Flashcards in Biochem metabolism Deck (129)
How does fructose bypass rate limiting step in glycolysis (PFK)?
aldolase B enzyme to yield glyceraldehyde & dihydroxyacetone-P
What type of sugar is galactose?
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
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
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
What is the most serious defects in classic galactosemia?
What enzyme other than G6P can trap glucose in the cell? how?
aldose reductase converts glucose to sorbitol (alcohol relative)
Once sorbitol is trapped within the cell, what occurs so it can be used for energy metabolism?
sorbitol DH converts it to fructose
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
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
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
What tissues have ONLY aldose reductase?
Schwann cells, retina, lens, kidneys
What type of sugar is lactose? what makes it?
disacaridase made of glucose & galactose
What are the causes of lactase deficiency?
Age dependent loss in enzyme;
hereditary lactose intolerance (AA, asians);
gastroenteritis due to temporary loss of microvilli
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
Where is lactate used?
energy molecule that goes to liver cytoplasm for glucose to go to skeletal muscle via the Cori cycle
Give the essential amino acids and what they produce
glucogenic=> Met, Val, His
Gluco/Keto-genic => Ile, Phe, Thr, Trp
Ketogenic => leu, Lysine
What amino acid is targeted by oral HSV?
What are the acidic amino acids?
Aspartate & glutamate => negative at body pH
What are the basic amino acids? which has no charge at body pH
Arginine, Lysine, Histidine
His has no charge at body pH
Which amino acids are required during periods of growth?
arginine & histidine
Which amino acids are increased in histones? why?
Arginine & lysine so the negative charge DNA can bind
What is the rate limiting enzyme of urea cycle? where is it located?
CPS 1 located in mitochondria
Other than CPS 1, what other enzyme is found in the mitochondria?
ornithine transcarbamoylase in the conversion of ornithine to citrulline
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
What molecule is essential for communicating anaerobic metabolism?
Amino transferases (ALT, AST) require what?
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
Sx of ammonia intoxication?
tremor (asterixis), slurred speech, somnolence, vomit, cerebral edema, blurring of vision