Protein and AA Metabolism

Question 1

Hartnup disease

Answer 1

Defective transport of nonpolar or neutral amino acids leads to concentrated levels in urine. Tryptophan is the major AA effected

Question 2

Cystinuria

Answer 2

Defective transport of dimeric cystine and Arg, lys

Formation of cystine crystals in the kidneys

Question 3

Serine can be converted to which AAs

Answer 3

Cysteine

Glycine

Question 4

Aspartate can be converted to which AAs

Answer 4

Asparagine (OAA–>Asp–>Asn)

Question 5

Pyruvate can be converted to which AAs

Answer 5

Alanine

Question 6

Glutamate can be converted to

Answer 6

Glutamine, proline, arginine (a-ketoglutarate precursor)

Question 7

What activates trypsinogen and where is it located

Answer 7

Enterokinase/enteropeptidase in intestinal mucosa first activates trypsinogen, then trypsin can activate it as well

Question 8

Ketogenic AAs include

Answer 8

Leucine, lysine

Question 9

Which AAs are both ketogenic and glucogenic

Answer 9

Ile, Trp, Phe, Tyr, Thr

FYIWT

Question 10

Aminotransferase/transaminase function

Answer 10

Catalyzes a-ketoacid + a-amino acid–> amino acid and a-ketoacid

Question 11

What is the a-ketoacid of alanine

Answer 11

Pyruvate

Question 12

What is the a-ketoacid of Aspartate

Answer 12

Oxaloacetate

Question 13

Increased alanine aminotransferase (ALT) enzymes means what

Answer 13

Increase in viral hepatitis, liver cell necrosis, prolonged circulatory collapse

Question 14

Increased Aspartate aminotransferase (AST) enzymes means what

Answer 14

Increases 6-8hrs after myocardial infarction, biliary cirrhosis, liver cancer, pancreatitis, alcoholic cirrhosis

Question 15

What is the primary cause of neurological disorders

Answer 15

Hyperammonemina

Question 16

Defects in methionine pathway (list 3 causes) can cause what

Answer 16

Vitamin B6 or B12 deficiency, mutation in CBS (cystathionine b-synthase)
Homocystinuria
Hyperhomocystinuria

Question 17

Where are branched chain amino acids degraded

Answer 17

Muscle, brain, kidney (NOT LIVER)

Question 18

Defects in branched chain amino acid pathway causes what

Answer 18

Maple syrup urine disease MSUD

Question 19

What causes phenylketonuria and what are the side effects

Answer 19

Defects in Phenylalanine hydroxylase, causing Phenyllactate and Phenylacetate to be formed, which disrupt neurotransmission and myelin formation.
Patients urine has a musty odor and impairment of melanin synthesis

Question 20

Hyper vs hypothyroidism

Answer 20

Hyper- Low TSH, High T3/T4

Hypo- High TSH, Low T4

Question 21

Thyroid hormone is a derivative of what AA

Answer 21

Tyrosine

Question 22

What is the significance of CK-MB

Answer 22

Elevated serum levels of CK-MB are seen in patients who had an MI recently

Question 23

What causes albinism

Answer 23

Defects in tyrosinase, which catalyzes the conversion of tyrosine to melanin

Question 24

Ammonia is removed as what in the brain vs peripheral tissues

Answer 24

Glutamine and glutamate in the brain (glutamate dehydrogenase)
Glutamate and alanine in peripheral tissue (using ALT)

Question 25

What happens if there is excess ammonium in the brain

Answer 25

Glutamate dehydrogenase converts a-ketoglutarate to glutamate (which is then converted to glutamine by glutamine synthetase) to use up NH4, which in turn depletes the pool of a-ketoglutarate, lowering ATP levels and leads to unconsciousness

Question 26

Where does the urea cycle occur

Answer 26

Primarily in the liver

Question 27

Ammonia toxicity side effects

Answer 27

pH imbalance, swelling of astrocytes causing cerebral edema Inhibits activity of TCA cycle because glutamate dehydrogenase is trying to get rid of ammonium by making more glutamate from a-ketoglutarate. Disruption of glutamates neurotransmitter activity because it is being converted to glutamine

Question 28

High protein vs high carb diet effects on the urea cycle

Answer 28

Urea production is increased by high protein diet and decreased by high carb diet