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MEH > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

how are carbohydrates broken down

A
  1. amylase in the salvia and pancreas

2. disaccharidases break down disaccharides in the small intestine

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2
Q

what are dextrins

A

smaller subunits of carbohydrates

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3
Q

name 4 disaccahridases

A

lactase, sucrase, pancreatic amylase, isomaltase

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4
Q

what is lactose intolerance

A

when you don’t have the enzyme lactase so cant break down lactose

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5
Q

what is primary lactase deficiency

A

absence of the lactase allele. Only occurs in adults

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6
Q

why is primary lactase deficiency only seen in adults

A

as children are born with lactase to break down breast milk, but they may not carry on expressing this gene into adult life

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7
Q

what is secondary lactase deficiency

A

deficiency caused by damage to the small intestine. Occurs in both adults and children

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8
Q

true or false: secondary lactase deficiency is reversible

A

true

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9
Q

what is congenital lactase deficiency

A

an extremely rare recessive defect in the lactase gene.

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10
Q

what are the symptoms of lactose intolerance

A

bloating, flatulence, diarrhoea, vomiting, rumbling stomach

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11
Q

how are monosaccharides absorbed into the intestinal epithelia cells

A

active transport by sodium dependant glucose transporter 1 (SGLT1)

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12
Q

which transporter do monosaccharides go through to enter the blood

A

GLUT2

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13
Q

how do monosaccharides enter cells from the blood

A

facilitated diffusion using GLUT1-GLUT5 transport proteins

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14
Q

where are GLUT 2 proteins found

A

kidney, liver, pancreatic beta cells, small intestine

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15
Q

where are GLUT 4 proteins found

A

adipose tissue, striated muscle

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16
Q

which cells have an absolute requirement of glucose (4)

A
  1. RBC- no mitochondria so can only get energy from glycolysis no other sources
  2. Neutrophils- use their mitochondria to produce free radicals so cant be used in energy production
  3. Kidney Medulla - cortex require lots of oxygen so little reaches medulla
  4. lens of the eye - no capillaries so no oxidative phosphorylation so relies on glycolysis
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17
Q

what does the uptake of glucose depend on

A

blood glucose concentration

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18
Q

what is stage 2 of energy release from carbohydrates

A

glycolysis

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19
Q

what occurs in phase 1 of glycolysis

A

2 ATP are used (investment)

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20
Q

why is phase 2 of glycolysis called the payback phase

A

4 ATP are produced

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21
Q

what is the net production of glycolysis from 1 molecule of glucose

A

2 NADH, 4 ATP, 2 Pyruvate

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22
Q

true or false: glycolysis is exergonic

A

true

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23
Q

what does hexokinase catalyse

A

conversion of glucose to glucose-6-Phosphate using energy from ATP. This makes the glucose negatively charged so prevents it passing out of membrane and makes the glucose more energetically favourable

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24
Q

what does phosphofructokinase catalyse

A

conversion of Fructose-6-P to Fructose-1,6-biphosphate using energy from ATP

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25
Q

what does pyruvate kinase catalyse

A

production of Pyruvate from Phosphoenolpyruvate which produces ATP

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26
Q

why are there so many steps and enzymes in glycolysis

A

allows parts to be reversed, allows for control, produces useful intermediates

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27
Q

how does glycolysis differ in the liver

A

it is driven by the supply of glucose rather than the need for energy. The liver also uses glucokinase which isn’t inhibited by its products unlike hexokinase

28
Q

true or false: glucokinase has a higher affinity for glucose than hexokinase

A

false

29
Q

why are the 2 ATP using reactions in glycolysis irreversible

A

very negative delta G values

30
Q

how is the reducing power captured in glycolysis

A

NAD+ accepts a hydrogen to become NADH

31
Q

how many reversible steps are there in glycolysis

A

3

32
Q

true or false: the rate of glycolysis is slower in cancer cells

A

false

33
Q

How is Phosphofructokinase regulated

A
  1. Allosterically inhibited by ATP and stimulated by AMP

2. Hormonally inhibited by glucagon and stimulated by insulin

34
Q

what is hexokinase inhibited by

A

its product (Glucose-6-Phosphate)

35
Q

what does high NADH or low NAD+ do to glycolysis

A

inhibits it as these are high energy signals

36
Q

what is the effect of insulin on pyruvate kinase

A

increase in insulin increases the activity of the enzyme and so increase the rate of glycolysis

37
Q

how can fats be produced from glycolysis

A

Fructose-1,6-BP splits to produce Dihydroxyacetone-P. this is then converted into glycerol phosphate in a reduction reaction using NADP. this then combines with fatty acids to produce fat

38
Q

what enzyme catalyses the conversion of dihydroxyacetone to glycerol phosphate

A

glyercol-3-phosphate dehydrogenase

39
Q

what enzyme catalyses the reaction of 1,3-bisphosglycerate into 2,3-bisphophoglycerate

A

Bisphosphoglycerate mutase

40
Q

what does 2,3-Bisphosphoglycerate do

A

lowers haemoglobin affinity for oxygen in RBC

41
Q

how many molecules of NADH are produced in glycolysis

A

2

42
Q

what does Lactate dehydrogenate catalyse

A

the conversion of pyruvate to lactate and the reverse

NADH + H+ + pyruvate NAD+ + lactate

43
Q

when are reaction catalysed by lactate dehydrogenase required

A

when you need to regenerate NAD+

low oxygen conditions

44
Q

where is lactate converted back into pyruvate

A

in the heart, kidneys and liver

45
Q

what vitamin deficiency impairs the conversion of lactate to pyruvate in the liver

A

thiamine

46
Q

what plasma lactate concentration is classed as lactic acidosis

A

above 5mM

47
Q

what is the normal lactic plasma concentration

A

below 1 mM

48
Q

what happens in lactic acidosis

A

blood pH is lowered

49
Q

what enzyme catalyses the conversion of Galactose to Galactose-1P

A

Galactokinase

50
Q

what enzyme catalyses the conversion of Galactose-1P into Glucose-1P

A

Uridyl Transferase

51
Q

what enzyme catalyses the conversion of Galactose-1P to UDP-Galactose

A

UDP-galactose epimerase

52
Q

what does deficiencies in any of the enzymes Galactokinase, Uridyl Transferase, UDP-galactose epimerase

A

Galactosaemia

53
Q

what enzyme catalyses the conversion of fructose to Fructose-1P

A

fructokinase

54
Q

what is the result of a deficiency in fructokinase

A

essential fructosuria. This is the incomplete metabolism of fructose, leading to its excretion in the urine with no clinical symptoms

55
Q

what is missing in fructose intolerance

A

the enzyme aldolase

56
Q

what does fructose intolerance result in

A

accumulation of fructose-1-P in the liver leading to liver damage. therefore, remove fructose from the diet

57
Q

what does the enzyme aldolase catalyse

A

splitting of Fructose-1P into Glyceraldehyde and DHAP

58
Q

what does Triose Kinase catalyse

A

conversion of Glyceraldehyde into glyceraldehyde-3-P

59
Q

what does TPI catalyse

A

conversion of DHAP into glyceraldehyde-3-P

60
Q

what does the pentose phosphate pathway start with

A

glucose-6-phopshate

61
Q

what catalyses the conversion of Glucose-6P into 6-Phosphogluconolactone

A

Glucose 6-Phophate dehydrogenase

62
Q

what else is produced during the conversion of Glucose-6P into 6-Phosphogluconolactone

A

NADPH

63
Q

what does the pentose phosphate pathway produce

A

Ribose 5-Phosphate (5 carbon sugar)

64
Q

what is Ribose 5-Phosphate required for

A

synthesis of nucleotides, DNA and RNA

65
Q

true of false: ATP is produced in the pentose phosphate pathway

A

false but CO2 is produced

MEH (22 decks)

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