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Gabe's Metabolism > Glucose: Tolerance curves, Absorption, Transporters, Storage and Synthesis > Flashcards

Glucose: Tolerance curves, Absorption, Transporters, Storage and Synthesis Flashcards

1
Q

How much energy is there in one molecule of ATP?

A

30.5kJ/mol

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2
Q

How much energy is there in one molecule of NADH?

A

220kJ/mol

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3
Q

What does metabolism link?

A

Breakdown (catabolism) of food to the synthesis of proteins and other biomolecules (anabolism)

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4
Q

What does anaerobic metabolism of glucose produce?

A

2ATP

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5
Q

What does aerobic metabolism of glucose produce?

A

32ATP

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6
Q

What is the fasting reserve of glucose?

A

Glycogen

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7
Q

What are the 2 major families of sugar?

A

Aldose and ketose

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8
Q

Which family do glucose and galactose belong to?

A

Aldose

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9
Q

Which family does fructose belong to?

A

Ketose

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10
Q

What are the 3 important GLUT transporters?

A

GLUT-1, GLUT-2 and GLUT-4

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11
Q

Where is GLUT-1 found?

A

Ubiquitous

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12
Q

Where is GLUT-2 found?

A

Liver and pancreas - important for responding to rising glucose

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13
Q

Where is GLUT-4 found?

A

In muscle and adipose tissue - key to diabetic rise in glucose because it is insulin responsive

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14
Q

What does anaerobic glycolysis produce?

A

Lactate

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15
Q

Why are red blood cells obligated to follow anaerobic metabolism?

A

Because they don’t have mitochondria

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16
Q

What does gluconeogenesis generate?

A

New glucose from glycerol or amino acids, never from fat

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17
Q

Which sugar correlates with increased obesity?

A

High fructose in processed food

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18
Q

What is ATP?

A

Adenosine triphosphate

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19
Q

What are enzymes using ATP called?

A

ATPases

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20
Q

What is the ∆G’˚ for ATP hydrolysis to ADP?

A

-30.5kJ/mol

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21
Q

What is always the cellular substrate for ATP?

A

Mg-ATP

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22
Q

What role does Mg2+ play in free ATP?

A

Removes charge propulsion between two O- atoms.

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23
Q

What is ∆G’˚ for PEP+ADP→pyruvate+ATP?

A

-31.4kJ/mol

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24
Q

What is ∆G’˚ for ADP+Pi→ATP+H2O?

A

+30.5kJ/mol

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25
Q

What is the ∆G’˚ for NADH oxidation to NAD-?

A

-220kJ/mol

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26
Q

What is the ∆E for NADH oxidation relative to the H-electrode?

A

-0.32V

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27
Q

What is the storage molecule for most of the electrons in metabolism?

A

NADH

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28
Q

What are the 3 stages to metabolism?

A

Stage 1: Acetyl-CoA production (Glycolysis)

Stage 2: Acetyl-CoA oxidation (Citric acid cycle)

Stage 3: Electron transfer and oxidative phosphorylation (Electron transfer chain)

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29
Q

What are glycosides?

A

Part sugar e.g. glycoprotein and cardiac glycosides

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30
Q

What do mono- and di-saccharides end in?

A

“‐ose”. e.g. glucose, maltose

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31
Q

How many carbons do monosaccharides have?

A

3‐7

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32
Q

Which configuration do Fischer projections of aldoses have?

A

D configuration

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33
Q

Which family do aldehyde sugars belong to?

A

Aldoses

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34
Q

What type of a sugar is glucose?

A

Aldehyde

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35
Q

What underlies circulatory problems leading to limb amputation and blindness in diabetes?

A

Glycation.

All amino groups, mostly in protein, are prone to this glycation.

Glycated blood vessels become brittle and prone to clots that stop the circulation.

Circulatory problems in diabetes can cause blindness, or gangrene with loss of feet.

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36
Q

What is the glycation reaction illustrated by?

A

Largely benign formation of haemoglobin‐A1C that acts as a diagnostic indicator of uncontrolled high glucose levels in blood.

The b‐subunits of Hb are particularly prone to glycation of the N‐termini.

A similar use is made of the fructosamine derivatives of serum albumin (half life 20 days).

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37
Q

Where are GLUT-4 transporters found?

A

Muscle

Fat

Heart

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38
Q

What does the insulin signal do?

A

Stimulates GLUT-4 to membrane

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39
Q

Where is Glucose-6-P found? What is its function?

A

Only liver and kidney.

Releases free glucose.

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40
Q

What is the intermediate between Glycogen and Glucose-6-P?

A

Glucose-1-P

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41
Q

Does glycolysis produce ATP aerobically or anaerobically?

A

Anaerobically

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42
Q

In which structures is glycolysis essential?

A

Red cells

Lens

Retina

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43
Q

What are the 2 phases to glycolysis?

A

Preparatory

Payoff

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44
Q

What is the reaction equation for glycolysis?

A

Glucose + 2NAD+ + 2ADP + 2Pi → 2pyruvate + 2NADH + 2ATP + 2H2O

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45
Q

What percentage of the 2.84MJ in a mole of glucose is captured as ATP?

A

2.1% (61kJ)

46
Q

Why do anaerobes consume much more glucose than aerobes?

A

Because they only receive 2ATP per molecule of glucose during anaerobic glycolysis.

47
Q

How many molecules of ATP per glucose do aerobes produce in glycolysis?

A

32

48
Q

What are the net products of glycolysis?

A

2 pyruvate

2ATP

2NADH

49
Q

Where in the cell does glycolysis occur?

A

In the cytosol

50
Q

What happens to every glycolysis metabolite except pyruvate?

A

Phosphorylated

51
Q

What prevents leakage of glycolysis metabolites through the cell membrane?

A

Negative charge

52
Q

How many ATPs are consumed in the preparatory phase of glycoloysis?

A

2

53
Q

What is created in the payoff phase of glycolysis?

A

4 Created in payoff phase

2 created in total

54
Q

What is the first step of glycolysis?

A

Conversion of glucose to glucose-6-phosphate by hexokinase

55
Q

What do the kinases do?

A

Transfer phosphate from ATP

56
Q

What is the structure of hexokinase?

A

Hexokinase: two domain enzyme exhibiting induced fit

Glucose binds to one domain, ATP to other

57
Q

What is the ∆G’˚ for conversion of glucose to glucose-6-phosphate?

A

-16.7kJ/mol

58
Q

What is the end product of glycolysis?

A

2 pyruvate

59
Q

Which two compounds have sufficiently high free energy of hydrolysis to be coupled to substrate level ATP synthesis?

A

1,3-BPG

PEP

60
Q

Which enzyme catalyses the second step of glycolysis?

A

Phosphohexose isomerase

61
Q

What happens in the second step of glycolysis?

A

Glucose-6-Phosphate converted to fructose-6-phosphate

62
Q

How does formation of the G-6P isomer F-6P proceed?

A

Via the linear conformatin of glucose-6-P, i.e. glucose-6-P must be in its linear conformation to be converted to fructose-6-phosphate

63
Q

Is step 2 of glycolysis regulated?

A

No

64
Q

Is the second step of glycolysis (G-6P to F-6P) a regulated step?

A

No

65
Q

What is the third step of glycolysis?

A

Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate

66
Q

What catalyses step 3 of glycolysis?

A

Phosphofructokinase-1

67
Q

When is phosphofructokinase active?

A

When cells have low ATP concentration

68
Q

Why is the third step of glycolysis an efficient step to regulate?

A

Because the high negative free energy change makes it functionally irreversible and commits metabolism to the glycolytic pathway.

69
Q

Which enzyme catalyses the reverse of step 3 in gluconeogenesis?

A

Fructose-1,6-bisphosphatase

70
Q

What does anaerobic metabolism in humans end in?

A

Lactate

71
Q

What does anaerobic glycolysis depend on?

A

Regenerating NAD+

72
Q

What converts pyruvate to lactate?

A

Lactate dehydrogenase

73
Q

What is generated as a product of anaerobic metabolism?

A

Lactate (lactic acid)

74
Q

Why is pyruvate reduced to lactate in anaerobic metabolism?

A

Because lactate is more energy rich than pyruvate

75
Q

What effect does creatine have?

A

Increases muscle stores of phosphocreatine, increasing the muscle’s ability to resynthesize ATP from ADP.

Phosphocreatine becomes ATP + creatine.

76
Q

What happens to blood lactate levels during vigorous exercise?

A

Increase

77
Q

What does the retina rely mostly on for ATP production?

A

Anaerobic glycolysis

There are few blood vessels in the fovea

78
Q

What do red blood cells rely on for ATP production? Why?

A

Anaerobic glycolysis.

Because mitochondria are lost during maturation

79
Q

What contributes to the background level of lactate in the blood?

A

Anaerobic glycolysis in red blood cells

80
Q

How many grams of glucose does the brain need per day?

A

120g

81
Q

Which carbon sources can be used in gluconeogenesis?

A

Lactate

Amino acids

Glycerol

82
Q

Where does lactate used in gluconeogenesis come from?

A

After exercise or anaerobic tissue (e.g. RBCs)

83
Q

Where do the amino acids used in gluconeogenesis come from?

A

Protein breakdown

84
Q

Where does glycerol used in gluconeogenesis come from?

A

Mobilisation of TAGs in adipose tissue

85
Q

What is the major carbon source for gluconeogenesis when starvation continues for several days?

A

Glycerol from mobilisation of TAGs in adipose tissue

86
Q

How does glycerol enter into gluconeogenesis if adipose issue lacks glycerol kinase?

A

It circulates to the liver to enter gluconeogenesis

87
Q

Are fatty acids glucogenic?

A

No, they are ketogenic

88
Q

What is the only difference between gluconeogenesis and glycolysis?

A

The 3 bypass reactions and the direction of the reaction.

89
Q

What does aerobic metabolism produce?

A

CO2 + H2O and 32 ATP per glucose

90
Q

What do fatty acids never make?

A

Glucose

91
Q

What is galactose?

A

4-epimer of glucose

92
Q

Where is galactose found?

A

Sphingolipid membrane strctures

Saccharide tags

Structural polymers

Lactose

93
Q

What is lactose?

A

β1-4 linked disaccharide of glaactose and glucose

94
Q

How is lactose created?

A

By an epimerase enzymes which needs energy supplied by UTP

95
Q

What does utilisation of lactose require?

A

Epimerisation of the galactose back to glucose

96
Q

What is galactosaemia?

A

Failure of epimerisation of galactose back to glucose

97
Q

What breaks lactose into 4-epimer galactose and glucose?

A

Lactase in the inestinal villi

98
Q

What happens if a galatosaemic infant is given milk?

A

Unmetabolised milk sugars build up and there’s damage to the liver, eyes, kidneys and brain

99
Q

What is galactosaemia a failure of?

A

Enzyme(s) in the galactose → glucose pathway

100
Q

Which side of the Fischer projections to D-series ketoses have their OHs on?

A

Right hand side

101
Q

When is a sugar a D-sugar?

A

When the highest number carbon with a chiral -OH is D-

102
Q

What are ketose sugars?

A

Ketones

103
Q

What is fructose?

A

The ketose form of glucose

104
Q

What is the sweetest of the common sugars?

A

Fructose

105
Q

What is fructose a breakdown product of?

A

Glycolysis

D-Glucose → a-D-fructofuranose

Catalysed by gluose isomerase

106
Q

How is fructose metabolised?

A

Liver forms fructose‐1‐phosphate which then undergoes aldolase splitting

107
Q

What is fructose half of?

A

Sucrose

108
Q

How is fructose implicated in obesity?

A

Does not elicit insulin release from the pancreas.

Fructose fails to increase the production of leptin from fat cells.

Both insulin and leptin act as signals to the brain to turn down the appetite and control body weight.

fructose does not appear to suppress the production of ghrelin, a hormone that increases hunger and appetite

109
Q

Which enzyme is used by industry to create fructose?

A

Isomerase

110
Q

What is aspartame?

A

Aspartyl-phenylalanine methyl ester

200x sweeter than sucrose

Gabe's Metabolism (5 decks)

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