Fates Of Amino Acid Carbon Skeletons

Question 1

Glucogenic vs ketogenic amino acids

Answer 1

. Most glucogenic and go towards forming glucose
. Ketogenic go to making ketones/FAs
. Only amino acids that are ketogenic: Leu, Lys

Question 2

What is the major AA for hepatic gluconeogenesis

Answer 2

Ala

Question 3

What is the major AA for gluconeogenesis in kidney?

Answer 3

Glu

Question 4

Glucogenic AAs are metabolized into what intermediates?

Answer 4

. Pyruvate 
. Alpha-ketoglutarate
. Succinyl-CoA 
. Fumarate
. Oxaloacetate

Question 5

Thr can be metabolize dinto what intermediates?

Answer 5

Pyruvate or succinyl-CoA

Question 6

What AA can be metabolized to form Pyruvate

Answer 6

. Ala 
. Cys
. Ser
. Thr
. Trp

Question 7

What AA ca be metabolized into oxaloacetate?

Answer 7

Asp

Asn

Question 8

What AA can be metabolized to form fumarate

Answer 8

Asp
. Phe
. Tyr

Question 9

What AA can be metabolized to formed alpha-ketoglutarate?

Answer 9

. Arg
. Glu
. Gln
. His
. Pro

Question 10

Glucose-Ala cycle

Answer 10

. Transamination of pyruvate w/in muscle forms Ala
. Ala removed from blood by liver, serves as AA substrate for gluconeogenesis
. N released from Ala converted into urea for urine excretion
.

Question 11

Glu accounts for what percentage of endogenous glucose production in kidneys?

Answer 11

20-25%

Question 12

Besides glucose synthesis, what other functions does Glu have?

Answer 12

. Carb metabolism
. Stimulation of gluconeogenesis
. glycogen storage in muscle
. Selective conversion to glucose in patients w/ type II DM

Question 13

Number of AA capable of forming percursors for ketone bodies and lipid

Answer 13

6, but only 2 are exclusively ketogenic, the other form intermediately during catabolism capable of entering gluconeogenesis

Question 14

Branches chain amino acids

Answer 14

. Leu, Iso, Val
. Hydrophobic 
. Play role in proteins w/ transmembrane domains 
. Make up 20% AA in dietary protein 
. 35% daily essential AA requirement
. Forms Gln in the brain

Question 15

Catabolism of branched chain AA

Answer 15

Occurs in skeletal muscle (50% whole body) and small portion in liver after absorption from intestine (10-15%)
. Branched-chain aminotransferase (BCAT) and branched chain alpha-ketoacid dehydrogenase (BCKD) are 1st 2 steps in catabolism of all BCAAs

Question 16

T/F glucose/ketone. Body metabolic fuels is not the major determinant of BCAA catabolism

Answer 16

T

Question 17

BCAAs in regards to obesity

Answer 17

. Anti-obesity effect via nutrient signaling
. Obese individuals have higher BCAA serum
. High BCAA may be predictive of DM type II risk

Question 18

Inter-organ AA metabolism in fed state

Answer 18

. Glu and Gln used for energy in intestinal cells
. Other AA released into blood and travel o liver
. Liver: synthesis of plasma proteins and conversion to glucose or TAGs
. Muscles: protein synthesis, BCAA catabolized or incorporated into protein/muscle, BCAA maintains Glu, Gln, and Ala in muscle

Question 19

Inter-organ metabolism of AA in fasted state

Answer 19

. Muscle major source of plasma AAs Gln and Ala
. Gluconeogenesis through Ala in liver and Gln in kidney
. Liver: ketogenic AA metabolized for ketones
. Intestine: Gln catabolized for energy in intestinal cells

Question 20

In BCAA pathway Leu forms ____ while Val and Iso form _____

Answer 20

. Acetyl-CoA

. Succinyl CoA