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MCG Review > AC Lecture 61: Glycolysis: Functions, pathways, energetics, regulations > Flashcards

AC Lecture 61: Glycolysis: Functions, pathways, energetics, regulations Flashcards

1
Q

What is the basic overall reaction of glycolysis?

A

Glucose + 2 NAD+ + 2Pi + ADP –> 2 pyruvic acid + 2ATP + 2NADH

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2
Q

What is the first step of Glycolysis?

A

Glucose + ATP –> Glucose-6-P + ADP +Pi via hexokinase

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3
Q

What organ systems use glycolysis for energy exclusively?

A

RBCs and brain

embryonic tissue, retina, adrenals, some immune cells, exercising muscles (major source)

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4
Q

Which steps in glycolysis are irreversible?

A

1, 3, and 10

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5
Q

What is the second step of glycolysis?

A

G6P –> Fructose 6-P

via phosphoglucoisomerase

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6
Q

What is the third step of glycolysis?

A

F6P + ATP –> F1,6bisP + ADP

via PF1K RATE LIMITING

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7
Q

What regulates the rate limiting step of glycolysis (not in the liver)?

A

the third step of glycolysis is catalyzed by PFK which is…
inhibited by ATP and citrate
stimulated byAMP, Pi, NH4, F1,6bisP

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8
Q

What kinds of sites does PFK have?

A

two substrate binding sites (ATP, F6P)
two allosteric inhibitory sites
four allosteric activator sites

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9
Q

What regulates the rate limiting step of glycolysis (in the liver)?

A

the third step of glycolysis is catalyzed by PFK which is…
insulin stimulated
glucagon inhibited

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10
Q

What is the fourth step of glycolysis?

A

F1,6bisP –> DHAP + G3P

via aldolase

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11
Q

What is the sixth step of glycolysis?

A

G3P + NAD+ + Pi –> 1,3bis phosphoglyceric acid + NADH
via gluceraldehyde 3-P dehydrogenase
Note: oxygen independent

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12
Q

What is the function of 1,3 bis PGA?

A

it is a high energy compound that traps energy that would have been released as heat

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13
Q

What is the seventh step of glycolysis?

A

1,3 bis PGA + ADP –> 3 PGA + ATP

via phosphoglycerate kinase

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14
Q

What is substrate level phosphorylation?

A

the transfer of energy to a high energy intermediate which can produce ATP

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15
Q

Which enzyme in glycolysis is highly sensitive to poisoning by heavy metals?

A 
phosphogycerate kinase (enzyme of glycolysis 7)
Hg, Cd, Pb
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16
Q

What effect does arsenic have on the body?

A

competes with Pi for G3P in the G3PDH reaction to form arseno-3-phosphoglyceric acid rather than 1,3 bisP that releases energy as heat rather than as ATP
glycolysis continues, but no ATP is produced- this is a problem for RBCs who use this as their only source for ATP –> anemia

17
Q

What is the eighth step of glycolysis?

A

3 phosphoglycerate –> 2-phosphoglycerate

via phosphoglyceromutase

18
Q

What is the ninth step of glycolysis?

A

2PGA –> Phosphoenolpyruvate (PEP) + H2O

via enolase

19
Q

What is an inhibitor of enolase?

A

fluoride

20
Q

What is the tenth step of glycolysis?

A

PEP + ADP –> Pyruvate + ATP

via pyruvate kinase

21
Q

Which steps of glycolysis participate in substrate level phosphorylation?

A

seven and ten

22
Q

How is pyruvate kinase regulated?

A 
inhibited by ATP, NADH, and acetyl CoA
stimulated by F1,6 bis P
inhibited by glucagon (epi)
cAMP-PKA
phosphorylation
stimulated by insulin
23
Q

What is the net ATP yield for one mol of glucose through glycolysis?

A

net 2 ATP

2 ATP consumed, 4 ATP produced

24
Q

Describe the process of fructose metabolism in the liver.

A
  1. Fructose + ATP –> Fructose 1P
    via fructokinase
  2. Fructose 1P –> Glyceraldehyde + Dihydroxyacetone P
    via aldose
  3. Glyceraldehyde + ATP –> Glyceraldehyde 3P + ADP
    via triose kinase
  4. G3P –>–> Pyruvate
25
Q

What is hereditary fructose intolerance?

A

Aldose B in liver is replaced by aldolase A which cannot react with Fructose 1P

26
Q

Describe the pathway of galactose metabolism.

A
  1. Galactose + ATP –> Galactose 1P + ATP
    via galactokinase
  2. Galactose 1P + UDP-glucose –> Glucose 1P + UDP-galactose
    via galactose 1P uridylyltransferase
  3. glucose 1P –> glucose 6P
    via phosphoglucomutase
27
Q

What is galactosemia?

A

mainly deficiency of galactose 1P resulting in accumulation or toxic galactose 1P uridylytransferase in liver, may also be caused by deficiency in galactokinase

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