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Flashcards in MCM - Carb Metabolism Deck (182):
1

What chemical reaction do all cells carry out for energy?

Glycolysis

2

What are 3 major monosaccharides that can be used in Glycolysis

Glucose, Fructose, and Galactose

3

Which cell group can only use Glycolysis

Red Blood Cells

4

Whats the brain's primary source of energy when in "fed" state

Glycolysis

5

How does Glucose enter a cell

Through the use of GLUT transporters; facilitated diffusion

6

How many types of GLUT are there for uptake of solely Glucose

GLUT 1, GLUT 2, GLUT 3, GLUT 4

7

GLUT 1 characteristics

Found everywhere, but high concentration in RBC's and Brain; high affinity

8

GLUT 2 Characteristics

Main transport in liver; low affinity. But picks up any source of glucose

9

GLUT 3 Characteristics

Main transporter in neurons; High Affinity

10

GLUT 4 Characteristics

Present in skeletal muscle, heart, adipose tissue; Insulin Dependent

11

Where is GLUT 4 located in the cell

Sequestered in vesicles until insulin is bound

12

What enables GLUT 4

Binding of insulin, which releases GLUT 4 to the plasma membrane

13

Basic Steps of Glycolysis

1 molecule of glucose -> generate 2 molecules of pyruvate; generate 2 ATP; generate 2 NADH

14

Is glycolysis Anaerobic or Aerobic

Anaerobic

15

Where does glycolysis occur in the cell

Cytoplasm

16

First Part of Glycolysis

Phosphorylation of Glucose to Glucose-6 Phosphate by Hexokinase/Glucokinase

17

What main energy source does Glycolysis require

One molecule of ATP

18

Differences between Hexokinase and Glucokinase

Hexokinase is the general enzyme; glucokinase is specific to the liver and pancreatic Beta cells

19

What is the Rate Limiting Step of Glycolysis

The phosphorylation of Fructose-6 Phosphate to Fructose 1,6-biphosphate

20

What enzyme performs the first reaction of Glycolysis

Hexokinase/Glucokinase

21

What enzyme performs the Rate Limiting Step of Glycolysis

Phosphofructokinase-1; PFK-1

22

What does Phosphofructokinase do

Phosphorylates Fructose 6-Phosphate to Fructose 1,6-biphosphate

23

Does Phosphofructokinase use ATP

Yes

24

What does the phosphorylation of G3P produce

One NADH; no use of ATP

25

Where does the first pay off of Glycolysis occur

When G3P is phosphorylated

26

What is the second pay off stage of Glycoysis

Conversion of 1,3-BPG to 3-PG; 2 ATP created

27

What is the third and final pay off stage of Glycolysis

Formation of Pyruvate from Pyruvate Kinase; 2 ATP created; also irreversible

28

What are the 3 pay-off stages of Glycolysis

1. Phosphorylation of G3P; 1 NADH
2. Conversion of 1,3BPG to 3-PG; 2 ATP
3. Formation of Pyruvate; 2 ATP

29

What enzyme phosphorylates Glucose to Glucose 6-Phosphate

Hexokinase (general)/ glucokinase (liver and pancreas)

30

What enzyme Phosphorylates Fructose 6-P to Fructose-1,6- Biphosphate

Phospofructokinase-1

31

Which enzymes in Glycolysis use ATP

Phospofructokinase-1 and Hexokinase (general)/ glucokinase (liver and pancreas)

32

Which enzyme takes 1,3-BPG to 3-phosphogylcerate

Phosphoglycerate Kinase

33

Which enzyme takes Phosphoenolpyruvate to Pyruvate

Pyruvate Kinase

34

Which enzymes in Glycolysis produce ATP via their reaction

Pyruvate Kinase and Phoshoglycerate Kinase

35

Which enzyme takes Glyceraldehyde 3-P to 1,3-Bisphosphoglycerate

Glyceraldehyde 3-P dehydrogenase

36

Which enzyme in Glycolysis produces one NADH

Glyceraldehyde 3-P dehydrogenase

37

What are the three irreversible steps of Glycolysis

1. Hexokinase/Glucokinase (Trap Glucose)
2. Phosphofructokinase (Add another Phosphate)
3. Pyruvate Kinase (Split the 6 Carbon molecule to two 3 carbon molecules)

38

Hexokinase has a low or high affinity

High affinity; binds all glucose

39

Glucokinase has a low or high affintiy

Low affinity

40

What is Hexokinase inhibited by

G6P; the product of this enzymes action

41

What is Glucokinase inhibited by

Nothing really, but Glucagon

42

When is Glucokinase most active

High Glucose

43

Insulin induces the synthesis of

Glucokinase

44

Glucagon inhibits the synthesis of

Glucokinase

45

PFK-1 Activators

AMP, Fructose 2,6-Bisphosphate

46

What makes Fructose 2,6-Bisphosphate

PFK-2

47

PFK-1 Inhibitors

ATP, Citrate (TCA Cycle)

48

When is PFK-1 Activated; when its phosphorylated or dephosphorylated

Dephosphorylated

49

Hormonal Regulation of PFK-1

Glucagon Inhibits; Insulin Activates

50

What activates Pyruvate Kinase

Fructose 1,6-Bisphosphate and Glucagon

51

What inhibits Pyruvate Kinase

ATP, Alanine, and Glucagon

52

High Insulin Effect on Pyruvate Kinase

Stimulates protein phosphatase, dephosphorylation of PK, activate

53

High Glucagon Effect on Pyruvate Kinase

cAMP activates PKA, phosphorylation, PK Inhibited

54

Glucose 6-Phosphate Use in Other Pathways

Precursor for the PPP
Can be converted to Glucose 1-Phosphate
{used in galactose metabolism, glycogen synthesis, ironic acid pathway}

55

Glucose 6-Phosphate's Outcome in the Pentosephosphate Pathway

Ribose and NADPH

56

Use of Ribose

For DNA Synthesis

57

Use of NADPH

Resythesizing Glutathione, a Selenium co-factor for getting rid of Hydrogen Peroxide

58

What are some fates of Pyruvate

1. Reduced to lactate; to regenerate NAD+ in anaerobic conditions
2. Oxidized in TCA cycle to Acetyl CoA and the CO2
3. Converted to Alanine; used in gluconeogenesis and protein synthesis
4. Converted to ethanol

59

Disorders of Glycolysis effect what two areas the most

The brain and the RBC's

60

What do disorders of glycolysis usually cause

hemolytic anemia; because RBC's cannot maintain there molecular gradients

61

Which enzyme is most affected in glyosis disorders

Pyruvate Kinase (95%)

62

What are the 2 types of Diabetes

1. Type 1- autoimmune disorder affecting the Beta Cells of the Pancreas in the Langhorn area
2. Type 2: Insulin resistance, usually caused by being extremely overweight

63

Other Potential causes of Diabetes than obesity

mutations, aberrant conversion of proinsulin to mature insulin, defective insulin receptor

64

What is the normal blood glucose range; fasting

70-100 mg/dL

65

What is the normal blood glucose range; fed

<140 mg/dL

66

Prediabetic glucose range; fasting

100-125 mg/dL

67

Prediabetic glucose range; fed

>125 mg/dL

68

Tarui Disease

Deficient in PFK-1; least common Glycolysis Disorder; exercise induced muscle cramps and weakness

69

How much glucose does the brain need in one day

120 grams

70

How much glucose is present in body fluids

20 grams

71

How much glycogen is readily available in the body

190 grams

72

How long can glycogen stores supply the body

About one day without eating glucose

73

Where does Gluconeogenesis Occur

Liver, Kidney, and Small Intestine

74

What does Gluconeogenesis accomplish

converts pyruvate back to glucose

75

What can be fed into gluconeogenesis

lactate, amino acids, and glycerol

76

What are the two enzymes where gluconeogenesis converts (2x) pyruvate

Pyruvate Carboxylase and PEP Carboxylase

77

What enzyme does Gluconeogenesis use to bypass PFK-1 process

Fructose 1,6-bisphosphatase

78

What enzyme does Gluconeogenesis use to bypass hexokinase/glucokinase

glucose 6-phosphatase

79

Positive Regulators of Gluconeogenesis

Glucagon, citrate, cortisol, thyrozine, acetyl CoA

80

Positive regulators of Glycolysis

Glucose, insulin, AMP, Fructose 2,6-BP, Fructose 1,6-BP

81

Negative regulators of Gluconeogenesis

ADP, AMP, Fructose 2,6-BP`

82

Negative regulators of Glycolysis

Glucagon, ATP, citrate, Glc 6-P, Fructose 6-P, Alanine

83

4 enzymes that gluconeogenesis uses to bypass glycolysis irreversible steps

1. Pyruvate Carboxylase
2. Phosphoenolpyruvate Corboxykinase
3. Fructose 1,6-BP
4. Glucose 6-phosphatase

84

What is Pyruvate Carboxylase

Mitochondrial Enzyme; activated by acetyl CoA and Cortisol

85

Can Oxaloacetate leave the mitochondria

No; its impermeable

86

How does Oxaloacetate need to be altered to leave mitochondria

Reduced to malate

87

How is Malate changed once it leaves the mitochondria

Re-Oxidized to Oxaloacetate

88

PEP Carboxykinase

Decarboxylation and phosphorylation of Oxaloacetate to PEP

89

What activates PEP Carboxykinase

Cortisol, Glucagon, Thyroxine

90

What is the Rate Limiting step of Gluconeogenesis

Fructose 1,6-Bisphosphatase

91

What is Fructose 1,6-Bisphosphatase Activated by

Cortisol and Citrate

92

What is Fructose 1,6-Bisphosphatase Inhibited by

AMP and F 2,6-BP

93

What is the last step of Gluconeogenesis

Dephosphorylation of Glucose 6-Phosphate to Glucose

94

What enzyme takes Glucose 6-Phosphate to Glucose

Glucose 6-Phosphatase

95

What activates Glucose 6-Phosphatase

Cortisol

96

Where is Glucose 6-Phospatase found

Liver, Kidney, Small Intestine and Pancreas

I.E. Where Gluconeogenesis occurs

97

Where in the cell is Glucose 6-Phosphatase found

The lumen of the ER

98

How does glucose 6-P get into the lumen of the ER to get to Glucose 6-Phosphatase and get back glucose back out

G6P Transporter
and
GLUT7 transporter back into the cytoplasm

99

Cori Cycle Process

2 lactate from the muscle transported to the liver
Once in the liver 2 lactate into 2 pyruvate
Once 2 pyruvate you get Glucose with a 4 ATP investment via Gluconeogenesis

100

Name Four Precursors to Gluconeogenesis

1. Glycerol (Carb)
2. Propionate (from odd-numbered fatty acids)
3. Alanine (Protein Degradation)
4. Amino Acids (Protein Degradation)

101

Name two other sugars that can go into Gluconeogenesis

1. Galactose
2. Fructose

102

Fructose 1,6-BP Deficiency Consequences

Cannot have the payoff of Gluconeogenesis

103

Von Gierke Disease

Mutations in the catalytic site in GSD 1a
Present with hepatomegaly due to buildup of glycogen in the liver

104

Sucrose Structure

Fructose and Glucose

105

What is Sucrose Cleaved by

Sucrase

106

Lactose Structure

Galactose and Glucose

107

What is Lactose cleaved by

Lactase

108

Which GLUT Transporter uptakes Fructose

GLUT 5

109

SGLT1 uptakes which two sugars

Galactose and Glucose

110

Franconi-Bickel Syndrome; Overall effect

GLUT 2 mutation; failing to absorb galactose, glucose, and fructose

111

Location of GLUT 2 Tranporter

Liver, Pancreatic Beta Cells, Enterocytes, and renal tubular cells

112

What process takes Glucose to Fructose

The Polyol Pathway

113

What is the Polyol Pathway

Glucose reduced to Sorbitol, Sorbitol oxidized to Fructose

114

What two enzymes are utilized in the Polyol Pathway

Aldose Reductase and Sorbitol Dehydrogenase

115

Cells lacking Sorbitol Dehydrogenase allow build up of sorbital triggering what

Cataracts

116

Fructose Caviet in entering Glycolysis

Can by-pass PFK-1, the rate-limiting step of Glycolysis
This leads to excess Pyruvate, furthering to storage of Fatty Acids into Triacylglycerols, leading to excess Fat

117

High Fructose Corn Syrup Effect

Can bypass PFK-1 and be stored as fat easier

118

Deficiency of Galactokinase leads to

Build up of Galacitol; leading to cataracts

119

Deficiency in Glucose 1P uridyltransferase

Leads to accumulation of Galacitol because of the side reaction that takes place

120

What does the Pentose Phosphate Pathway Produce

1. Sugar needed for DNA and RNA formation
2. NADPH; used to remake Glutathione

121

Where does the P.P.P. take place

Cytosol

122

What does G6P Dehydrogenase produce from the Pentose Phosphate Pathway

NADPH

123

What is the rate limiting step of the P.P.P.

G6P Dehydrogenase

124

G6PD Deficiency

Accumulation of hydrogen peroxide, leads to hemolytic anemia

125

Which Part of the P.P.P. is irreversible

The Oxidative Phase

126

What does the Oxidative Phase of the P.P.P. produce

NADPH and Ribulose 5-P

127

What Part of the P.P.P. is reversible

The Non-Oxidative Phase

128

What does the Non-Oxidative Phase Produce

Several Metabolites that can go into glycolysis and gluconeogenesis

129

When is the Oxidative side of the P.P.P. favored

When cells are rapidly dividing; in need of Ribulose 5-P

130

When there is a high demand for NADPH what does the P.P.P. do

Non-Oxidative products channeled into gluconeogenesis for re-entry into the P.P.P. Oxidative Pathway

131

Where is an area where P.P.P. activity is very high

Phagocytic Cells

132

What kind of chain is produced with the alpha 1,4

Straight chain

133

What kind of chain is produced with the alpha 1,6

Branches

134

Which end of glycogen is free to react?

The non-reducing end

135

Which end of glycogen is not free to react

The reducing end

136

What is the hallmark of the non-reducing end

An OH- group at Carbon 4

137

Where does Glycogen Store

The Liver and Muscle

138

How is glycogen stored inside the liver and muscle

Inside granules; containing the enzymes needed for glycogen metabolism

139

What is the function of Liver Glycogen

To regulate blood glucose

140

What is the function of Muscle Glycogen

To provide a reservoir of glucose for physical activity

141

What is the first step of Glycogenesis

Trapping and Activation of Glucose; hexokinase/Glucokinase phosphorylyze glucose in liver and muscle cells (in the cytosol of the respective cells)

142

What is the rate limiting step of Glycogensis

Glycogen Synthase; adds UDP-Glucose to non-reducing end of glycogen chain

143

What branches the growing glycogen chain

At about 11 residues a fragment is broken off and the reattached elsewhere to with an alpha 1,6 chain via branching enzyme

144

How does branching effect the solubility of glycogen

Increases the solubility as branching is increased

145

What is the rate limiting step of Glycogenolysis

Glycogen Phosphorylase

146

What does Glycogen Phosporylase do

Catalyzes the cleavage of glucose residues as a G1P from the non-reducing end

147

How does the alpha 1,6 bond break

With debranching enzyme, adding the 3 residues back to the straight chain, cleaving the last alpha 1,6 bond that is left to release free glucose

148

Ratio of Glu-1-P to Glu

10:1

149

Fate of Liver Glu-1-P

converted to Glu-6-P and then to Glu. Free glucose released to blood

150

Fate of Muscle Glu-1-P

Myocytes and cardiac myocytes lack glucose-6-phosphatase. So they use the Glu-1-P to generate energy via glycolysis and the TCA cycle

151

What are 2 important reasons to regulate glycogen metabolism

1. Maintain Blood Sugar
2. Provide Energy to Muscle

152

What are the 2 Key enzymes in regulating glycogen metabolism

1. Glycogen Synthase
2. Glycogen Phosphorylase

153

What does Glycogen Synthase do

makes alpha 1,4 links and is the rate limiting step of glycogensis

154

What does Glycogen Phosphorylase do

Cuts the alpha 1,4 links and the is the rate limiting step of glycogenolysis

155

When is Glycogen Synthase active

When it is in the Dephospho form

156

When is Glycogen Phosphorylase Active

When it is in the Phospho form

157

When is Glycogen Synthase Inactive

When it is in the Phospho Form

158

When is Glycogen Phosporylase Inactive

When it is in the Depospho Form

159

In which state, fed or fasting, is Glycogenesis favored

Fed

160

In which state, fed or fasting, is Glycogenolysis favored

Fasting

161

Which state is favored while exercising, glycogenolysis or glycogenesis

Glycogenolysis

162

What are the four key proteins involved in Insulin Regulation

1. GLUT 4; insulin sensitive GLUT transporter
2. Protein Kinase B (PKB)
3. Protein Phosphatase 1 (PP1)
4. Glycogen Synthase Kinase 3 (GSK 3)

163

Effect of Insulin Binding on Glycogen Synthase

Binds, excites PKB. PKB excites PP1 which phosphorylates Glycogen Synthase activating it

164

Effect of Insulin Binding on Glycogen Phosphorylase

Insulin binds, excites PKB. PKBB Excites PP1. PP1 inhibits Pyruvate Kinase and dephosphorylates Glycogen Phosporylase

165

Type 2 Diabetes Blood Criteria

Normal: 70-100mg fasting; <140mg fed
PreDiabetic: 100-125mg fasting; >140 fed
Diabetic: >126mg fasting; >199mg Fed

166

Key Enzymes and secondary messengers of Glucagon Regulation

G Protein
Adenylate Cyclase and cAMP
Protein Kinase A
Protein Phosphatase 1
Phosphorylase Kinase

167

Net Result of Insulin Binding

Glycogen is stored

168

Net Result of Glucagon Binding

Glycogen is broken down for glucose

169

Effect of Glucagon Binding on Glycogen Synthase

Phosphorylates Glycogen Synthase; deactivating it

170

Effect of Glucagon Binding on Glycogen Phosphorylase

Dephosphorylates Glycogen Phosphorylase; activating it

171

Effect of Epinephrine binding to muscle or liver during exercise

Same as Glucagon

172

Glycogen Storage Disease; Genetic Traits

Autosomal Recessive

173

Glycogen Storage Diseases

1. Glycogen Synthase Defective
2. Von Gierke Disease
3. Pompe Disease
4. Cori Disease
5. Anderson Disease
6. McArdle Disease
7. Hers Disease

174

What enzyme is defective in Glycogen Synthase Defect

Glycogen Synthase

175

What enzyme is defective in Von Gierke Disease

Glucose 6-Phosphatase

176

What enzyme is defective in in Pompe Disease

Acid Maltase

177

What enzyme is defective in Cori Disease

Debranching Enzyme

178

What enzyme is defective in Anderson Disease

Glucosyl (4:6) Transferase

179

What enzyme is defective in McArdle Disease

Muscle Glycogen Phosphorylase

180

What enzyme is defective in Hers Disease

Liver Glycogen Phosphorylase

181

Difference between McArdle Disease vs. Hers Disease

McArdle: in Muscle GP; muscle form of isozyme is activated by AMP, Ca-CaM, and G Actin
Hers: in Liver GP; inactivated by free glucose and unaffected by AMP

182

G-3-P and DHAP have an equilibrium; DHAP can also go

Into FA Synthesis and TAG Synth