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Basic Biochemistry > 44. Glycolysis > Flashcards

44. Glycolysis Flashcards

1
Q

major pathway for glucose metabolism that converts glucose into 3 carbon compounds to provide energy

A

glycolysis

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2
Q

where does glycolysis occur

A

cytosol of all mammalian cells

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3
Q

what is the substrate of glycolysis?

A

glucose

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4
Q

what are end products of glycolysis

A

2 molecules of either pyruvate or lactate

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5
Q

rate limiting step of glycolysis

A

fructose-6-phosphate –> fructose-1,6- biphosphate

enz. Phosphofructokinase-1

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6
Q

important steps of glycolysis

A
  1. glucose -> glucose-6-phosphate

enz. hexokinase/ glucokinase

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7
Q

fructose-6-phosphate

phosphorylation

A

fructose-6-phosphate –> fructose-1,6-biphosphate

PFK-1

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8
Q

PFK-2 product

A

fructose-2,6- biphosphate

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9
Q

PEP -> pyruvate

A

pyruvate kinase

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10
Q

2 steps of glycolysis produce ATP via substrate level phosphorylation

A

(1) 1,3-biphosphoglycerate –> 3-phosphoglycerate
enz. phosphoglycerate kinase

(2) phosphoenolpyruvate –> pyruvate
enz. pyruvate kinase

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11
Q

production of NADH in glycolysis

A

glyceraldehyde-3-phosphate –> 1,3 biphosphoglycerate

enz.glyceraldehyde-3-phosphate dehydrogenase

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12
Q

this enzyme can phosphorylate glucose and other hexoses is present in most tissues

A

hexokinase

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13
Q

glucokinase is present in

A
  • liver parenchymal cells

* islets of pancreas

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14
Q

hexokinase is inhibited by

A

glucose-6-P

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15
Q

glucokinase is inhibited by

A

fructose-6-P

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16
Q
  • this enzyme can phosphorylate glucose and other hexoses
  • low Km,high affinity
  • low Vmax
A

hexokinase

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17
Q
  • this enzyme can phosphorylate glucose and other hexoses

* induced by insulin

A

glucokinase

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18
Q

•this enzyme can phosphorylate glucose and other hexoses

  • High km, low affinity
  • high Vmax
A

glucokinase

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19
Q

activator of PFK-1

A
  • fructose-2,6-BP

* AMP

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20
Q

activator of PFK-2

A
  • well fed state
  • ÎÎ insulin
  • dec glucagon
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21
Q

inhibitor of PFK-1

A
  • citrate

* ATP

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22
Q

inhibitor of PFK-2

A
  • fasting state
  • dec insulin
  • inc glucagon
23
Q

how many ATP is yielded per molecule of PEP

A

1 ATP

24
Q

PEP -> pyruvate
enz. pyruvate kinase

activated by?

A

fructose-1,6-BP

25
Q

PEP -> pyruvate
enz. pyruvate kinase

inhibited by?

A

glucagon

26
Q

type of glycolysis

  • cells without mitochondria
  • cells without sufficient O2
A

anaerobic glycolysis

27
Q

type of glycolysis
•cells with mitochondria
•with adequate O2 supply

A

aerobic glycolysis

28
Q

end product of anaerobic glycolysis

A

lactate

29
Q

end product of

aerobic glycolysis

A

pyruvate

30
Q

used to reduce pyruvate to lactate

A

NADH

31
Q

major fate of pyruvate in lens, cornea, eye, kidney, medulla, testes, RBCs,WBCs

A

anaerobic glycolysis

32
Q

lactic acidosis is seen in

A
  • vigorous exercise
  • septic shock
  • cancer cachexia
33
Q

NADH to pass through inner mitochondrial membrane requires

A

•glycerophosphate shuttle
or
•malate aspartate shuttle

34
Q

ATP yield with glycerophosphate shuttle

A

1 NADH = 1.5 ATPs

35
Q

ATP yield with

malate aspartate shuttle

A

1 NADH = 2.5 ATPs

36
Q

this shuttle of NADH is found in

most tissues and heart muscle

A

malate aspartate shuttle

37
Q

this shuttle of NADH is found in

brain and white muscle

A

glycerophosphate shuttle

38
Q

net ATP yield

aerobic glycolysis

A

5 or 7

39
Q

net ATP yield with anaerobic glycolysis

A

2 ATP

40
Q

thhis is found in RBCs where rxn catalyzed by phosphoglycerate kinase is bypassed

A

2,3-biphosphoglycerate

1,3- BPG –> 2,3-BPG
enz. biphosphoglycerate mutase

41
Q

Fates of Pyruvate :

A
  1. Anaerobic glycolysis
    •lactate (lactate dehydrogenase)
  2. Gluconeogenesis
    •oxaloacetate (pyruvate carboxylase)
  3. Citric acid cycle
    •acetyl coa (pyruvate dehydrogenase)
  4. Fermentation
    •Ethanol (pyruvate decarboxylase)
42
Q

pyruvate –> acetyl coa

A

pyruvate –> acetyl coa

enzyme: pyruvate dehydrogenase complex

co-enzymes:

  1. thiamine pyrophosphate
  2. FAD
  3. NAD+
  4. coenzyme A (pantothenic acid)
  5. lipoic acid
43
Q

most common enzyme defect in glycolysis

A

pyruvate kinase deficiency

44
Q

provide lipids as alternative fuel

in the muscle

A

muscle phosphofructokinase

45
Q

most common cause of congenital lactic acidosis

A

pyruvate dehydrogenase deficiency

46
Q

inheritance of pyruvate dehydrogenase deficiency

A

X-linked dominant

47
Q

clinical manifestations of pyruvate dehydrogenase deficiency

A
  • lactic acidosis

* brain : ÎÎ lactate , decrease acetyl COA -> brain deprivation of acetyl CoA -> psychomotor retardation and death

48
Q

tx pyruvate dehydrogenase deficiency

A

ketogenic diet

49
Q

aldolase A deficiency manifests as

A

hemolytic anemia

50
Q

pyruvate kinase deficiency leads to

A

hemolytic anemia

51
Q

mutations that dec activity of glucokinase leads to

A

Maturity onset diabetes of the young, type 2

52
Q

Maturity onset diabetes of the young, type 2
due to glucokinase dec activity
tx

A

majority no tx required

except during pregnancy

53
Q

arsenic poisoning competes with

A

inorganic phosphate as a substrate

for glyceraldehyde-3-P dehydrogenase

54
Q

chronic alcoholism effect on tiamine

A

inhibits absorption

cause fatal pyruvic and lactic acidosis

Basic Biochemistry (50 decks)

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