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EOM Test 4 > Glucose and Fructose Metabolism > Flashcards

Glucose and Fructose Metabolism Flashcards

1
Q

Why is glucose used as fuel?

A

Yields a good amount of energy

Efficiently stored in polymeric form

Some tissues meet their energy needs on glucose only

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2
Q

What three organs/cells use glucose a sole energy source?

A

Brain

Red blood cells

Sperm

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3
Q

One molecule of glucose in the glycolytic pathway produces…?

A

2 ATP

2 NADH

2 Pyruvate

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4
Q

How is glucose transported into the cell?

A

Facilitate transport mediated by 5 glucose transporters

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5
Q

What is the role of insulin?

A

Increases number and activity of glucose transporters

GLUT1-5

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6
Q

Insulin is not required for glucose transport into what organ?

A

Liver

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7
Q

What is the function of hexokinase?

A

First step of glycolysis, Phosphorylates glucose

Present in most tissues

Inhibited by Glucose-6-phosphate

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8
Q

What is glucokinase?

A

Enzyme that catalyzes first reaction of glycolysis

Present only in the liver, and is only active after a meal

Not inhibited by G6P (unlike hexokinase)

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9
Q

What is the function of phosphofructokinase-1?

A

Catalyzes third glycolytic reaction, Fructose-6-phosphate –> Fructose 1,6-bisphosphate

Regulated step

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10
Q

What things increase the activity of PFK-1?

A

AMP

ADP

Fructose-2,6-bisphosphate

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11
Q

What decreases the activity of PFK-1?

A

ATP

Citrate

H+

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12
Q

What is the function of pyruvate kinase?

A

Catalyzes the last reaction of glycolysis

Phosphoenolpyruvate –> Pyruvate

Key regulatory enzyme for glycolysis

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13
Q

What activates and inhibits pyruvate kinase?

A

Activators: F-1,6BP, Dephosphorylation

Inhibitors: ATP, phosphorylation, alanine

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14
Q

What is the Warburg effect?

A

Cancer cells carry out glycolysis at much higher rate than normal cells, even when oxygen is available

Principle behind PET scans

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15
Q

What are the fates of pyruvate under anaerobic conditions?

A

Ethanol - fermentation (plants)

Lactic Acid - humans

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16
Q

What is the fate of pyruvate under aerobic conditions?

A

Acetyl CoA in mitochondria

17
Q

How is galactose produced and what is it metabolized to?

A

Product of lactose digestion

Metabolized to glucose-1-phosphate

18
Q

What is the cause of galactosemia?

A

Defect in galactose-1-phosphate uridyltransferase

19
Q

What problems are associated with galactosemia?

A

Galactose-1-Phosphate build up, toxic to liver

Galactitol build up, cataracts and CNS damage

20
Q

How is galactosemia treated?

A

Removal of lactose and galactose from diet

21
Q

Describe fructose metabolism.

A

More rapidly metabolized than glucose

Phosphorylated than cleaved to DHP and glyceraldehyde by aldolase B

22
Q

What causes the accumulation of F-1-P in fructose metabolism?

A

The activity of fructokinase exceeds aldolase B.

More F1P is produced than can be broken down

23
Q

What does accumulation of F-1-P cause?

A

Inhibits ox-phos in the liver and causes damage

24
Q

Inhibiting ox-phos in the liver due to fructose metabolism causes build up of ADP and AMP, what will this result in?

A

Catabolism of ADP and AMP will result in high concentrations of uric acid which can cause gout

25
Q

How does fructose metabolism affect PFK-1?

A

Bypasses the enzyme, which controls glycolysis

Leads to high levels of lactic acid and lipogenesis

26
Q

What does Aldolase B deficiency cause?

A

Fructose intolerance

27
Q

What does fructokinase deficiency cause?

A

Essential fructosuria

28
Q

What reactions in glycolysis use ATP?

A

Hexokinase

Phosphofructokinase-1

29
Q

What reactions in glycolysis produce ATP?

A

Phosphoglycerate kinase

Pyruvate kinase

30
Q

What reaction in glycolysis produces NADH?

A

Glyceraldehyde-3-phosphate dehydrogenase

EOM Test 4 (19 decks)

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