Chapter 12: Glycolysis and Pyruvate Dehydrogenase (continued) Flashcards

1
Q

What are the 2 places where galactose is metabolized?

A

in brain and liver mainly

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2
Q

What are the 2 most important enzymes to remember in galactose metabolism and lead to galactosemia with deficiency of these enzymes?

A

galactokinase and galactose 1-phosphate uridyltransferase

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3
Q

How is cataracts caused in those with galactosemia?

A

result when there is conversion of excess galactose in peripheral blood to galactitol in the lens of they eye, which has aldose reductase

accumulation of galactitiol in the lens causes osmotic damage and cataracts

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4
Q

Hallmark sign of galactosemia?

A

cataracts

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5
Q

MOA for why diabetics also get cataracts?

A

same mechanism as that in galactosemia,

because aldose reductase also converts glucose to sorbitol which causes osmotic damage

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6
Q

Why is deficiency of galactose 1- phosphate uridyltransferase more severe than galactokinase deficiency?

A

because galactose 1-P accumulates in the liver, brain, and other tissues

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7
Q

Inheritance pattern of galactosemia?

A

AR

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8
Q

What is primary lactose intolerance caused by?

A

hereditary deficiency of lactase

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9
Q

What is secondary lactase deficiency caused by?

A

any age by GI disturbances such as celiac sprue, colitis, or viral-induced damage to intestinal mucosa

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10
Q

What are the symptoms of lactase deficiency caused by?

A

attributed to bacterial fermentation of lactose to a mixture of CH4, H2, and small organic acids. The acids are osmotically acitve and result in the movement of water into the intesitinal lumen

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11
Q

How do you diagnose lactose intolerance?

A

positive H breath test after an oral lactose load

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12
Q

How do you treat lactose intolerance?

A

dietary restriction of milk and milk products (except unpasteruized yogurt, which contains active lactobacillus or by lactase pills

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13
Q

How do you diagnose galactosemia?

A

newborn screening heel prick test

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14
Q

What is the treatment for newborns diagnosed with galactosemia in the first few weeks of life?

A

formulas containing galactose free carbs are given

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15
Q

Draw out metabolism of fructose.

A

Draw out diagram

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16
Q

Fructokinase deficiency symptoms? How is one usually diagnosed?

A

some dehydration and dumping of sugar in urine but otherwise benign

usually detected incidentally when urine is checked for glucose with a dipstick

17
Q

Aldolase B def symptoms?

A
  • lethargy, vomiting
  • liver damage, hyperbilirubinemia
  • hypoglycemia
  • hyperuricemia, lactic acidosis
  • renal proximal tubule defect (Fanconi)
18
Q

Another name for aldolase B deficiency?

A

fructose 1-P aldolase activity deficiency

19
Q

What is the biochemical reason why a high-fructose drink supplies a quick source of energy in both aerobic and anaerobic cells?

A

because DHAP and glyceraldehyde are downstream from the key regulatory and rate limiting enzyme PFK-1

20
Q

What is fructose found in?

A

honey and fruit

21
Q

What are important enzymes to remember in the metabolism of fructose?

A

fructokinase and fructose 1-P aldolase (aldolase B)

22
Q

Where are the 2 places fructose is commonly metabolized?

A

in the liver and renal proximal tubules

23
Q

Why does fructose accumulation in the body not cause cataracts?

A

because it is not an aldose sugar. and therefore not a substrate for aldose reductase in the lens

24
Q

Inheritance pattern for hereditary fructose intolerance?

A

AR

25
Q

PDH in the liver is activated by insulin, does this hold true for PDH in the brain and nerves?

A

no; the enzyme (actually, a complex of 5 enzymatic activities) is not responsive to hormones in these locations

26
Q

What are the cofactors and coenzymes used by PDH?

A

Tender Love and Care for Nancy

  • thiamine pyrophosphate (TPP) from the vitamin thiamine
  • Lipoic acid
  • Coenzyme A (CoA) from pantothenate
  • FAD (H2) from riboflavin
  • NAD (H) from niacin (some may be synthesized from tryptophan)
27
Q

What product of metabolism is PDH inhibited by?

A

acetyl-CoA

28
Q

Draw out the path for glycolysis focusing on PDH and products.

A

Draw out diagram

29
Q

Compare and contrast Wernicke and Korsakoff?

A

Wernicke = peripheral neuropathy
Korsakoff = psychosis

30
Q

Wet beri beri major symptom?

A

congestive heart failure

31
Q

Why is CHF caused in wet beri-beri?

A

owing to inadequate ATP and accumulation of ketoacids in the cardiac muscle

32
Q

What are other enzymes (complexes?) besides PDH that utilize thiamine?

A
  • a-ketoglutarate dehydrogenase (citric acid cycle)
  • Branched chain ketoacid dehydrogenase (metabolism of branched-chain amino acids)
  • transketolase
33
Q

What is the treatment if thiamine deficiency is suspected in an individual?

A

give IV thiamine prior to glucose (dextrose) admin (to prevent lactic acidosis)

34
Q

Thiamine deficiency significantly impairs oxidation of what?

A

glucose oxidation

35
Q

How does thiamine deficiency and the enzymes that require thiamine affect brain, cardiac muscle and muscle?

A

it impairs glucose oxidation so highly aerobic tissues like brain and cardiac muscle fail first.

in addition, branched chain amino acids are sources of energy in brain and muscle