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Flashcards in Biochem metabolism Deck (129)
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61

How does fructose bypass rate limiting step in glycolysis (PFK)?

aldolase B enzyme to yield glyceraldehyde & dihydroxyacetone-P

62

What type of sugar is galactose?

monomer sugar

63

Name enzyme & inheritance of galactokinase deficiency. What are the Sx of the deficiency?

AR deficient galactokinase leads to accumulation of galactitol if galactose is in the diet but will appear in blood & urine

may present as failure to track objects or develop social smile due to infantile cataracts

64

Name enzyme & inheritance of classic galactosemia. What causes the damage?

AR absence of galactose-1-phosphate uridyltransferase that leads to accumulation of toxins such as GALACTITOL that accumulates in lens of eye

65

Sx & Tx of classic galactosemia

Sx are failure to thrive, jaundice, hepatomegaly, infantile cataracts, mental retardation
Tx must exclude galactose & lactose (galactose + glucose) from diet

66

What is the most serious defects in classic galactosemia?

PO4 depletion

67

What enzyme other than G6P can trap glucose in the cell? how?

aldose reductase converts glucose to sorbitol (alcohol relative)

68

Once sorbitol is trapped within the cell, what occurs so it can be used for energy metabolism?

sorbitol DH converts it to fructose

69

Tissues that have insufficient amount of sorbitol DH are at risk for what?

osmotic damage due to accumulation leading to cataracts, retinopathy, peripheral neuropathy as in chronic hyperglycemia of diabetics

70

A patient w/ galactokinase deficiency will use what enzyme to make its damaging toxic metabolite?

High galactose uses aldose reductase to convert to galactitol that will accumulate in the eye

71

What tissues have both aldose reductase & sorbitol DH? What enzyme would have to be deficient to cause osmotic damage?

Liver, ovaries, seminal vesicles => sorbitol DH

72

What tissues have ONLY aldose reductase?

Schwann cells, retina, lens, kidneys

73

What type of sugar is lactose? what makes it?

disacaridase made of glucose & galactose

74

What are the causes of lactase deficiency?

Age dependent loss in enzyme;
hereditary lactose intolerance (AA, asians);
gastroenteritis due to temporary loss of microvilli

75

What are the Sx & Tx for lactase deficiency?

Sx are bloating, cramps, osmotic diarrhea

Tx is to avoid dairy products or add lactase pills to diet

76

Where is lactate used?

energy molecule that goes to liver cytoplasm for glucose to go to skeletal muscle via the Cori cycle

77

Give the essential amino acids and what they produce

glucogenic=> Met, Val, His
Gluco/Keto-genic => Ile, Phe, Thr, Trp
Ketogenic => leu, Lysine

78

What amino acid is targeted by oral HSV?

lysine

79

What are the acidic amino acids?

Aspartate & glutamate => negative at body pH

80

What are the basic amino acids? which has no charge at body pH

Arginine, Lysine, Histidine

His has no charge at body pH

81

Which amino acids are required during periods of growth?

arginine & histidine

82

Which amino acids are increased in histones? why?

Arginine & lysine so the negative charge DNA can bind

83

What is the rate limiting enzyme of urea cycle? where is it located?

CPS 1 located in mitochondria

84

Other than CPS 1, what other enzyme is found in the mitochondria?

ornithine transcarbamoylase in the conversion of ornithine to citrulline

85

What is the function of the urea cycle? What amino acids are necessary to carry it out?

Amino acids break down to pyruvate, acetyl-CoA so nitrogen must be excreted to avoid excess so converted to urea

Aspartate donates NH4 while Arginine is final step before urea is made

86

What molecule is essential for communicating anaerobic metabolism?

lactate

87

Amino transferases (ALT, AST) require what?

vitamin B6

88

Hyperammonemia occurs how? what are the results?

acquired via liver dz or hereditary via urea cycle deficiencies => results in excess NH4 that depletes a-KG leading to inhibition of TCA cycle

89

Sx of ammonia intoxication?

Hepatoencephalopathy

tremor (asterixis), slurred speech, somnolence, vomit, cerebral edema, blurring of vision

90

Tx for hyperammonemia

limit protein in diet & benzoate or phenylbutyrate can be given to decrease ammonia levels;
lactulose