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Metabolic Pathways Flashcards

1
Q

Site of citric acid cycle

A

Mitochondrial matrix

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2
Q

Major roles of CAC

A
  1. Generate ATP by generating reduced carriers for oxidative phosphorylation (NADH and FADH2) and a GTP
  2. Generate metabolic precursors
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3
Q

Substrate of CAC

A

Acetyl-CoA

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4
Q

Where can substrate for CAC come from?

A

From pyruvate (glycolysis), B-oxidation of fatty acids, or ketogenic amino acids

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5
Q

Metabolic product of CAC

A

Oxaloacetate

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6
Q

Key/entry enzyme of CAC

A

Citrate synthase (acetyl-CoA + OAA –> citrate)

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7
Q

What are the other important products of the CAC?

A

3 NADH (formation of α-ketoglutarate, succinyl CoA, and OAA), 1 FADH2 (formation of fumarate), 1 GTP (formation of succinate), 2 CO2 (α-KG and succinyl CoA)

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8
Q

Site of PDH complex

A

Mitochondrial matrix

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9
Q

Major role of PDH complex

A

Links glycolysis to CAC

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10
Q

Substrate for PDH complex

A

Pyruvate

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11
Q

Where does the substrate for PDH complex come from?

A

Mainly glycolysis, also alanine and lactate

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12
Q

Metabolic product of PDH complex

A

Acetyl-CoA

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13
Q

Key/entry enzyme for PDH complex

A

Pyruvate dehydrogenase (PDH) complex

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14
Q

What are the other important products of PDH complex?

A

1 NADH, 1 CO2 (by decarboxylation)

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15
Q

4 B-vitamins involved in PDH complex reaction

A
  1. Riboflavin (B2, FAD)
  2. Niacin (B3, NAD)
  3. Thiamin (B1, TPP)
  4. Pantothenic acid (B5, CoA)
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16
Q

What does deficiency of niacin lead to?

A

Pellagra (4 D’s)

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17
Q

What does deficiency of thiamin lead to?

A

Beri-beri (alcoholics, elderly, and low-income)

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18
Q

Lactic acidosis and PDH complex

A

Decreased complex activity leads to lactate generation

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19
Q

Site of glycolysis

A

Cytosol

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20
Q

Major role of glycolysis

A

Generate ATP (and pyruvate)

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21
Q

Substrate of glycolysis

A

Glucose (and other hexoses)

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22
Q

Metabolic product of glycolysis

A

Pyruvate (–> lactate in anaerobic conditions or RBCs)

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23
Q

Key/entry enzymes of glycolysis

A
  1. Hexokinase (entry)
  2. Phosphofructokinase (key regulator)
  3. Pyruvate kinase (forms ATP)
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24
Q

What does deficiency of pyruvate kinase in glycolysis lead to?

A

Hereditary nonspherocytic hemolytic anemia

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25
Q

What are the other important products of glycolysis?

A

2 NADH per glucose, 2 net ATP per glucose

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26
Q

What happens after glycolysis in aerobic conditions?

A

Pyruvate –> acetyl-CoA –> CAC

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27
Q

What happens after glycolysis in anaerobic conditions?

A

Pyruvate –> lactate to regenerate NAD+

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28
Q

Site of gluconeogenesis

A

Cytosol (mainly – also mitochondria)

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29
Q

Major role of gluconeogenesis

A

Generation of blood glucose

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30
Q

Substrates of gluconeogenesis

A
  1. Lactate (via pyruvate)
  2. Glycerol (from TAG breakdown)
  3. Gluconeogenic amino acids, especially glutamine and alanine
    - -Also ODD chain-length fatty acids (NOT acetyl-CoA)
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31
Q

Metabolic product of gluconeogenesis

A

Glucose

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32
Q

Key/entry enzymes in gluconeogenesis

A
  1. Pyruvate carboxylase (pyruvate –> oxaloacetate)
  2. PEP carboxykinase (OAA –> phosphoenolpyruvate)
    - –F1,6-bisphosphatase (F1,6BP –> F6P)***
  3. G-6-phosphatase (G6P –> glucose)
33
Q

Which organ does gluconeogenesis mainly occur in?

A

Liver (kidney in starvation)

34
Q

Site of glycogenesis

35
Q

Major role of glycogenesis

A

Storage of glucose or G6P as glycogen

36
Q

Substrate of glycogenesis

A

G6P (from glycolysis)

37
Q

Metabolic product of glycogenesis

38
Q

Key/entry enzyme of glycogenesis

A

Glycogen synthase

39
Q

How can glycogenesis be inhibited?

A

By phosphorylation of enzymes in response to hormones

40
Q

Site of glycogenolysis

41
Q

Major roles of glycogenolysis

A
  1. Supply glucose for ATP generation for contraction (muscle)
  2. Maintain blood glucose (liver)
42
Q

Substrate for glycogenolysis

43
Q

Metabolic product of glycogenolysis

A

G6P or glucose in liver

44
Q

Key/entry enzyme of glycogenolysis

A

Glycogen phosphorylase (forms G1P with Pi)

45
Q

Site of pentose phosphate pathway

46
Q

Major roles of PPP

A
  1. Form NADPH for biosynthesis

2. Form ribose-5-P for nucleotide synthesis

47
Q

Substrate of PPP

A

G6P (from glycolysis)

48
Q

Metabolic products of PPP

A

Ribose-5-P, fructose-6-P and glyceraldehyde-3-P (glycolysis), 2 NADPH per glucose

49
Q

What are the other important products of PPP?

A

1 CO2 per glucose

50
Q

Key/entry enzyme of PPP

A

G6PD (forms NADPH)

51
Q

What dose deficiency of G6PD lead to?

A

Hemolytic anemia and Heinz bodies in RBCs

52
Q

Site of fatty acid B-oxidation

A

Mitochondrial matrix

53
Q

Major roles of fatty acid B-oxidation

A
  1. Generate acetyl-CoA for ATP production via CAC and oxidative phosphorylation
  2. Generate FADH2 and NADH for ATP generation via oxidative phosphorylation
54
Q

Substrate for fatty acid B-oxidation

A

Fatty acyl-CoA

55
Q

Metabolic product of fatty acid B-oxidation

A

Acetyl-CoA

56
Q

What are the other important products of fatty acid B-oxidation?

A

FADH2 (2 ATP via ox-phos), NADH (3 ATP)

57
Q

How does uptake of long chain fatty acids occur in mitochondria?

A

Facilitation by carnitine

58
Q

How are fatty acids carried from adipocytes?

A

By albumin in serum

59
Q

What types of tissues/organs prefer fatty acids?

A

Red muscle tissue; anything with abundant mitochondria

60
Q

Where does B-oxidation of very long chain fatty acids occur initially?

A

Peroxisomes

61
Q

What states promote a higher rate of fatty acid B-oxidation?

A

Fasting/starvation, uncontrolled diabetes, and low carbohydrate diets

62
Q

Site of fatty acid biosynthesis

63
Q

Major role of fatty acid biosynthesis

A

Make fatty acids, mainly for storage

64
Q

Substrate for fatty acid biosynthesis

A

Acetyl-CoA (carboxylated to malonyl-CoA)

65
Q

Metabolic product of fatty acid biosynthesis

A

Saturated fatty acids, mainly C16 palmitate

66
Q

What are other important products of fatty acid biosynthesis?

A

NADP+ from NADPH (2 NADPH required for every 2C) and CO2 from malonyl-CoA

67
Q

Key/entry enzyme of fatty acid biosynthesis

A
  1. Acetyl-CoA carboxylase (acetyl-CoA + CO2 –> malonyl-CoA) – REQUIRES ATP
  2. Fatty acid synthase complex
68
Q

What needs to occur with the substrate before fatty acid biosynthesis can occur?

A

Acetyl-CoA groups are formed in mitochondria – need to be transported to cytosol as citrate and cleaved to acetyl-CoA and OAA

69
Q

What provides the attachment site in synthase complex of fatty acid biosynthesis?

A

Phosphopantotheine with -SH group, a derivative of pantothenic acid (vitamin B5)

70
Q

Site of ketogenesis

A

Mitochondria

71
Q

Major role of ketogenesis

A

Form water-soluble derivatives of fatty acids (ketone bodies) which can serve as important metabolic fuels for many tissues, especially the brain

72
Q

Substrate for ketogenesis

A

Acetyl-CoA

73
Q

Metabolic products of ketogenesis

A

3 ketone bodies:

  1. Acetoacetate
  2. B-hydroxybutyrate
  3. Acetone
74
Q

Why would ketogenesis occur?

A

Spares utilization of glucose and endogenous protein

75
Q

What states promote higher rate of ketogenesis?

A

Starvation, poorly controlled diabetes (especially type I), and low carbohydrate diets

76
Q

What is the reaction catalyzed by pyruvate carboxylase?

A

Pyruvate –> OAA

77
Q

What enzymes use biotin?

A
  • -Pyruvate carboxylase

- -Acetyl-CoA carboxylase

78
Q

What processes occur in the well-fed state?

A

CAC, glycolysis, PDH complex, glycogenenesis, fatty acid biosynthesis

79
Q

What processes occur in fasting state?

A

Gluconeogenesis, glycogenolysis, fatty acid B-oxidation, ketogenesis

Biochemistry (14 decks)

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