Amino acid metabolism: Oxidation and Urea test 3

Question 1

what is the process of removing ammonia from the body called?

Answer 1

the urea cycle

Question 2

why are amino acids important?

Answer 2

because they are coded for the DNA and they make up proteins

Question 3

what are the four fates of dietary AAs

Answer 3

• protein syn
• Energy production (CAC) (15-20% of total energy)
• Biosynthesis
• Urea excretion

Question 4

what are the three drivers of Protein oxidation?

Answer 4

normal synthesis and degradation
protein rich diet
starvation or diabetes mellitus

Question 5

what is the cycle that connects the urea cycle to the CAC?

Answer 5

Aspartate-arginino-succinate shunt of the CAC

Question 6

what bonds(AAs) does pepsin target

Answer 6

phenylalanine
tyrosine
tryptophan

Question 7

secretin does what?

Answer 7

stimulates release of bicarbonate from the pancreas

Question 8

what does cholecystokinin do?

Answer 8

stimulates zymogen release from the pancreas

Question 9

three fates of dietary protein enzymatically degraded to AAs?

Answer 9

protein synthesis
catabolized for energy within cells
transported to the liver and excreted

Question 10

dietary proteins cause what to be released from the stomach?

Answer 10

gastrin from G cells, which causes chief cells to release pepsinogen and parietal cells to release HCl

Question 11

where does most of the AA catabolism happen?

Answer 11

in the liver

basic strategy is to separate the amine group, and leave the carbon chain

Question 12

what are the metabolically important AAs

Answer 12

Glutamine, Glutamate, Aspartate, Alanine

• Amine group carriers
• precursors and common metabolites
• entry and exit molecules from the CAC

Question 13

How is ammonia toxic?

Answer 13

• it disrupts the Na/K ATPase in the CNS.
• astrocyte K uptake is disrupted
• high extracellular K prevents GABA(too much Cl in side cell)

Question 14

how are amine groups stabilized?

Answer 14

urea or uric acid for excretion

Question 15

in the transaminase rxn between alpha-ketogluterate and glutamate what enzyme does it and what stabilizes the amine group?

Answer 15

PLP-pyridoxal phosphate

Vitamine B6

Question 16

when an AA transfers its amino group to alpha ketogluterate what is left?

Answer 16

alpha keto acid

Question 17

what are the two major AA catabolism rxns?

Answer 17

transaminase and one-carbon transfers

Question 18

what enzyme is responsible for glutamate becoming glutamine?

Answer 18

glutamine synthase

Question 19

why is glutamine important?

Answer 19

non-toxic
most cells have glutamine synthetase
common synthetic precursor

Question 20

how is intracellular ammonia buffered?

Answer 20

by converting glutamate to glutamine

Question 21

what is the glucose-alanine cycle?

Answer 21

-pyruvate gets an amine group add by
alanine anminotransferase and becomes alanine.
-the amino group is coming from glutamate
-alanine then adds the amine group to alpha-ketogluterate in the liver which becomes glutamate and pyruvate is now in the liver.

Question 22

why is the glucose-alanine cycle important?

Answer 22

allows for proteins to function as a energy source
occurs in anaerobic stress
coincides with the cori cycle

Question 23

what is the purpose of the urea cycle?

Answer 23

to excrete liver nitrogen in the form of Urea

• requires enzymes within the mitochondria and cytoplasm
• four steps (five structural changes)
• ATP-dependent

Question 24

what AA is absolutely essential for the urea cycle?

Answer 24

ornithine

Question 25

what is the first step in the urea cycle?

Answer 25

Glutamine from the extrahepatic tissue
Alanine from the muscle
these the become gluatamate

Question 26

once glutamate is in the mitochondrial matirx what happens?

Answer 26

glutamate then release ammonia to become carbamoyl phosphate
or
the amine group is added to oxaloacetate to become asparate

Question 27

when ornithine adds an amine group to carbamoyl phosphate what is produced?

Answer 27

citrulline

**this occurs in the mitochondria

Question 28

citrulline gets another amine group from aspartate and becomes what?

Answer 28

• arginine, **ATP dependent
• when this reacts with water urea is formed and we get ornithine once again.
• this occurs in the cytoplasm

Question 29

what are the two levels of regulation for the urea cycle?

Answer 29

in the urea cycle itself and in the precursor step of making carbamoyl phosphate

Question 30

where in the body are AAs glucogenic and ketogenic?

Answer 30

in the liver and only the liver

Question 31

what are the six AAs degraded to pyruvate?

most energy rich

Answer 31

tyrptophan
alanine
cysteine
serine
glycine
threonine

Question 32

what are the seven AAs degraded to Acetyl-
CoA?
second most energy rich

Answer 32

tryptophan
lysine
phenylalanine
tyrosine
luecine
isoleucine
threonine

Question 33

what are the five AAs degraded into alpha-ketogluterate?

3rd most energy rich

Answer 33

glutamate
glutamine
proline
arginine
histidine

Question 34

four AAs degraded to become Succinyl-CoA?

4th most energy rich

Answer 34

methionine
isoleucine
valine
threonine

Question 35

what AAs are degraded to become oxaloacetate?

least energy rich

Answer 35

Asparagine and Asparate

Question 36

what are the non essential AAs?

Answer 36

Alanine
Asparagine
Aspartate
Glutamate
Serine

Question 37

what AAs are essential (always essential) 
his
isometeric
leg
lifts
met
failure
three 
tries
valiantly

Answer 37

histidine   
isoluecine
leucine
lysine
methionine
phenylalanine
threonine
tryptophan
valine

Question 38

which AAs are conditionally essential?

Answer 38

arginine
cysteine
glutamine
glycine
proline
tyrosine

Question 39

how is urea removed from body?

Answer 39

bile and urea