associated with succinate dehydrogenase?

A

Complex II

46
Q

Fumarate goes to __________ in the TCA cycle

A

Malate

47
Q

What enzyme catalyzes the reaction of fumarate to malate?

A

Fumarase

48
Q

When changing fumarate to malate, what type of malate is formed?

A

L-Malate

49
Q

Malate goes to ______________ in the TCA cycle

A

Oxaloacetate

50
Q

What enzyme catalyzes the change of malate to oxaloacetate

A

Malate dehydrogenase

51
Q

What are two molecules that drive malate to transition into oxaloacetate?

A

The use of oxaloacetate & NADH

52
Q

In the PDH complex what effect does ca2+ have ?

A

It increase phosphatase which dephosphoralates the PDH and increases its activity of pushing acetyl CoA into the citric acid cycle

53
Q

When working out strenuously, what likely happening to the PDH?

A

It is being stimulated

54
Q

T/F

Insulin can stimulate fatty acid synthesis

A

True

55
Q

How can insulin stimulate fatty acid synthesis?

A

Activating phosphatase and increasing the conversion of pyruvate to acetyl CoA

56
Q

Where are the three points of regulation in the TCA cycle?

A
  1. Pyruvate to acetyl CoA
  2. Isocitrate to alpha ketoglutarate
  3. Alpha ketoglutarate to succinyl CoA
57
Q

What type of reaction yields citrate from oxaloacetate?

A

Condensation

58
Q

What can an alpha ketoglutarate that builds up from enzyme inhibition be used for?

A

Synthesis of amino acids and purine bases

59
Q

What does Anaplerotic mean?

A

Reactions that form intermediates in other metabolic pathways

60
Q

T/F

TCA cycle is anaplerotic

A

True

61
Q

What are two major anaplerotic reactions?

A
  1. Degradation of amino acids

2. Carboxylation of pyruvate

62
Q

Citrate can be used in what other metabolic pathways?

A

Fatty acids, sterols

63
Q

Alpha glutarate can be used in what other metabolic pathways?

A

Glutamate —> amino acids —> purines

64
Q

Succinyl CoA can be used in what other metabolic pathways?

A

Porphyria, heme, chlorophyll

65
Q

Oxaloacetate can be used in what other metabolic pathways?

A

Asparatate—> amino acids, purine, pyrimidines

Glucose

66
Q

When are anaplerotic reactions required?

A

During state of low energy

Biochemistry (9 decks)

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