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Metabolism > Review 1: Glycolysis > Flashcards

Review 1: Glycolysis Flashcards

1
Q

What energy source does the skeletal muscle use at rest? exertion?

A

fatty acids

gluocse

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2
Q

What energy source does the heart use?

A

fatty acids

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3
Q

What is the energy source for the brain during starvation?

A

ketone bodies

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4
Q

How many grams of glucose does the brain need per day?

A

120

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5
Q

How many grams of glucose does skeletal muscle need per day?

A

40

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6
Q

What is the normal min of fasting blood glucose?

A

60mg/dL

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7
Q

What enzyme(s) convert glucose to glucose 6-phosphate?

A

hexokinase/glucokinase

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8
Q

What enzyme converts fructose 6-phosphate to fructose 1,6-bisphosphate?

A

PFK1 (phosphofructokinase)

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9
Q

When is NAD+ required in glycolysis?

A

During the conversion of glyceraldehyde 3-phosphate to bisphosphate (missing this and glycolysis stalls at priming stagE and goes towards lactate acid production)

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10
Q

What enzyme converts PEP (phosphoenolpyruvate) to pyruvate?

A

pyruvate kinase

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11
Q

What enzyme converts pyruvate into oxaloacetate?

A

pyruvate carboxylase

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12
Q

Where is glucokinase found?

A

liver and pancreas

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13
Q

Between hexokinase and glucokinase, which has greater glucose affinity?

A

hexokinase (lower Km)

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14
Q

Which enzyme is insulin inducible, hexokinase or glucokinase?

A

glucokinase

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15
Q

What inhibits hexokinase?

A

its product, glucose 6-phosphate

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16
Q

What inhibits glucokinase?

A

location - inhibited in the nucleus, active in the cytosol

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17
Q

What are possible fates of pyruvate?

A

1) Alanine (transamination)
2) Oxaloacetate (pyruvate carboxylase)
3) Lactate (lactate dehydrogenase)
4) TCA cycle (pyruvate dehydrogenase)

18
Q

What are the clinical signs of PDH deficiency?

A

increases in circulatory pyruvate and lactate

microcephaly, poor muscle coordination

19
Q

What are the clinical signs of pyruvate carboxylase deficiency?

A

increases in blood alanine, lactate, pyruvate

developmental delay, seizures, metabolic acidosis

20
Q

What must be regenerated to maintain glycolytic flux?

A

NAD+

21
Q

What reaction in glycolysis uses NAD+?

A

glyceraldehyde 3-P dehydrogenase reaction

22
Q

How does anaerobic respiration replenish the NAD+?

A

through a reduction reaction leading to lactate or ethanol production

23
Q

How does aerobic respiration replace NAD+?

A

metabolite shuttle system

24
Q

True or false: NADH can cross the mitochondrial membrane

A

FALSE (it cannot)

25
Q

Name 3 ways NAD+ can be regenerated:

A

1) Lactate dehydrogenase
2) Malate-aspartate shuttle
3) Glycerol-phosphate shuttle

26
Q

Which enzyme is a multienzmye complex (E1, E2, E3) that catalyzes the conversion of pyruvate and coenzyme A to acetyl CoA?

A

Pyruvate dehydrogenase (PDH)

27
Q

What vitamins are required for PDH function?

A

B1, B2, B3, and B5

28
Q

What limitations do patients with Lactate Dehydrogenase A Deficiency face?

A

exercise (inability to utilize glycolysis to produce ATP needed for muscle contraction under anaerobic conditions)

29
Q

What intermediate specifically suffers with lactate dehydrogenase A deficiency?

A

the level of NAD+ (becomes limiting during exercise so flux thru glyceraldehyde 3-P dehydrogenase reaction is inhibited)

30
Q

What is the net ATP gain in glycolysis?

A

2 ATP

31
Q

How many ATP are consumed during glycolysis?

A

2 (but 4 are produced - 2 per pyruvate)

32
Q

Low levels of cellular NADH favor ___________ (aerobic/anaerobic respiration)

A

aerobic (decrease lactate formation)

33
Q

Oxygen is required for reoxidation of NADH in the mitochondria or cytosol?

A

BOTH

34
Q

During galactosemia, what two things build up?

A

galactitol and galactose 1-phosphate

35
Q

What causes galactosemia?

A

deficiency of

1) galactose 1-phosphate uridyltransferase (classic and most severe)
2) galactokinase

36
Q

What step converts galactose to galactitol?

A

oxidation of NADPH to NADP+

37
Q

What enzyme converts galactose to galactose 1-P?

A

galactokinase

38
Q

What enzyme converts galactose 1-P to glucose 1-P?

A

gal-1-P uridyltransferase

39
Q

What are some clinical features of galactosemia?

A

cataracts

40
Q

What is aldolase B and why is it important?

A

Fructose-bisphosphate aldolase B

plays a role in glycolysis and gluconeogenesis

deficiency in this enzyme leads to fructose intolerance

41
Q

Deficiency of ___________ __ leads to fructose intolerance

A

aldolase B

42
Q

What does fructose accumulation lead to?

A

high uric acid and high lactic acid

Metabolism (11 decks)

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