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Block 3 Week 1 Meg > Valencik: Carbohydrate metabolism II > Flashcards

Valencik: Carbohydrate metabolism II Flashcards

1
Q

Pyruvate has four fates: Through transamination, it can generate what?

A

alanine

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2
Q

Pyruvate has four fates: Through carboxylation, it can generate what?

A

OAA

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3
Q

Pyruvate has four fates: Through oxidative decarboxylation, it can generate what?

A

Acetyl-CoA

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4
Q

Pyruvate has four fates: Through reduction, it can generate what?

A

Lactate

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5
Q

What reaction does pyruvate dehydrogenase catalyze?

A

Pyruvate + NAD+ + CoA-SH –> Acetyl-CoA + NADH + CO2

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6
Q

Pyruvate diffuses through the pores in the outer mitochondrial membrane and is transported across the inner mitochondrial membrane into the (blank), where it is oxidatively decarboxylated to (blank).

A

mitochondrial matrix; acetyl-CoA

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7
Q

Pyruvate dehydrogenase catalyzes an irreversible reaction. What kind of reaction is this considered?

A

an oxidative decarboxylation

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8
Q

What kind of dehydrogenase is pyruvate DH?

A

an alpha-ketoacid dehdrogenase

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9
Q

3 catalytic enzymes of the PDH complex

A 
E1 = pyruvate dehydrogenase
E2 = DLTA
E3 = DLDH
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10
Q

5 coenzymes of the PDH complex

A 
TPP
CoA
NAD+
FAD+
Lipoamide
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11
Q 
What vitamins do these coenzymes require?
TPP
CoA
NAD
FAD
Lipoamide
A 
TPP --> thiamine (B1)
CoA --> Panthothenic acid (B5)
NAD --> Niacin (B3)
FAD --> Riboflavin (B2)
Lipoamide --> none
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12
Q

TPP is the coenzyme form of what?

A

Vitamin B1

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13
Q

Lipoamide is required for which catalytic enzyme? It is a carrier of what?

A

E2; an acetyl group

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14
Q

Which catalytic enzyme requires CoA?

A

DLTA

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15
Q

NAD and FAD are required for what catalytic enzyme?

A

DLDH

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16
Q

NAD+ functions in (blank) transfers, while FAD functions in (blank) transfers.

A

hydride; electron

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17
Q

How is the pyruvate dehydrogenase complex regulated? When is it active vs. inactive?

A

Regulated by phoshorylation; INACTIVE when phosphorylated

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18
Q

Beriberi is caused by a deficiency in this amino acid.

A

A deficiency in thiamine

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19
Q

Complete glucose oxidation begins where and ends where?

A

Begins in cytoplasm and ends in mitochondria

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20
Q

What molecule is the GATEWAY to oxidative metabolism of the food we eat?

A

Acetyl-CoA

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21
Q

How many NADH and FADH2 are generated for each turn of the TCA cycle?

A

3; 1

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22
Q

What is the limiting substrate of the TCA cycle?

A

OAA

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23
Q

3 blood glucose sources

A

Food
Glycogen degradation
Gluconeogenesis

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24
Q

What three things can gluconeogenesis produce glucose from?

A

amino acids, lactic acid, and glycerol

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25
Q

Discuss the Cori cycle.

A

Lactate enters the liver and is converted to glucose, which can then be transported to RBCs and back to lactate.

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26
Q

Both of these cycles rely on gluconeogenesis in liver followed by delivery of glucose and its use in a peripheral tissue.

A

Cori cycle

Alanine cycle

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27
Q

What are the 3 irreversible steps of glycolysis?

A

Glucokinase
PFK1
Pyruvate Kinase

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28
Q

2 enzymatic steps that take pyruvate back to PEP

A
  1. pyruvate carboxylase

2. PEP carboxykinase

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29
Q

What is the enzyme that takes F1,6BP back to F6P?

A

Fructose 1,6 Bisphosphatase (F1,6BPase)

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30
Q

What is the enzyme that takes G6P back to glucose?

A

Glucose 6 phosphatase

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31
Q

Where does the rxn catalyzed by pyruvate carboxylase occur?

A

In the mito

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32
Q

Where does the rxn catalyzed by PEP carboxykinase occur?

A

In the cytosol or in the mito

33
Q

Where does the rxn catalyzed by Fructose 1,6 BPase occur?

A

In the cytosol

34
Q

Where does the rxn catalyzed by Glucose 6 phosphatase occur?

A

In the ER

35
Q

Pyruvate carboxylase take pyruvate to what intermediate? What cofactor is it dependent on? What does this reaction require?

A

OAA; Biotin; ATP

36
Q

The second reaction in converting OAA back to PEP involves what enzyme? What does this reaction require?

A

PEP carboxykinase; GTP

37
Q

What is the first bypass in gluconeogenesis?

A

Taking pyruvate back to PEP through a two step reaction

38
Q

What is the second bypass in gluconeogenesis? What enzyme is required?

A

Taking F-1,6,BP to F6P; F-1,6BPase

39
Q

What is the third bypass in gluconeogenesis? What enzyme is required?

A

Taking G6P to to glucose; G6Pase

40
Q

Lactate generates (blank) when it is converted to Pyruvate, therefore there is no net loss of (blank) in gluconeogenesis from Lactate

A

NADH

41
Q

Is it “cheaper” to make glucose from lactate or pyruvate?

A

From lactate, because you generate 2 NADH to cancel out the 2 NADH lost

42
Q

How does ATP affect pyruvate kinase?

A

inhibits it

43
Q

How does acetyl-CoA affect pyruvate carboxylase?

A

activates it

44
Q

How do citrate and ATP affect F1,6BPase?

A

activate it

45
Q

How do citrate and ATP affect PFK1?

A

inhibit it

46
Q

Does F-2,6-BP inhibit or activate glycolysis? Does it inhibit or activate gluconeogenesis?

A

activates glycolysis, by stimulating PFK1

inhibits gluconeogenesis by blocking F-1,6-BPase

47
Q

What activates pyruvate kinase? What inhibits it?

A

F-1,6-BP; ATP, alanine, phosphorylation

48
Q

What activates pyruvate carboxylase? What inhibits it?

A

Acetyl-CoA; ADP

49
Q

What activates PFK1? What inhibits it?

A

F2,6BP; ATP, citrate

50
Q

What activates F-1,6-BPase? What inhibits it?

A

ATP and citrate; F-2,6-BP

51
Q

What does glucagon/epinephrine do to blood glucose levels?

A

Increases them

52
Q

What does insulin do to blood glucose levels

A

Decreases

53
Q

Describe the G-protein coupled receptor signaling that occurs with glucagon/epinephrine

A 
Hormone binds receptor.
GDP is released → GTP binds. 
Gα translocates to adenylate cyclase.
cAMP is generated.
Protein kinase A is ACTIVATED.
Regulated proteins get phosphorylated.
54
Q

What does glucagon do to pyruvate kinase? What effect does this have? What affect does this have on glycolysis?

A

phosphorylates it; inactivates it; turns glycolysis off

55
Q

In the presence of insulin, which way does the following reaction go?

F6P F-2,6-BP

A

To the right; insulin means there is plenty of blood glucose

56
Q

In the presence of glucagon, which way does the following reaction go?

F6P F-2,6-BP

A

To the left; glucagon signals fasting, so it will not want to produce F-2,6-BP because that activates further glycolysis. Need to store glucose!

57
Q

In the presence of glucagon, what enzyme is phosphorylated so that it stops producing F-2,6-BP?

A

PFK2-F2,6BPase

58
Q

A bifunctional enzyme with both kinase and phosphatase activity

A

PFK2-F2,6BPase

59
Q

Stimulate gluconeogenesis by inducing the synthesis of gluconeogenic enzymes.

A

glucocorticoids

60
Q

Besides carbohydrates, what else can be used to make glucose?

A 
Lactate
Alanine and some other AAs (not leucine or lysine)
OAA
Glycerol
Odd chain fatty acids
61
Q

Describe the steps in ethanol degradation

A

Ethanol –> Acetaldehyde –> Acetate –> Acetyl-CoA

62
Q

What enzyme takes ethanol to acetaldehyde? Where does this reaction occur?

A

Alcohol dehydrogenase; in the cytoplasm

63
Q

What enzyme takes acetaldehyde to acetate? Where does this step occur?

A

Aldehyde dehydrogenase; in the mito

64
Q

What enzyme takes acetate to acetyl-CoA? Where does this step occur?

A

Acetyl-CoA synthase; mito or cytoplasm

65
Q

What is the rate limiting step of alcohol metabolism?

A

Alcohol dehydrogenase

66
Q

What step in the pathway of alcohol metabolism does antabuse block?

A

acetaldehyde –> acetate

67
Q

Alcohol can be converted into one of two things

A
  1. ketones

2. fatty acids

68
Q

In the liver, acetate is converted to Acetyl-CoA and ketones are made. What is an example of a ketones that can be generated?

A

alpha-3-hydroxybutyrate

69
Q

Ketones cannot be metabolized by the liver and do what to the plasma pH?

A

decrease it leading to acidosis

70
Q

Ethanol disrupts the metabolism of which two vitamins?

A

Vitamin A

Thiamine (Vit B1)

71
Q

3 stages of liver damage

A
  1. Fatty liver from increased TAG synthesis
  2. Alcohol hepatitis
  3. Cirrhosis
72
Q

What is the major gluconeogenic organ?

A

Liver

73
Q

The cori cycle and the alanine cycle both depend on gluconeogenesis in the (blank) followed by delivery of glucose and its use in a peripheral tissue

A

liver

74
Q

A defect in glucose 6 phosphatase can cause this disease

A

von Gierke’s disease

75
Q

What converts alanine to pyruvate?

A

a transaminase

76
Q

What converts lactate to pyruvate?

A

lactate dehydrogenase

77
Q

Competitive inhibitor of F-1,6-BPase

A

F-2,6-BP

78
Q

This enzyme of glycolysis is less activate when phosphorylated.

A

pyruvate kinase

Block 3 Week 1 Meg (17 decks)

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