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Metabolism > 2. Energy production I Carbohydrates, glycolysis, Pentose phosphate pathway > Flashcards

2. Energy production I Carbohydrates, glycolysis, Pentose phosphate pathway Flashcards

1
Q

What are the main monosaccharides obtained from our diet?

A

Glucose
Fructose
Galactose

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2
Q

What is table sugar made of?

A

Sucrose
Disaccharide
Glucose + fructose

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3
Q

What type of bonds do starch and glycogen have?

A

Alpha 1-4 glucose bonds

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4
Q

Where is amylase found?

A

Saliva

Pancreas - released into duodenum

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5
Q

What does amylase break down? And into what?

A

Polysaccharides Starch & glycogen

Into Monosaccharide glucose

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6
Q

What type of enzymes does the small intestine have?

A

Disaccharides

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7
Q

Name 4 disaccharides

A

Lactase
Sucrose
Pancreatic amylase
Isomaltase

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8
Q

What type of bonds does cellulose contain?

A

Beta 1-4 bonds

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9
Q

What type of food groups is cellulose particularly found in ?

A

Dietary fibre

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10
Q

What is the difference between amylase found in saliva and amylase found in pancreas ?

A

Saliva - breaks down starch/glycogen to dextrins (oligosaccharides)

Pancreas - breaks down starch/glycogen to glucose
Include disaccharides

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11
Q

What is the cause of primary lactase deficiency ?

A

Absence of lactase persistence allele

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12
Q

Does primary lactase deficiency occur in adults or children?

A

Adults

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13
Q

What causes lactose intolerance ?

A

Deficiency of enzyme lactase

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14
Q

What types of food should lactose intolerant patients avoid?

A

Milk
Cheese
Yogurt
Cream

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15
Q

Which type of lactase deficiency is reversible?

A

Secondary lactase deficiency

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16
Q

What causes secondary lactase deficiency ?

A

Injury to small intestine

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17
Q

Can secondary lactase deficiency occur in infants or adults?

A

Both

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18
Q

What is coeliac disease?

A

Inflammation of small intestine

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19
Q

What causes coeliac disease?

A

Adverse reaction to gluten

Gluten is a dietary protein found in 3 types of cereal (wheat, barley, rye)

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20
Q

What is crohns disease?

A

Long term inflammation of the lining of the digestive system.
Anywhere in alimentary canal

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21
Q

What two main symptoms does gastroenteritis cause?

A

Vomiting

Diarrhoea

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22
Q

What are some causes of gastroenteritis ?

A

Food poisoning

Noravirus

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23
Q

Name 4 conditions that can result in secondary lactase deficiency ?

A

Gastroenteritis
Crohn’s disease
Coeliac disease
Ulcerative colitis

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24
Q

What is the most rare form of lactase deficiency ? And what causes it ?

A

Congenital lactase deficiency
Autosomal recessive mutation of lactase gene
Cannot digest breast milk

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25
Q

What are the symptoms of lactose intolerance

A 
Bloating 
Vomiting
Diarrhoea 
Rumbling stomach 
Flatulence (gas accumulation in alimentary Canal )
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26
Q

How does glucose enter from the intestinal lumen into the apical side of the intestinal epithelial cell?

A 
Secondary active transport 
Via SGLT1 (Symporter with sodium)
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27
Q

How does glucose enter the bloodstream from the basolateral end of the intestinal epithelial cell ?

A

Via transport protein GLUT 2

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28
Q

Which transporter does galactose enter blood through in intestine ?

A

Glut 2

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29
Q

How do monosaccharides go from blood into cells?

A

Facilitated diffusion via GLUT 1-5 transport proteins

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30
Q

Where are GLUT 1 transport proteins found?

A

Fetal tissue
Erythrocytes
Blood brain barrier

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31
Q

Where are GLUT 2 transport proteins found?

A

Kidney
Liver
Pancreas beta cells
Small intestine

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32
Q

Where are GLUT 3 transport proteins found?

A

Neurones

Placenta

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33
Q

Where are GLUT 4 transport proteins found?

A

Adipose
Striated muscle
(Insulin regulated)

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34
Q

Where are GLUT 5 transport proteins found?

A

Spermatozoa

Intestine

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35
Q

Which cells can only metabolise glucose?

A

Erythrocytes
Neutrophils
Innermost cells of kidney medulla
Lens of eye

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36
Q

What fuels of energy can the brain use?

A

Glucose

Ketone bodies

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37
Q

When does the brain use ketone bodies?

A

Times of starvation

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38
Q

What is glycolysis?

A

Intracellular Pathway in which monosaccharides get converted to pyruvate

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39
Q

What are the two phases of glycolysis ?

A

Investment

Payback

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40
Q

What is produced at the end of glycolysis per glucose molecule?

A

2 molecules of pyruvate (each 3 carbon)
2 NADH
2 net ATP

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41
Q

How many carbons does one molecule of pyruvate have at the end of glycolysis?

A

3

42
Q

Where does glycolysis take place in a cell?

A

Cytoplasm

43
Q

Glycolysis is exergonic, what does this mean?

A

Accompanied by release of energy

44
Q

Which enzyme has a lower affinity for glucose, hexokinase or glucokinase ?

A

Hexokinase

45
Q

Which enzyme is inhibited by glucose 6 phosphate?

A

Hexokinase

46
Q

Which tissue is hexokinase found in?

A

All

47
Q

Which tissue is glucokinase found in?

A

Liver

48
Q

What do hexokinase & glucokinase do?

Is energy required?

A

Glucose to glucose 6 phosphate.

1 molecule of ATP required

49
Q

What does phosphofructokinase-1 do?

Does it require energy?

A

Fructose-6-P to Fructose 1,6-bis-P

Uses 1 molecule of ATP

50
Q

In the investment phase which enzymes require ATP and what are the reactions they each catalyse?

A

1) hexokinase/glucokinase : glucose to glucose-6-P

2) phosphofructokinase-1 : fructose-6-P to fructose-1,6-bis-P (COMMITTING STEP - ONLY WAY NOW IS GLYCOLYSIS)

51
Q

What is substrate level phosphorylation?

A

Converting ADP - ATP

52
Q

What is gluconeogenesis ?

A

Converting pyruvate to glucose

53
Q

In glycolysis how many irreversible steps are there?

A

3

54
Q

What does pyruvate kinase do?

Does it require energy?

A

Phosphoenolpyruvate to pyruvate

No releases 1 molecule of ATP

55
Q

Do cancer cells have a higher rate of glycolysis?

A

Yes

56
Q

What is 2-18-F-2-deoxyglucose (FDG)?

What is it used for ?

A

RADIOACTIVE MODIFIED HEXOKINASE SUBSTRATE

Imaging cancer cells with positron emission tomography

57
Q

In glycolysis what is the key regulator ? And in what 2 ways is it regulated ?

A

Phosphofructokinase

  • allosteric regulation & hormonal regulation
58
Q

Where does allosteric regulation of phosphofructokinase occur?

A

Muscle

59
Q

Where does Hormonal regulation of phosphofructokinase occur?

A

Liver

60
Q

What inhibits phosphofructokinase?

A

ATP (MUCLE) (ALLOSTERIC)

INSULIN (LIVER) (HORMONAL)

61
Q

What stimulates phosphofructokinase ?

A

AMP (MUSCLE) (ALLOSTERIC)

GLUCAGON (LIVER) (HORMONAL)

62
Q

WHICH ENZYME CAN BE REGULATED Hexokinase or glucokinase? By what?

A

Hexokinase

Inhibited by glucose-6-P

63
Q

What regulates pyruvate kinase?

A

Stimulated by high insulin, low glucagon

64
Q

How is glycolysis regulated ?

A

1) phosphofructokinase (stimulated: AMP, Insulin. Inhibited: ATP, glucagon)
2) hexokinase (inhibited: glucose-6-P)
3) pyruvate kinase: (stimulated: high insulin, low glucagon)
4) high NADH, low NAD+ = INHIBITION

65
Q

WHAT TWO IMPORTANT INTERMEDIATES ARE FORMED FROM GLYCOLYSIS?

A

2,3- BISPHOSPHOGLYCERATE -

GLYCEROL PHOSPHATE

66
Q

What is 2,3-Bisphosphoglycerate?

A

Produced in erythrocytes
Regulates haemoglobin
Promotes o2 release from Hb

67
Q

What is the function of glycerol phosphate?

A

Needed for Triglyceride and phospholipid biosynthesis

Produced in adipose via glycolysis

68
Q

What does the enzyme bisphosphoglycerate mutase do ?

A

Catalyse

1/,3-bis phosphoglycerate to 2,3-bis phosphoglycerate

69
Q

What does glycerol 3-phosphate dehydrogenase do?

A

Catalyse

DIHYDROXYACETONE-P TO GLYCEROL PHOSPHATE

70
Q

How many molecules of NADH is produced per glucose?

A

2

71
Q

Which enzyme converts pyruvate into lactate & lactate into pyruvate ?

A

Lactate dehydrogenase

72
Q

When would anaerobic respiration be used by a cell?

A
  • no mitochondria (RBC)
  • reduced blood supply
  • little o2 available
73
Q

What happens to lactate that travels to the liver?

A
  • some of it used as an energy source and converted back to pyruvate to be oxidised and release energy
  • most of it converted back to pyruvate and undergoes gluconeogenesis.
74
Q

What is gluconeogeneis?

A

Metabolic pathway that results in generation of glucose from certain non-carbohydrate carbon substrates (eg lactate)

75
Q

What happens to lactate that is formed by a cell in anaerobic respiration?

A

Travels in blood to

1) heart - converted back to pyruvate and used as energy source
2) liver - converted back to pyruvate and undergoes gluconeogenesis.

76
Q

In anaerobic respiration after glycolysis what happens to the NADH?

A

Reduced back to NAD+ via lactate dehydrogenase

77
Q

What is the normal concentration of lactate in the blood?

A

<1mM

78
Q

What is the plasma concentration of lactate in hyperlactaemia?

A

2-5mM and

79
Q

What is the plasma concentration of lactate in lactic acidosis ?

A

> 5mM

80
Q

At what level of lactate can the kidneys not cope with the plasma concentration of lactate?

A

> 5mM

Lactic acidosis

81
Q

What is milk sugar made from?

A

Lactose = galactose + glucose

82
Q

What is galactosaemia?

A

Autosomal recessive disorder

Reduced ability to metabolise galactose

83
Q

Galactosaemia can be caused by deficiency in which 3 enzymes?

A
  • galactokinase
  • uridyl transferase
  • UDP - galactose epimerase
84
Q

What does galactokinase do?

A

Galactose to galactose-1P

85
Q

What does uridyl transferase do?

A

Galactose-1P to glucose-1P

86
Q

What does UDP-galactose epimerase do?

A

Galactose-1P to UDP-galactose

Product can be converted to glycogen for storage

87
Q

Where is fructose metabolised ?

A

Liver

88
Q

What does the enzyme Fructokinase do?

Is energy required?

A

Fructose to Fructose-1P

Yes 1 molecule of ATP

89
Q

What does the enzyme Aldolase do?

A

Fructose-1P to glyceraldehyde-3-p (which can undergo glycolysis)

90
Q

Which enzyme is missing in essential fructosuria ?

A

Fructokinase

91
Q

What are the clinical signs of essential fructosuria?

A

There are none

92
Q

Which enzyme is missing in fructose intolerance?

A

Aldolase

93
Q

What organ can be damaged in fructose intolerance ? Why?

A

Liver due to build up of fructose-1P

94
Q

What is the treatment for fructose intolerance?

A

Remove fructose from diet

95
Q

What is the function of the pentose phosphate pathway?

A

1) produce NADPH

2) produce pentose (C5) sugars needed for synthesis of nucleotides, DNA & RNA

96
Q

How much ATP is produced from the pentose phosphate pathway ?

A

None

97
Q

Which molecule does the pentose phosphate pathway start with?

A

Glucose - 6- phosphate

98
Q

What is the rate limiting enzyme in the pentose phosphate pathway?

A

Glucose 6 phosphate dehydrogenase

99
Q

What is NADPH required for?

A
  • regeneration of glutathione (GSH) - ANTIOXIDANT
  • FATTY ACID & STEROID BIOSYNTHESIS
  • REDUCING POWER FOR BIOSYNTHESIS
100
Q

WHAT IS GLUTATHIONE (GSH)?

A

Antioxidant

Metabolism (4 decks)

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