Protein degradation and the urea cycle #18

Question 1

nitrogen is excreted by the

Answer 1

urea cycle

Question 2

extracellular and intracellular proteins are degraded by

Answer 2

lysosomal proteases

Question 3

ubiquitin can be called a

Answer 3

proteasome

Question 4

amino acids form

Answer 4

heme, nucleotides, cofactors, creatine

Question 5

what are the major roles of proteolysis

Answer 5

~activation of enzymes, prohormones
~blood clotting/complement cascades
~control of organ growth
~digestion of dietary compounds
~fuel supply
~maintenance of the amino acid pool
~regulation of enzyme activity
~amyloidogenesis
~tissue repair

Question 6

the most rapidly degrade enzymes all occupy control pints which are

Answer 6

the enzymes rate of degradation is as imp as its rate of synthesis

Question 7

lysosomes contain

Answer 7

proteases like cathepsins

Question 8

lysosomes have an internal pH of

Answer 8

5, this contributes to protection of the cell via compartmentation

Question 9

in well nourished cells lysosomal protein degradation is

Answer 9

non selective

Question 10

in starving cells lysosomal proteolysis targets

Answer 10

KFERQ motifs in the liver and kidney

Question 11

regression of the uterus after childbirth is an ex of

Answer 11

lysosome dependent tissue remolding

Question 12

protein degradation via ubiquitin

Answer 12

~ N end rule: Asp, Arg, Leu, Lys, Phe have half lives of 2-3 min
~ Ala, Gly, Met, Ser, Thr, Val have half lives of >20hrs
~ proteins with Pro, Glu, Ser, Thr are rapidly degraded
~E1 - only one gene in humans, E2 - >20 genes in humans, E3 - HECT(28) domain and RING finger (616)

Question 13

transamination

Answer 13

interconverts an amino acid and an alpha-keto acid

Question 14

oxidative deamination of glutamate releases

Answer 14

ammonia

Question 15

amino acids

Answer 15

are not stored in the cell

Question 16

transamination is done by which enzyme

Answer 16

transaminases / aminotransferases

Question 17

alpha-ketoglutarate and oxaloacetate acts as

Answer 17

amino group acceptors, thus forming glutamate and aspartate

Question 18

aspartate can be converted to

Answer 18

glutamate

Question 19

glutamate is - to alpha-ketoglutarate and NH3 by -

Answer 19

oxidatively deaminated

glutamate DH

Question 20

the C backbone of amino acids is used for

Answer 20

ATP synthesis, glucose, FA, ketone bodies synthesis

Question 21

where is GDH -glutamate DH
what inhibits it
what activates it

Answer 21

-in the mitochondria
-GTP and NADH
- ADP and NAD+
IT IS THE ONLY ENZYME THAT CAN ACCEPT NAD+ OR NADP+ AS ITS COENZYME

Question 22

the overall urea cycle

Answer 22

aspartate +3ATP= urea and fumarate

Question 23

carbamoyl synthetase I, is activated by

Answer 23

is in the mito., uses ammonia as is N doner, used in urea biosynthesis.
activated by N-acetylglutamate

Question 24

carbamoyl synthetase II

Answer 24

is in the cytosol and used glutamine as is N doner, is involved in pyrimidine synthesis