Carbohydrate Metabolism Flashcards

1
Q

What is metabolised in the intestine

A

Fats to Fatty Acids
Complex Carbohydrates to Monosaccharides
Proteins to Amino Acids

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2
Q

What metabolic processes happen in the cell cytoplasm

A

Conversion between pyruvate and lactate

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3
Q

What metabolic processes happen in the mitochondra

A

Formation of Acetyl Co-A
TCA Cycle
Most other metabolic activities

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4
Q

What are the energy carrying molecules

A

ATP, ADP, AMP

UTP, GTP, CTP, TTP

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5
Q

What is used for ATP storage

A

Creatine Phosphate

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6
Q

What are the electron carriers

A

NAD+, FAD, FMN, NADP+

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7
Q

What are the acyl group carriers

A

Co-ASH

Becomes Co-A when carrying acyl group

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8
Q

What does Glycogenesis convert

A

Glucose-6-phosphate to Glycogen

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9
Q

What does Glycogenolysis convert

A

Glycogen to Glucose-6-phosphate

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10
Q

What does Gluconeogenesis convert

A

Pyruvate to Glycose-6-phosphate

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11
Q

What does glycolysis convert

A

Glycose-6-phosphate to pyruvate

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12
Q

What does lipogenesis convert

A

Fatty Acids to Triacyglycerols

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13
Q

What does lipolysis convert

A

Triacyglycerols to Fatty Acids

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14
Q

What does FA synthesis convert

A

Acetyl Co-A to Fatty Acids

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15
Q

What does beta-oxidation convert

A

Fatty Acids to Acetyl Co-A

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16
Q

What are the consequences of eating dietry fibre

A
Adds bulk to faeces
Retains water in GIT
Speeds intestinal transit
Increases intestinal flora
Prevents diverticulitis and haemorrhoids
Slows digestion and absorption
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17
Q

How many carbons are there in monosaccharides

A

3-9

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18
Q

What are the types of hexoses

A

Glucose, Fructose, Galactose

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19
Q

What is the difference between wet monosaccharides and dry monosaccharides in structure

A

Wet - ring shape

Dry - chain structure

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20
Q

What are the types of pentoses

A

Ribose, Deoxyribose

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21
Q

What are disaccharides? Give some examples

A

Sucrose, Maltose, Lactose

2 monosaccharide subunits

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22
Q

What is sucrose made up of

A

Fructose and Glucose

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23
Q

What is maltose made up of

A

2 Glucose sugars

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24
Q

What is Lactose made up of

A

Glucose and Galactose

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25
Q

What are the three groups of polysaccharides

A

Starch
Glycogen
Cellulose

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26
Q

What are the types of starch

A

Amylose — alpha-1,4 bonds

Amylopectin — alpha-1,4 bonds and alpha-1,6 bonds

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27
Q

What is the structure of glycogen

A

alpha-1,4 bonds and alpha-1,6 bonds (more than in starch)

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28
Q

What is the structure of cellulose

A

beta-1,4 bonds

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29
Q

What is the membrane protein that absorbs maltooligosaccharides

A

Glucoamylase

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30
Q

What is the membrane protein that absorbs glucose

A

Glucose carrier

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31
Q

What is the membrane protein that absorbs alpha-limit dextrins

A

alpha-Dextrinase

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32
Q

What is the membrane protein that absorbs sucrose

A

Sucrase

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33
Q

What is the membrane protein that absorbs fructose

A

Fructose carrier

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34
Q

What is the membrane protein that absorbs gluucose

A

Glucose carrier

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35
Q

What is the membrane protein that absorbs lactose

A

Lactase

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36
Q

What is lactose intolerance caused by

A

Deficiency of lactase

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37
Q

What are the symptoms of lactose intolerance

A

Flatulence (bacteria digest lactose in gut)

Diarrhoea (water drawn into GIT)

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38
Q

What are the three possible fates of monosaccharides

A

Converted to fatty acids
Glycogen storage
Energy production (glycolysis)

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39
Q

Where are insulin independent glucose transporters found

A

Liver
Brain
RBCs
Pancreas

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40
Q

Where are insulin dependent glucose transporters found

A

All other tissues

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41
Q

How is glycogen phosphorylase inhibited?

A

Insulin causes it to be dephosphorylated

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42
Q

How is glycogen phosphorylase stimulated?

A

Glycagon, Adrenaline and Ca cause it to be phosphorylated

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43
Q

What does Glycogen phosphorylase convert? What assists it?

A

Converts: Glycogen —> Glycogen(n-1) + glucose-1-phosphate

It is assisted by De-branching enzyme

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44
Q

What does glucokinase do?

A

It converts Glucose to glucose-6-phosphate (In the liver and pancreas)

It uses one mole of ATP

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45
Q

What does hexokinase do

A

It converts Glucose to glucose-6-phosphate (in all tissues other than the liver and pancreas)

It uses one mole of ATP

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46
Q

Where is glucose-6-phosphatase found? What does it do?

A

Found in liver
Converts Glucose-6-phosphate to glucose
Releases an inorganic phosphate

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47
Q

What does branching enzyme do?

A

Forms alpha-1,6-glycosidic bonds from alpha-1,4-glycosidic bonds (which are made by glycogen synthase)

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48
Q

What is the rate limiting enzyme in glycogenesis

A

Glycogen Synthase

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49
Q

How is glycogen synthase activated?

A

insulin causes it to become dephosphorylated

50
Q

How is glycogen synthase inhibited?

A

Glycagon and Adrenaline (in liver) cause it to become phosphorylated

51
Q

What does glycogen synthase convert

A

UDP-glucose —> Glycogen (with an extra glucose)

52
Q

What activates Glucokinase?

A

Glucose
Insulin (increases amount of)

USES ONE ATP MOLECULE

53
Q

What is type 1 glycogen-storage disease caused by?

A

Glycose-6-phosphatase deficiency

54
Q

What is type 3 glycogen-storage disease caused by?

A

Glycogen Debranching enzyme deficiency

55
Q

What is type 5 glycogen-storage disease caused by?

A

glycogen phosphorylase deficiency in muscle

56
Q

Where does glycolysis take place?

A

All reactions take place in the cytosol

57
Q

What are the inputs of aerobic glycolysis

A

Glucose
2x ADP
2x Pi
2x NAD+

58
Q

What are the outputs of aerobic glycolysis

A
2 pyruvate
8 ATP (2 ATP + 2 NADH)
59
Q

What are the inputs of anaerobic glycolysis

A

Glucose
2 ADP
2 Pi

60
Q

What are the outputs of anaerobic glycolysis

A

2 lactate

2 ATP

61
Q

How are RBCs dependent on glycolysis

A

Totally dependent on anaerobic glycolysis – have no mitochondria

62
Q

How are muscle cells dependent on glycolysis

A

Dependent on aerobic and anaerobic glycolysis

63
Q

How is the brain dependent on glycolysis

A

Prefers aerobic glycolysis

64
Q

How are adipocytes dependent on glycolysis

A

Glycolysis needed for lipogenesis and cellular energy

65
Q

Where is glycokinase active

A

In the liver

66
Q

What decreases the activity of glucokinase

A

Glucagon

Adrenalin

67
Q

What inhibits the activity of hexokinase

A

It’s product, glucose-6-phosphate

68
Q

What does phosphofructokinase-1 do?

A

Converts Fructose-6-phosphate to Fructose-1,6-biphosphate

USES ONE MOLE OF ATP IN THE PROCESS

69
Q

What increases activity of phosphofructokinase-1

A

high AMP concentration
high concentration of glycolytic substrates
High concentration of insulin (indirectly)

70
Q

What decreases activity of phosphofructokinase-1

A

ATP
Citrate
Glucagon
Adrenalin

71
Q

What does pyruvate kinase do

A

Converts Phosphoenolpyruvate (PEP) to Pyruvate

MAKES ONE ATP IN THE PROCESS

72
Q

What increases activity of Pyruvate Kinase

A

fructose-1,6-biphosphate

Insulin

73
Q

What decreases activity of Pyruvate Kinase

A

ATP

Glucagon

74
Q

What does Lactate dehydrogenase do

A

Converts Pyruvate to Lactate

converts NADH to NAD+
Produces H- and H+ in the process

75
Q

What increases the activity of lactate dehydrogenase

A

High NADH

Low NAD+

76
Q

Overall, what stimulates glycolysis and what inhibits it

A

Insulin stimulates glycolysis
Glycagon inhibits glycolysis

This is unlike most other pathways

77
Q

What does the Pentose-phosphate Pathway convert overall?

A

Produces rbiulose-5-phosphate from glucose-6-phosphate

Produces NADPH from NADP+

78
Q

What is the rate limiting enzyme in the Pentose-phosphate pathway?

A

G6PD (Glucose-6-phosphate dehydrogenase)

79
Q

If cells are not active, what happens to the ribulose-5-phosphate

A

From 3 moles of ribulose-5-phosphate:

2 moles of Fructose-6-phosphate
1 mole of Glyceraldehyde-3-phosphate

80
Q

What is NADPH used for?

A
Making fatty acids, cholesterol (in liver) and steroid hormones
Reduces glutathionine (prevents oxidation-induced haemolysis)
81
Q

What can glucose be synthesised from?

A

Amino acids (in particular Aspartic Acid and Alanine)
Pyruvate
Lactate
Glycerol

82
Q

What does Fructose-1,6-biphosphotase do

A

Converts Fructose-1,6-biphosphate to Fructose-6-phosphate

Produces an inorganic phosphate in the process

83
Q

What activates Fructose-1,6-biphosphatase

A

glucagon

ATP

84
Q

What inhibits Fructose-1,6-biphosphatase

A

AMP

insulin

85
Q

What is the rate limiting enzyme of gluconeogenesis

A

Phosphoenolpyruvate Carboxy Kinase

86
Q

What activates phosphoenolpyrauvate Carboxy Kinase

A

Glucagon
Cortisol
Thyroid hormone

87
Q

What inhibits Phosphoenolpyruvate Carboxy Kinase

A

Insulin

88
Q

What does Phosphoenolpyruvate Carboxy Kinase do

A

Converts Oxaloacetate to Phosphoenolpyruvate

Converts GTP to GDP
Uses CO2

89
Q

What does pyruvate Carboxylase Do

A

Converts Pyruvate into Oxaloacetate

Uses ATP (converting it to ADP + Pi) and CO2

90
Q

What is Pyruvate Carboxylase activated by

A

Acetyl Co-A
Cortisol (causes increased levels)
Glucagon (cases increased levels)

91
Q

What is necessary for the functioning of Pyruvate Dehydrogenase (PDH)

A

Thiamine Pyrophosphate (from Vit B1)

92
Q

What does Pyruvate Dehydrogenase do?

A

Converts Pyruvate into Acetyl Co-A
Converts NAD+ into NADH
Releases CO2

93
Q

What inhibits Pyruvate Dehydrogenase

A

Acetyl Co-A
NADH
ATP

94
Q

What activates Pyruvate Dehydrogenase

A

Insulin
ADP
Ca

95
Q

What casuses beriberi

A

Thiamine deficiency

96
Q

What are the symptoms of beriberi

A

Increased plasma (lactate)
High output cardiac failure
Neurological symptoms

97
Q

What two groups of people is beriberi common in?

A

Alcoholics (Alcohol inhibits vitamin B1 absorption)

Populations that rely on polished rice

98
Q

What does Alcohol Dehydrogenase do

A

Converts ethanol to acetaldehyde

Converts NAD+ to NADH in the process

99
Q

What does Aldehyde Dehydrogenase do

A

Converts acetaldehyde to Acetic Acid

Converts NAD+ to NADH in the process

100
Q

What inhibits aldehyde dehydrogenase

A

Anabutase

101
Q

Where is aldehyde dehydrogenase active

A

In the mitochondria

102
Q

What can lead to acetaldehyde accumulation

A

Increased Alcohol Dehydrogenase Activity

Decreased Aldehyde Dehydrogenase Activity

103
Q

Why is acetaldehyde toxic

A

hangover symptoms
Vasodilation
Cellular damage

104
Q

What is the result of increased NADH from alcohol metabolism

A

Leads to conversion of pyruvate to lactate, inhibiting gluconeogensis and leading to hypoglycaemia

Decreased NAD+ in mitochondria -

  • slows TCA/krebs cycle
  • slows catabolism of fatty acids (leads to a fatty liver)
105
Q

What is the result of increased Acetyl Co-A from ethanol metabolism

A

Results in ketone body synthesis and production of fatty acids

106
Q

What happens in the Cori Cycle

A

Lactate is transported to liver to produce glucose

107
Q

What happens in the Alanine/Glucose-alanine cycle

A

Alanine is transported to the liver to produce glucose

108
Q

What does:
1: Low glucose uptake into cells
2: increased glucose release from cells
result from

A

Low Insulin

High Glucagon, Adrenalin and Cortisol

109
Q

What does:
1: High Glycogen synthesis
2: Low Gluconeogenesis
result from

A

High insulin

Low Glucagon, Adrenalin and Cortisol

110
Q

What does:
1: Low glycolysis
2: High glycogenolysis
result from

A

Low Insulin

High Glucagon, Adrenalin and Cortisol

111
Q

How is diabetes mellitus diagnosed?

A

1: Fasting blood glucose is above normal
2: Abnormal glucose tolerance test

112
Q

How is a glucose tolerance test performed?

A

1: Fast for 8 hours
2: Subject given 75g of glycose measured every 30 min for 3 hours

IN NORMAL PERSON, BLOOD GLUCOSE DROPS BACK DOWN AFTER 2 HOURS

113
Q

What is the metabolic profile of a type 1 diabetic

A

No insulin. Slightly increased glucagon (lack of insulin inhibition)

Increased blood glucose concentration:
1 - No insulin: Decreased uptake of glucose into cells
2 - Uninhibited glucagon: Increased glycogenolysis and gluconeogenesis

114
Q

What is the metabolic profile of a type 2 diabetic

A

Decreased ability for insulin to cause cellular response:

1: Decreased uptake of glucose into cells
2: Decreased inhibition of – glycogenolysis, gluconeogenesis

115
Q

What does Glucose-6-phosphate dehydrogenase do?

A

converts glucose-6-phosphate to 6-phosphgluconate
Uses H2O
Converts NADP+ to NADPH

116
Q

What is Fructose-1,6-biphosphate converted to

A

Converted to either Dihydroxyacetone Phorphate OR Glyceraldehyde-3-phosphate

117
Q

What is glyceraldehyde-3-phosphate converted to?

A

Conterted to 1,3-biphosphoglycerate
Converts ADP to ATP along the way

OR

Converted to 2,3-biphosphoglycerate

118
Q

What is 2,3-biphosphoglycerate converted to

A

Converted to 3-phosphoglycerate

Releases an inorganic phosphate

119
Q

What is the function of 2,3-biphosphoglycerate

A

Decreases haemoglobin affinity for O2

120
Q

What is the function of AST

A

Converts Aspartate to Oxaloacetate

121
Q

What is the function of ALT (Alanine Transaminase)?

A

Converts Alanine to pyruvate

122
Q

What is acetic acid converted to?

A

Acetyl Co-A

Uses Co-enzyme A
Uses ATP