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Semester 2-MEH > Session 1-Energy Production I > Flashcards

Session 1-Energy Production I Flashcards

1
Q

What is stage 1 of metabolism of dietary carbs?

A

Breakdown to building blocks

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2
Q

Which enzyme is present in saliva to digest carbs and which reaction does it catalyse?

A

Amylase

Starch/glycogen -> dextrins

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3
Q

Which enzyme is present in the pancreas to digest carbs?

A

Amylase

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4
Q

Which enzymes are present on the brush border membrane of epithelial cells?

A

Lactase
Sucrase
Pancreatic amylase
Isomaltase

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5
Q

What causes primary lactase deficiency?

A

Absence of lactase persistence allele

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6
Q

True or false: primary lactase deficiency occurs in children and adults

A

FALSE - only adults

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7
Q

What causes secondary lactase deficiency?

A 
Injury to small intestine: 
Gastroenteritis 
Coeliac disease
Crohn's disease 
Ulcerative colitis
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8
Q

True or false: secondary lactase deficiency occurs in both infants and adults

A

TRUE

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9
Q

What is congenital lactase deficiency?

A

Autosomal recessive defect in lactase gene

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10
Q

What are the symptoms of lactose intolerance?

A 
Bloating/cramps
Flatulence
Diarrhoea
Vomiting 
Rumbling stomach
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11
Q

How does the absorption of monosaccharides occur by active transport?

A

Active transport by sodium-dependent glucose transporter 1 (SGLT1) into intestinal epithelial cells and then, via GLUT2, into blood supply

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12
Q

Apart from active transport, in which other way can monosaccharides be absorbed?

A

Uptake into cells from blood via facilitated diffusion using transport proteins (GLUT1-GLUT5)

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13
Q

Where is GLUT2 found?

A

Kidney
Liver
Pancreatic beta cells
Small intestine

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14
Q

Where is GLUT4 found?

A

Adipose tissue

Striated muscle

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15
Q

Which cells have an absolute requirement for glucose? (4)

A

1) RBCs
2) Neutrophils
3) Innermost cells of kidney medulla
4) Lens of eye

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16
Q

Why do RBCs have an absolute requirement for glucose?

A

No mitochondria so can only carry out glycolysis

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17
Q

Why do the innermost cells of the kidney medulla have an absolute requirement for glucose?

A

Kidney cortex has a very high oxygen demand so the innermost cells need glucose

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18
Q

Why do the lens of the eye have an absolute requirement for glucose?

A

They have a poor oxygen supply (absorb directly from the atmosphere) so rely on glycolysis

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19
Q

True or false: CNS can use ketone bodies for some energy requirements but it prefers glucose as a fuel

A

TRUE

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20
Q

What are the functions of glycolysis? (4)

A

1) oxidation of glucose
2) NADH production (2 per glucose)
3) synthesis of ATP from ADP
4) produces C6 and C3 intermediates

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21
Q

What is the net ATP production per glucose?

A

2 ATP

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22
Q

True or false: glycolysis only occurs in selected tissues

A

FALSE - occurs in all tissues

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23
Q

True or false: there is no loss of CO2 in glycolysis

A

TRUE

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24
Q

True or false: glycolysis is the only pathway that can operate anaerobically

A

TRUE - but with additional enzyme (pyruvate dehydrogenase=PDH)

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25
Q

What is the difference between hexokinase and glucokinase?

A

Hexokinase has a lower affinity for glucose and is inhibited by glucose-6-P whereas glucokinase isn’t inhibited by glucose-6-P

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26
Q

Where is glucokinase found?

A

Liver

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27
Q

Which are the three key enzymes of glycolysis that we need to know?

A

1) Hexokinase (glucokinase)
2) Phosphofructokinase-1
3) Pyruvate kinase

28
Q

Why are there so many (10) enzymes/steps in glycolysis? (4)

A

1) chemistry easier in small steps
2) efficient energy conservation
3) gives versatility
4) allows for fine control

29
Q

What is phase 1 of glycolysis called?

A

Investment

30
Q

What is phase 2 of glycolysis called?

31
Q

What does the phosphorylation of glucose to G-6-P do?

A

Makes glucose negatively charged

Prevents passage back across plasma membrane

32
Q

How many moles of ATP are used per mole glucose in phase 1 of glycolysis?

33
Q

What happens in reaction 1 of glycolysis?

A

Glucose to glucose-6-P

34
Q

What happens in reaction 2 of glycolysis?

A

Glucose-6-P to fructose-6-P and vice versa

35
Q

What happens in reaction 3 of glycolysis?

A

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

36
Q

Which glycolysis reactions have large negative delta-G and what does this mean?

A

1, 3 and 10

Means they are irreversible

37
Q

Which step of phase 1 is the committing step and why?

A

Step 3 because it commits glucose to metabolism via glycolysis

38
Q

Which reactions are in phase 2 of glycolysis?

39
Q

What happens in reaction 4 of glycolysis?

A

Cleavage of C6 into two C3 units

40
Q

What happens in reaction 6 of glycolysis?

A

Reducing power captured (NADH)

41
Q

What happens in reactions 7 and 10 of glycolysis?

A

ATP synthesis by substrate level phosphorylation

42
Q

When is the rate of glycolysis up to 200 times greater?

43
Q

What is the key regulator of glycolysis?

A

Phosphofructokinase (PFK)

44
Q

Which reaction does phosphofructokinase (PFK) catalyse?

A

Fructose-6-P to fructose-1,6-bisphosphate

45
Q

In which two ways can phosphofructokinase be regulated?

A

1) allosteric regulation (muscle)

2) hormonal regulation (liver)

46
Q

What inhibits allosteric regulation of PFK?

47
Q

What stimulates allosteric regulation of PFK?

48
Q

What stimulates hormonal regulation of PFK?

49
Q

What inhibits hormonal regulation of PFK?

50
Q

What is BPG?

A

2,3-bisphosphoglycerate

51
Q

Where is BPG produced?

52
Q

What does BPG regulate?

A

Haemoglobin’s affinity for O2

53
Q

Why is glycerol phosphate important?

A

Important to triglyceride and phospholipid biosyntesis

54
Q

Where is glycerol phosphate produced?

A

Adipose and liver

55
Q

Why does NAD+ need to be regenerated?

A

So glycolysis can continue

56
Q

By which other method can NAD+ be regenerated?

A

Lactate dehydrogenase (LDH)

57
Q

What is the reaction that lactate dehydrogenase catalyses?

A

NADH + H+ + pyruvate NAD+ + lactate

58
Q

How is plasma lactate concentration determined?

A

Relative rates of:

1) production
2) utilisation (heart, liver, muscle)
3) disposal (kidney)

59
Q

What is the range of hyperlactaemia and what does this mean?

A

2-5mM, below renal threshold so no change in blood pH

60
Q

What is the range of lactic acidosis and what does this mean?

A

Above 5mM, above renal threshold, blood pH lowered and kidneys can no longer excrete it

61
Q

A deficiency in which three enzymes can cause galactosaemia?

A

Galactokinase
Uridyl transferase
UDP-galactose epimerase

62
Q

Which enzyme is missing in fructose intolerance and what does this mean clinically?

A

Aldolase

Fructose-1-P accumulates in liver, leading to liver damage

63
Q

What does glutathione prevent?

A

Oxidative damage to the cell

64
Q

Where does the pentose phosphate pathway start?

A

Glucose-6-phosphate

65
Q

What is NADPH from the pentose phosphate pathway needed for? (3)

A

1) reducing power for biosynthesis
2) maintenance of GSH levels
3) detoxification reactions

66
Q

The pentose phosphate pathway produces a C5-sugar, ribose. What is this required for? (2)

A

Synthesis of:

1) nucleotides
2) DNA and RNA

67
Q

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

A

Glucose 6-phosphate dehydrogenase

Semester 2-MEH (21 decks)

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