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
what does pyruvate kinase catalyse
production of Pyruvate from Phosphoenolpyruvate which produces ATP
26
why are there so many steps and enzymes in glycolysis
allows parts to be reversed, allows for control, produces useful intermediates
27
how does glycolysis differ in the liver
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
true or false: glucokinase has a higher affinity for glucose than hexokinase
false
29
why are the 2 ATP using reactions in glycolysis irreversible
very negative delta G values
30
how is the reducing power captured in glycolysis
NAD+ accepts a hydrogen to become NADH
31
how many reversible steps are there in glycolysis
3
32
true or false: the rate of glycolysis is slower in cancer cells
false
33
How is Phosphofructokinase regulated
1. Allosterically inhibited by ATP and stimulated by AMP | 2. Hormonally inhibited by glucagon and stimulated by insulin
34
what is hexokinase inhibited by
its product (Glucose-6-Phosphate)
35
what does high NADH or low NAD+ do to glycolysis
inhibits it as these are high energy signals
36
what is the effect of insulin on pyruvate kinase
increase in insulin increases the activity of the enzyme and so increase the rate of glycolysis
37
how can fats be produced from glycolysis
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
what enzyme catalyses the conversion of dihydroxyacetone to glycerol phosphate
glyercol-3-phosphate dehydrogenase
39
what enzyme catalyses the reaction of 1,3-bisphosglycerate into 2,3-bisphophoglycerate
Bisphosphoglycerate mutase
40
what does 2,3-Bisphosphoglycerate do
lowers haemoglobin affinity for oxygen in RBC
41
how many molecules of NADH are produced in glycolysis
2
42
what does Lactate dehydrogenate catalyse
the conversion of pyruvate to lactate and the reverse | NADH + H+ + pyruvate NAD+ + lactate
43
when are reaction catalysed by lactate dehydrogenase required
when you need to regenerate NAD+ | low oxygen conditions
44
where is lactate converted back into pyruvate
in the heart, kidneys and liver
45
what vitamin deficiency impairs the conversion of lactate to pyruvate in the liver
thiamine
46
what plasma lactate concentration is classed as lactic acidosis
above 5mM
47
what is the normal lactic plasma concentration
below 1 mM
48
what happens in lactic acidosis
blood pH is lowered
49
what enzyme catalyses the conversion of Galactose to Galactose-1P
Galactokinase
50
what enzyme catalyses the conversion of Galactose-1P into Glucose-1P
Uridyl Transferase
51
what enzyme catalyses the conversion of Galactose-1P to UDP-Galactose
UDP-galactose epimerase
52
what does deficiencies in any of the enzymes Galactokinase, Uridyl Transferase, UDP-galactose epimerase
Galactosaemia
53
what enzyme catalyses the conversion of fructose to Fructose-1P
fructokinase
54
what is the result of a deficiency in fructokinase
essential fructosuria. This is the incomplete metabolism of fructose, leading to its excretion in the urine with no clinical symptoms
55
what is missing in fructose intolerance
the enzyme aldolase
56
what does fructose intolerance result in
accumulation of fructose-1-P in the liver leading to liver damage. therefore, remove fructose from the diet
57
what does the enzyme aldolase catalyse
splitting of Fructose-1P into Glyceraldehyde and DHAP
58
what does Triose Kinase catalyse
conversion of Glyceraldehyde into glyceraldehyde-3-P
59
what does TPI catalyse
conversion of DHAP into glyceraldehyde-3-P
60
what does the pentose phosphate pathway start with
glucose-6-phopshate
61
what catalyses the conversion of Glucose-6P into 6-Phosphogluconolactone
Glucose 6-Phophate dehydrogenase
62
what else is produced during the conversion of Glucose-6P into 6-Phosphogluconolactone
NADPH
63
what does the pentose phosphate pathway produce
Ribose 5-Phosphate (5 carbon sugar)
64
what is Ribose 5-Phosphate required for
synthesis of nucleotides, DNA and RNA
65
true of false: ATP is produced in the pentose phosphate pathway
false but CO2 is produced