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MCG Exam 3 > Glycolysis: Functions, pathways, energetics, regulation- Lecture 61 > Flashcards

Glycolysis: Functions, pathways, energetics, regulation- Lecture 61 Flashcards

1
Q

What is the overall reaction of glycolysis?

A

C6H12O6 + 2NAD+ + 2 Pi –> 2 CH3COCOOH (pyruvate) + 2 ATP + 2 NADH

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2
Q

Gycolysis is the only source of energy for ________ and a major source of energy for _________.

A

RBCs and normally for the brain

Embryonic tissue, retina, adrenals, some immune cells, exercising muscles

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3
Q

What is the first step of glycolysis?

A

Glucose + ATP –> Glucose-6-Phosphate + ADP + Pi

via hexokinase

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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 in glycolysis?

A

F6P + ATP –> F1,6bisP + ADP
via phosphofructokinase
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 by AMP, 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 stimulates
glucagon inhibits

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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 fifth step of glycolysis?

A

DHAP < —- > G3P
via tripse phosphate isomerase
*note that after this you have two G3P products which can continue (so everything after this step should be doubled)

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12
Q

What is the sixth step of glycolysis?

A

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

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13
Q

_____ is a high energy compound that “traps” energy that would have otherwise been ______.

A

1,3 bis PGA

released as heat

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14
Q

What is the seventh step of glycolysis?

A

1,3 bis PGA + ADP < —- > 3 PGA + ATP

via phosphoglycerate kinase

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15
Q

What is substrate level phosphorylation?

A

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

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16
Q

_____ is highly sensitive to poisoning by heavy metals such as _____.

A 
Phosphoglycerate kinase (enzyme of glycolysis 7)
Hg, Cd, Pb
17
Q

What effect does arsenic have on the body?

A

competes with Pi for G3P in the G3PDH reaction to form arseno-3-phophoglyceric 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 in RBCs who use this as their only source for ATP –> anemia

18
Q

RBCs have a mutase which converts small amounts of ______ into ________, an important allosteric effector of hemoglobin that regulates _____.

A

1,3 bis P
2,3 bis P
oxygen affinity

19
Q

What is the eighth step of glycolysis?

A

3 phosphoglycerate < —- > 2-phosphoglycerate

via phosphoglyceromutase

20
Q

What is the ninth step of glycolysis?

A

2PGA < —- > Phosphoenolpyruvate (PEP)+ H2O

via enolase

21
Q

Enolase is inhibited by ______.

A

fluoride

22
Q

What is the tenth step of glycolysis?

A

PEP + ADP –> Pyruvate + ATP

via pyruvate kinase

23
Q

Which steps of glycolysis participate in substrate level phosphorylation?

A

seven and ten

24
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

25
Q

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

A

net 2 ATP

2 ATP consumed, 4 ATP produced

26
Q

Describe fructose metabolism in the liver.

A
  1. Fructose + ATP –> Fructose 1P
    via fructokinase
  2. Fructose 1P –> Glyceraldehyde + Dihydroxyacetone P
    via aldolase
  3. Glyceraldehyde + ATP –> Glyceraldehyde 3P + ADP
    via triose kinase
  4. G3P –>–> Pyruvate
27
Q

What is hereditary fructose intolerance?

A

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

28
Q

Describe the pathway of galactose metabolism.

A
  1. Galactose + ATP –> Galactose 1P + ADP
    via galactokinase
  2. Galactose 1P + UDP-glucose –> Glucose 1P + UDP-galactose
    via galactose 1P uridylyltransferase
  3. glucose 1P –> glucose 6P
    via phosphoglucomutase
  4. Glycolysis (other tissues) or return to glucose (liver)
29
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 of galactokinase

MCG Exam 3 (21 decks)

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