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BIOC 3300 > Week 2 => Glycogen and PPP, TCA cycle, and AA Degradation (Urea Cycle) > Flashcards

Week 2 => Glycogen and PPP, TCA cycle, and AA Degradation (Urea Cycle) Flashcards

1
Q

Glycogen linear chain

A

alpha 1,4-glycosidic bonds

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2
Q

Glycogen branch points

A

alpha 1,6-glycosidic bonds

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3
Q

Reducing end

A

Anomeric carbon (C1 of glucose)

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4
Q

Purpose of glycogen degradation in liver?

A

Maintaining blood glucose

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5
Q

Major energy storage molecule in the body?

A

Glycogen

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6
Q

Why do glycogenin-glucose chains serve as “primers” for glycogen synthase?

A

To extend with additional UDP-glucose units (alpha 1,4-linkages)

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7
Q

Precursor for glucose addition to glycogen chains?

A

UDP-glucose

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8
Q

Function of UDP-Glucose Pyrophosphorylase

A

Formation of glucose-glucose linkage in glycogen costs energy

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9
Q

What are branches important?

A
  • To increase the solubility of polymeric glucose
  • To allow multiple sites for glucose release (faster degradation)
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10
Q

Andersen disease

A

Mutation in liver branching enzyme. Abnormal glycogen structure. Failure to thrive, cirrhosis

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11
Q

Glycogen Degradation Enzymes

A
  • Phophorolysis
  • Glycogen phosphorylase (regulated step)
  • Debranching enzyme
  • Phosphoglucomutase
  • Glucose-6-phosphatase
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12
Q

Cofactor for glycogen phosphorylase

A

Pyridoxal phosphate

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13
Q

Muscle enzyme used in glycolysis

A

Phosphoglucomutase

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14
Q

Liver enzyme used in glycolysis

A

Glucose-6-phophatase

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15
Q

McArdle Disease

A

Mutations in muscle glycogen phosphorylase. Impaired muscle glycogen degradation leads to muscle weakness and fatigue

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16
Q

2 activates of debranching enzymes

A

alpha 1,4-alpha1,4-glucantrasnferase and alpha 1,6-glucosidase

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17
Q

alpha 1,4-alpha1,4-glucantrasnferase

A

activity transfers triglucose from the branchpoint chain to another outer branch

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18
Q

alpha 1,6-glucosidase

A

activity releases the last glucose from the branchpoint

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19
Q

Forbes/Cori Disease

A

Mutations in liver and muscle debranching enzyme. Hypoglycemia during fasting, muscle weakness

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20
Q

Glycogen phosphorylase (GP) (form, activation)

A
  • Homodimer
  • activated by phosphorylation
  • Even when not phosphorylated, high levels of AMP can activate the enzyme allosterically
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21
Q

Glycogen Phosphorylase (GP) two levels of regulation

A

a) Local (cellular) energy status: AMP allosteric activator, glucose-6P and ATP overcome the activation
b) Tissue/organism level: Need for glucose during fasting (liver), need for glycolysis (muscle). Hormonal regulation of phosphorylation

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22
Q

Phosphorylase kinase reaction

A

phosphorylates glycogen phosphorylase –> more active form

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23
Q

Phosphoprotein phosphatase reaction

A

dephosphorylates glycogen phosphorylates –> less active form, but can still be allosterically activated by high ATP and/or G6P

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24
Q

Phosphorylase kinase is activated when ___

A

cAMP increases and protein kinase A is activated

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25
Q

Phosphoprotein phosphatase is activated ___

A

In response to insulin

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26
Q

Pentose phosphate pathway substrates

A

Glucose-6-phosphate, NADP+

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27
Q

Pentose phosphate pathway products

A

NADPH, Co2, Pentose (Ribulose-5-phosphate)

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28
Q

Pentose phosphate pathway oxidative stage:

A

Synthesis of NADPH and pentose sugar

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29
Q

What happens to pentose that are not used for nucleotides?

A

They are metabolized in glycolysis

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30
Q

Glucose-6-phosphate dehydorgenase

A

Catalyzes first step of the PP, inhibited by NADPH

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31
Q

NADPH

A
  • Required for cholesterol and fatty acid synthesis
  • Required for regeneration of glutathione (antioxidant)
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32
Q

Pyruvate dehydrogenase complex

A

Oxidation of pyruvate to acetyl-CoA

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33
Q

What is “Coenzyme A” a derivative of ?

A

ADP and pantothenic acid (from vitamin B5)

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34
Q

What functional group is on Free coenzyme A

A

a thiol group (can form thioester bonds)

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35
Q

CoASH

A

Coenzyme A with SH-group

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36
Q

CoA

A

Coenzyme A esterified to an acyl group

37
Q

Pathways Acetyl-CoA can enter?

A
  • Oxidation in TCA cycle (in mitochondria)
  • Precursor for many larger metabolites (in cytosol)
38
Q

Thiamine pyrophosphate (TPP)

A

Cofactor for decarboxylations of ketoacids

39
Q

Lipoamide

A

Derived form lipoic acid, acyl group and electron carrier

40
Q

Flavin coenzymes FAD & FMN

A

Derived form riboflavin (vitamin B2), electron transfer reactions via reduction of ring system

41
Q

Coenzymes in PDH and other dehydrogenases

A

1) Thiamine pyrophosphate (TPP)
2) Lipoamide
3)Flavin coenzymes FAD & FMN

42
Q

Pyruvate Dehydrogenase (PDH) Complex

A
  • Complex of 3 enzymes and 5 coenzymes
  • Contains up to 60 subunits (depending on species) that convert pyruvate to acetyl-CoA
43
Q

3 enzymes in PDH

A

1) Pyruvate dehydrogenase/decarboxylase
2) Dihydrolipoamide transacetylase
3) Dihydrolipoamide dehydrogenase

44
Q

5 cofactors of PDH

A

1) TPP
2) Lipoic acid
3) Coenzyme A (CoA)
4) Flavin adenine dinucleotide (FAD)
5) nicotinamide adenine dinucleotide (NAD+)

45
Q

PDH allosteric regualtion

A

PDH is allosterically inhibited by Acetyl-CoA and NADH (product inhibition)

46
Q

Regulation of PDH activity by phosphorylation

A

PDH kinase phosphorylates PDH and inactivates PDH.
PDH phosphatase dephosphorylates PDH and activates PDH

47
Q

Reaction 1 of Citric Acid Cycle

A

Citrate synthase adds the acetyl group from acetyl-CoA to oxaloacetate (irreversible)

48
Q

Reaction 2 of Citric Acid Cycle

A

Isomerization to isocitrate (reversible)

49
Q

First decarboxylation (citric acid cycle)

A

Isocitrate dehydrogenase

50
Q

Second decarboxylation (citric acid cycle)

A

alpha-ketoglutarate dehydrogenase

51
Q

Succinyl Synthetase

A

Formation of 1 GTP

52
Q

Succinate dehydrogenase

A

Oxidation of succinate to fumarate coupled to reduction of ubiquinone Q to ubiquinol QH2.

53
Q

Fumerase

A

Hydration of fumarate to malate

54
Q

Malate dehydrogenase

A

Oxidations of malate to oxaloacetate coupled to reduction to NAD+ to NADH

55
Q

What does TCA serve as a source for?

A

both energy and of metabolic intermediates

56
Q

Anaplerotic reactions

A

Replenishment of TCA cycle intermediates

57
Q

Processes that replenish intermediates in the cycle:

A

a) Oxaloacetate
b) Malice enzyme
c) Transamination reactions

58
Q

Cataplerotic reactions

A

TCA cycle intermediates are precursors of other molecules

59
Q

Glucogenic

A

can be converted to glucose

60
Q

Metabolites that can be converted to glucose through gluconeogenesis

A

Glucogenic

61
Q

Metabolites that cannot be converted to glucose through gluconeogenesis

A

Ketogenic

62
Q

Nonessential amino acids

A

alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine

63
Q

Essential amino acids

A

Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine

64
Q

Transamination Reactions

A

Amino groups can be transferred from molecule to molecule. Involve enzymes called transaminases or aminotransferases (same enzyme)

65
Q

Transamination examples

A

Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST)

66
Q

Prosthetic group of all transaminases?

A

Pyridoxal phosphate PLP

67
Q

Reductive Amination

A

Synthesis of amino acid

68
Q

Oxidative Deamination

A

Degradation of amino acid

69
Q

Glutamate dehydrogenase

A

Catalyze glutamate and alpha-ketoglutarate interconversion by reductive amination/oxidative deamination

70
Q

What reaction uses free ammonium?

A

Glutamine synthetase reaction

71
Q

What reaction releases ammonium?

A

Deamidation of glutamine to glutamate

72
Q

Glutaminase

A

converts glutamine to glutamate (deamidation)

73
Q

Where are most amino acids degraded?

A

The liver

74
Q

Amino acid oxidation in humans occurs mainly in three metabolic states

A

1) Basal
2) High protein diet
3) starvation or diabetes mellitus
4) Lack of essential amino acids

75
Q

Basal metabolic state

A

Amino acids generated by continual biosynthesis and degradation of cell proteins

76
Q

High protein diet metabolic state

A

In take exceeds requirement for protein synthesis

77
Q

Starvation or diabetes mellitus

A

Carbohydrate is not available or is improperly utilized

78
Q

Lack of essential amino acids metabolic state

A

Protein synthesis is impaired, other amino acids are degraded

79
Q

Negative N(nitrogen) balance: N (in) < N (out)

A
  • starvation
  • serious illness
  • insufficient essential aa
80
Q

Positive N(nitrogen) balance: N (in) > N (out)

A
  • Growth
  • Pregnancy
  • Recovery illness or starvation
81
Q

Forms of excreted excess nitrogen

A
  • Ammonia
  • Urea
  • Uric acid
82
Q

Urea cycle direct substrates

A

Aspartate and carbamoyl phosphate (from ammonia and bicarbonate)

83
Q

Urea cycle products

A

Urea and fumerate

84
Q

Carbamoyl phosphate synthetase

A

controls urea production (investment of energy to generate a transferable amino group)

85
Q

Mitochondrial carbamoyl phosphate synthetase CPS1 enzyme tunnel shielding and channeling

A

Shielding: protect reactive intermediate
Channeling: prevent loss of intermediates concentrate them locally

86
Q

Urea cycle 5 enzymes

A

1) Carbamoyl phosphate synthase 1
2) Ornithine transcarbamoylase (OTC)
3) Arginosuccinate synthetase (ASS)
4) Arginosuccinate lyase
5) Arginase

87
Q

What activates CSP1?

A

N-acetylglutamate (NAG) => increases CSP1 affinity for ATP

88
Q

Processes for detoxification for NH4+

A

through glutamine synthetase or glutamate dehydrogenase

89
Q

Aspartate-arginosuccinate shunt

A

Pathway linking TCA cycle and urea cycle

BIOC 3300 (3 decks)

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