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Biochemistry > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Compounds that have the same chemical formula but different structures

A

Isomers

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2
Q

Compounds that differ in configuration around only one specific carbon atom with the exception of the carbonyl carbon

A

Epimers

Alpha-D-galactose, Alpha-D-glucose, Alpha-D-mannose

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3
Q

Pairs of structures that are mirror images of each other

A

Enantiomers

D-glucose and L-glucose

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4
Q

Sugars that are convertible between a linear form and a ring form

A

Anomers

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5
Q

Fischer projection

A

Linear form

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6
Q

Haworth projection

A

Ring form

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7
Q

Alpha and beta configurations of the ring forms of sugar can spontaneously interconvert through a process called

A

Mutarotation

No need for enzyme

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8
Q

Amylase digests what bonds

A

Alpha (1–>4)

Cellulose has beta (1->4)

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9
Q

Glucose transporter in the basolateral membrane of intestinal cells

A

Glut-2

All sugars
Facilitated diffusion

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10
Q

Glut 5 is found in the lumen or basolateral membrane?

A

Luminal membrane

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11
Q

Test that tells how fast a carbohydrate is absorbed

A

Glycemic index

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12
Q

Reference in glycemic index

A

Glucose and galactose

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13
Q

If glycemic index is >1, what does this mean?

A

Fast absorption

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14
Q

Anabolic vs catabolic: Endergonic and divergent procss

A

Anabolic

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15
Q

Anabolic vs catabolic: exergonic and convergent process

A

Catabolic

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16
Q

Crossroads of metabolism or the link between anabolic and catabolic pathways

A

Amphibolic

Kreb’s cycle

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17
Q

Glucose transporter in the erythrocyte

A

Glut 1

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18
Q

2 Glucose transporters in the brain

A

Glute 1 and 3

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19
Q

3 glucose transporters in the kidney

A

Glut 1,2,3

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20
Q

Glut transported in the liver and pancreatic B cell

A

Glut 2

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21
Q

Glucose transporter in the placenta

A

Glut 3

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22
Q

Glucose transporter in the heart, skeletal muscle and adipose tissues

A

Glut 4

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23
Q

Insulin stimulated glucose transporter

A

Glut 4

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24
Q

Glycolysis is also known as

A

Embden meyerhoff pathway

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25
Q

Major pathway for glucose metabolism that converts glucose into 3 carbon compounds to povide energy

A

Glycolysis

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26
Q

End product of glycolysis

A

Pyruvate or lactate

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27
Q

Rate limiting step for glycolysis

A

Phosphofructokinase 1

F-6-PO4 -> F-1,6-biPO4

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28
Q

Catalyzes glucose to glucose-6-PO4

A

Hexokinase or glucokinase

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29
Q

3 irreversible and regulated steps in glycolysis

A

Hexokinase or glucokinase
PFK-1
Pyruvate kinase

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30
Q

Hexokinase vs glucokinase: present only in liver and pancreas

A

Glucokinase

Hexokinase - in most tissues

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31
Q

Hexokinase vs glucokinase: inhibuted by glucose-6-P

A

Hexokinase

Glucokinase by Fructose-6-P

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32
Q

Hexokinase vs glucokinase: low Km

A

Hexokinase

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33
Q

Hexokinase vs glucokinase: high Vmax

A

Glucokinase

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34
Q

Activator of PFK-1

A

Fructose-2,6-BP and AMP

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35
Q

Converts Fru-6-P to Fru-2,6-BP

A

PFK-2

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36
Q

Inhibitor of PFK-1

A

ATP and Citrate

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37
Q

2 steps in glycolysis that produce ATP via substrate level phosphorylation

A

1,3-biphosphoglycerate –> 3-phosphoglycerate (phosphoglycerate kinase)

PEP –> pyruvate (pyruvate kinase)

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38
Q

Activator of pyruvate kinase

A

Fructose-1,6-BP

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39
Q

1 step in glycolysis that produces NADH

A

Glyceraldehyde-3-PO4 –> 1,3-bisphosphoglycerate (glyceraldehyde-3-PO4 dehydrogenase)

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40
Q

Shuttle of NADH to inner mitochondrial membrane in the liver, kidney and heart

A

Malate-Aspartate Shuttle

NADH - 3 ATP

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41
Q

Shuttle of NADH to inner mitochondrial membrane in the skeletal muscle and brain

A

Glycerol PO4 shuttle

NADH - 2 ATP

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42
Q

Used to reduce pyruvate to lactate

A

NADH

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43
Q

5 Strictly glycolytic organs/cells

A

RBCs, lens and cornea, kidney medulla, testes and WBCs

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44
Q

Total ATP yield in aerobic glycolysis

A

6 or 8 (including the 2 NADH)

Anaerobic - 2

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45
Q

Inhibits pyruvate dehydrogenase by binding to lipoic acid

A

Arsenic

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46
Q

Competes with inorganic PO4 as a substrate for glyceraldehyde-3-P-dehydrogenase

A

Arsenic

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47
Q

Most common enzyme defect in glycolysis

A

Pyruvate kinase

Chronic hemolytic anemia

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48
Q

Fate of pyruvate in fasting or starvation

A

Oxaloacetate by pyruvaye carboxylase (gluconeogenesis)

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49
Q

Pyruvate may be fermented by pyruvate decarboxylase to

A

Ethanol

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50
Q

5 conenzymes in pyruvate dehydrogenase complex

A

Thiamine PP, FAD, NAD, Coenzyme A (pantothenic acid), lipoic acid

Pyruvate to Acetyl CoA

Love Never Fails To Conquer

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51
Q

Products of pyruvate dehydrogenase complex

A

Acetyl CoA, NADH, CO2

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52
Q

Most common biochemical cause of congenital lactic acidosis

A

Pyruvate dehydrogenase deficiency

X-linked dominant

Tx: ketogenic diet

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53
Q

Final common pathway for the aerobic oxidation of all nutrients

A

Krebs or TCA

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54
Q

All enzymes in the Krebs cycle are in the mitochondrial matrix exceot

A

Succinate dehydrogenase (inner mitochondrial membrane)

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55
Q

Provides majority of ATP for energy

A

Krebs

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56
Q

4 products of Krebs cycle

A

CO2, GTP, NADH, FADH2

57
Q

3 steps in TCA that produce NADH

A

Isocitrate –> alpha-ketoglutarate
Alpha-ketoglutarate –> succinyl CoA
Malate –> oxaloacetate

58
Q

A step in TCA that produces FADH2

A

Succinate –> fumarate

59
Q

Step in TCA that produces GTP

A

Succinyl CoA –> succinate (substrate level phosphorylation)

Succinate thiokinase

60
Q

Rate limiting step and enzyme in TCA

A

Isocitrate –> alpha ketoglutarate (isocitrate dehydrogenase)

61
Q

8 intermediates in TCA

A

Officer, Can I Keep Selling Sex For Money?

Oxaloacetate
Citrate
Isocitrate
alpha-Ketoglutarate
Succinyl CoA
Succinate
Fumarate
Malate
62
Q

Converts citrate to isocitrate

A

Aconitase

63
Q

Rat poison or fluoroacetate inhibits what enzyme in TCA?

A

Aconitase (citrate to isocitrate)

64
Q

Intermediate of TCA that delivers acetyl CoA to the cytoplasm for FA synthesis

A

Citrate

65
Q

Intermediate of TCA that is used ti activate ketone bodies in extrahepatic tissues

A

Succinyl CoA

66
Q

TCA intermediate that may be used for gluconeogenesis

A

Malate

67
Q

Organs where gluconeogenesis occurs

A

Liver(90%) and kidney (10%)

During prolonges fasting, kidney contributes 40%

68
Q

Substrate for gluconeogenesis

A

Pyruvate

69
Q

Rate limiting step and enzyme in gluconeogenesis

A

Fructose-1,6-bisphosphate –> fru-6-P
(Fru-6-bisphosphatase)

Activator: ATP
Inhibitor: fru-2,6-BP and AMP

70
Q

Number of ATPs used in Cori cycle

A

4

71
Q

Reverses glucokinase

A

Glucose-6-phosphatase

Only in the liver and kidneys

72
Q

Reverses PFK-1

A

Fru-1,6-bisphosphatase (fru-1,6-BP to Fru-6-P)

73
Q

Reverses pyruvate kinase

A

PEP carboxylase

74
Q

Disulfiram drugs inhibit

A

Acetaldehyde dehydrogenase

75
Q

Glycogen is a branched polymer of

A

Alpha-D-glucose

76
Q

4 Substrates for glycogenesis

A

UDP-glucose, ATP, UTP, glycogenin

77
Q

Rate limiting enzyme for glycogenesis

A

Glycogen synthase

78
Q

Enzyme converting glu-6-P to glu-1-P

A

Phosphoglucomutase

79
Q

Activated form of glucose

A

UDP-glucose

From glucose-1-P and UTP by UDP glucose phosphorylase

80
Q

In glycogenolysis, how many glucose residues are left before a branch point?

A

4

Limit dextrin

81
Q

Products of glycogenolysis

A

Glu-1-P and free glucose (produced during debranching)

82
Q

Rate limiting enzyme for glycogenolysis

A

Glycogen phosphorylase

83
Q

What is the active form of glycogen synthase?

A

Dephosphorylated

84
Q

What is the active form of glycogen phosphorylase?

A

Phosphorylated

85
Q

Type 1 glycogen storage disease

A

Von Gierke’s

86
Q

Type II glycogen storage disease

A

Pompe’s

87
Q

Type III glycogen storage disease

A

Cori’s

88
Q

Type IV glycogen storage disease

A

Andersen’s

89
Q

Type V glycogen storage disease

A

McArdle’s

90
Q

Type VI glycogen storage disease

A

Her’s

91
Q

Type VII glycogen storage disease

A

Tarui’s

92
Q

Deficiency of Glu-6-phosphatase

A

Type I or Von Gierke’s

In liver and renal
Hepatomegaly, hypoglycemia + lactic acidosis

93
Q

Deficiency of acid maltase

A

Type II or Pompe’s

Glycogen in lysosomes
Cardiomegaly and HF

94
Q

Defeciency in debranching enzyme of glycogen

A

Type III or Cori’s

Mild

95
Q

Deficiency in branching enzyme of glycogen

A

Type IV or Andersen’s

Severe form

96
Q

Defeciency in skeletal muscle glycogen phosphorylase

A

Type V or McArdles

Glycogen in muscle
Muscle cramps + myoglobinuria but no lactic acidosis; no hypoglycemia

97
Q

Deficiency in hepatic glycogen phosphorylase

A

Hers or Type VI

Glycogen in liver cells; hypoglycemia

98
Q

Deficiency in PFK

A

Type VII or Tarui’s

99
Q

Deficiency in hepatic phosphorylase kinase

A

Type VIII

100
Q

Absence of galactose 1-P uridyltransferase

A

Classic galactosemia

Accumulation of galactitol –> cataracts, hepatosplenomegaly, mental retardation

101
Q

Which among the sugars has the fastest metabolism and highest yield of energy?

A

Fructose

102
Q

Which aldolase is used in glycolysis and what is the reaction catalyzed?

A

Aldolase A

Fru-1,6-BP to DHAP and glycerol-3-P

103
Q

Which aldolase is used in fructose metabolism and what is the reaction catalyzed?

A

Aldolase B

Fru-1-P to DHAP and glyceraldehyde

104
Q

Defect in fructokinase

A

Essential fructosuria

Benign

105
Q

Deficiency in aldolase B

A

Fructose intolerance

Autosomal recessive

Hypoglycemia, jaundicr, cirrhosis, vomiting

106
Q

Accumulates in classic galactosemia

A

Galactitol

Causing cataracts

107
Q

Mannose is an important component of

A

Glycoproteins

108
Q

Glucose to sorbitol is catalyzed by

A

Aldose reductase

109
Q

Sorbitol to fructose is catalyzed by

A

Sorbitol dehydrogenase

Found in seminal vesicles

110
Q

Other name of PPP

A

HMP shunt

111
Q

Products of PPP

A

NADPH and ribose-5-PO4
Fructose-6-P
Glyceraldehyde-3-P

112
Q

Substrate for PPP

A

Glucose-6-P

113
Q

T or F: In PPP, there is no consumption or production of ATP

A

True

114
Q

Rate limiting step and enzyme in PPP

A

Glucose-6-P dehydrogenase

Glu-6-P to 6-phosphogluconate

115
Q

Transketolases in the non-oxidative phase of PPP requires

A

Thiamine

116
Q

Used to diagnose thiamine deficiency

A

RBC transketolase activity

117
Q

The most important intermediate in PPP is

A

Ribose-6-PO4

118
Q

Removes H2O2

A

Reduced Glutathione (G-SH) catalyzed by glutathione peroxidase

Oxidizes glutathione when reacting with H2O2

119
Q

Glutathione peroxidase requires what cofactor?

A

Selenium

120
Q

Glutathione peroxidase is important in what cells?

A

RBCs

121
Q

Reduced glutathione is recreated using _________ and catalyzed by enzyme _______

A

NADPH

Glutathione reductase

122
Q

Deficiency in NADPH oxidase

A

Chronic Granulomatous Disease

Caused by catalase (+) bacteria

123
Q

Converts molecular oxygen into superoxide in leukocytes (especially neutrophils and macrophages) and used in the respiratory burst that kills bacteria

A

NADPH oxidase

124
Q

Liver glycogen can provide glucose in the absence of dietary glucose for how many hours?

A

10-18 hours

125
Q

4 Noncarbohydrate precursors of glucose

A

Lactate, pyruvate, glycerol, alpha-keto acids

Most important: glycerol, lactate, keto

126
Q

Gluconeogenesis occurs in what organs

A

During overnight fast

Liver - 90%
Kidneys- 10%

During prolonged fasting

Liver - 60%
Kidneys - 40%

127
Q

Amino acid that directly gives rise to pyruvate

A

Alanine

128
Q

Adipocytes cannot phosphorylate glycerol because the lack what enzyme

A

Glycerol kinase

129
Q

What process converts glucose to lactate?

A

Cori cycle ( in the exercising muscle)

Lactate is taken by the liver then converted to glucose

130
Q

Major sources of glucose during a fast

A

Amino acids

131
Q

Alpha ketoglutarate enters TCA cycle and form

A

Oxaloacetate

132
Q

Direct precursor of phosphoenolpyruvate

A

Oxaloacetate

133
Q

4 Compounds that gives rise to ketone bodies instead of glucose

A

Acetyl CoA
Acetoacetate
Leucine
Lysine

Due to irreversible reaction of puruvate dehydrogenase

134
Q

Converts PEP to pyruvate

A

Pyruvate kinase

Irreversible
Part of glycolysis

135
Q

Carboxylation of pyruvate by pyruvate carboxylase will form

A

Oxaloacetate

136
Q

Conversion of oxaloacetate to PEP is by

A

PEP carboxykinase

137
Q

Coenzyme needed by pyruvate carboxylase in carboxylation od pyruvate to OAA

A

Biotin

Binds to lysine residue

138
Q

Allosteric activation of pyruvate carboxylase is by

A

Acetyl CoA

Biochemistry (6 decks)

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