10/12 Energy from Proteins

Question 1

what can all 20 AAs be broken down into

Answer 1

pyruvate
acetyl-CoA
TCA intermediate

Question 2

what molecules picks up the amine group in transamination rxns

Answer 2

a-ketoglutarate —> glutamate

Question 3

product of transamination rxn

Answer 3

a-keto acid

Question 4

hormones of fasted state and effects

Answer 4

when blood glucose and insulin are low, counter regulatory hormones are released (glucagon, cortisol, (nor)epinepherine

mm do not have glucagon receptors

Question 5

where do breakdown products go after leaving mm/peripheral tissues

Answer 5

alanine/glutamine –> liver

BCAAs and glutamine –> small intestines and kidneys

Question 6

which AAs are major blood nitrogen carriers

Answer 6

alanine and glutamine

Question 7

what product of AA metabolism is toxic

Answer 7

ammonia (from glutamate)
eliminated through urea cycle

can cross blood-brain barrier, interferes with neurotransmitters

Question 8

which AA are exclusively ketogenic

Answer 8

leucine and lysine

Question 9

what happens to ketogenic AAs

Answer 9

come to liver, converted into Acetyl-CoA (or acetylacyl-CoA), can then become a fatty acid (TAGs)

Question 10

what happens to glutogenic AAS

Answer 10

come to liver, converted to pyruvate or oxaloacetate (or other TCA intermediates), can then become glucose (glycogen)

Question 11

two enzymes for transamination

Answer 11

transaminase

aminotransferase

Question 12

which aminotransferase enzymes are on a standard serum panel to check for liver damage

Answer 12

ALT (alanine aminotransferase) (liver prob)

AST (aspartate aminotransferase) (liver or muscle prob)

Question 13

prefered E sources in fed state

Answer 13

glucose and FAs

AAs are used for synthetic processes

Question 14

what are the BCAAs

Answer 14

leucine, isoleucine, valine

Question 15

cofactor for BCAA transamination

Answer 15

B6

Question 16

cofactor for further breakdown of BCAAs

Answer 16

B1 (thiamine)

Question 17

products of further breakdown of BCAAs

Answer 17

NADH, FADH2, acetyl-CoA, succinyl-CoA

Question 18

cofacts req for biosynthesis of succinyl-CoA

Answer 18

(B1/thiamine)
B7 biotin
B12 cobalamin

Question 19

what enzyme is deficient in maple syrup urine disease

Answer 19

AR loss of branched-chain keto acid dehydrogenase

Question 20

maple syrup urine disease, symptoms/Tx

Answer 20

by day 4-7 of life, accumulation of BCAAs causing sweet-smelling urine, progressive neuro damage, seizures, spastic quadriparesis

Tx: dietary restrictions of BCAAs

Question 21

role of blood alanine

Answer 21

to liver, converted to pyruvate for gluconeogenesis

enzyme: ALT

Question 22

role of blood glutamine

Answer 22

to liver: urea cycle (most nitrogen disposal)

to kidneys: to be eliminated as ammonium (maintains urine and blood pH)

Question 23

location of urea cycle

Answer 23

liver, mitochondria then cytoplasm

Question 24

accumulation of first nitrogen in urea cycle

Answer 24

enzyme: carbamoyl phosphate synthatase I, reqs E, in mitochondria
product: carbamoyl phosphate

Question 25

accumulation of second nitrigen in urea cycle

Answer 25

enzyme: ornithine transcarbamoylase, reqs E, sends prod to cytoplams
product: citrulline

Question 26

final product of urea cycle

Answer 26

urea (two N)

from arginine

Question 27

lab value for renal failure

Answer 27

high BUN (blood urea nitrogen)

Question 28

lab value for liver problems

Answer 28

high ammonia

Question 29

ornithine transcarbamoylase deficiency

Answer 29

x-linked
chronically elevated blood ammonia results in neuronal damage and mental retardation
Tx: low protein diet, dialysis
Labs: high ammonia, low BUN, respiratory alkalosis, low citrulline