Nitrogen

Question 1

Transamination Info

Answer 1

Process of removing one NH3 from one amino acid and put on another with creation of alpha keto acid.

Cofactor = PLP (Vit B6); schiff base: enzyme’s Lys episilon - NH2 binds to carbon of PLP aldehyde group -> DBond

Question 2

Transamination usual

Answer 2

Glu, Ala, Asp usually used. Glu to alpha-ketoglutarate, Ala to pyruvate, Asp to OAA

Reversible and active in liver, Liver dmg look for ALT and AST.

AA1 and a-keto2 to AA2 and a-keto1

Question 3

Deamination

Answer 3

Release free NH3.

Enzyme = Glutamate Dehydrogenase (Glu is only AA that accepts free NH2)

Glu =(NADh and Nh3) a-ketoglutarate

NADH = ATP synth; NADPH = biosynth

Question 4

Toxic NH3

Answer 4

needs to be removed
number 1 source = Gln; enzyme = glutaminase
removed via urea cycle

Question 5

Step 1 Urea cycle

Answer 5

In mito
Free NH3 and HCO3 to carbomyl phosphate
Enz= carbomyl phosphate synthase 1, rqrs 2 ATP
Allosteric activation by N-acetyl-glutamate (act by Arg)

Question 6

Step 2 Urea Cycle

Answer 6

Carbomyl phosphate and Ornithine to Citrulline

Enz = Ornithine Transcarbomylase (OTC)

Question 7

OTC def

Answer 7

Hyperammonemia, Orotic acid build up, loss of ATP (due to diversion of alpha ketoglutarate from TCA cycle in order to soak up NH3, Glu to Gln via glutamine synthetase requires ATP so more lost)
Hepaticencephalopathy

Question 8

Step 3 Urea cycle

Answer 8

Citrulline leaves mito to cytosol
Citrulline and Asp to Arginosuccinate
Asp provides second NH3
Enz = Arginosuccinate synthetase, rqrs ATP

Question 9

Urea Cycle energy rqr

Answer 9

4 ATP equivalents

Question 10

Urea Cycle Step 4

Answer 10

Arginosuccinate to Arg and Fumarate
Enzyme = arginosuccinate lyase
Some Arg used for feedback to CPS1, Fumarate to TCA cycle via conversion to malate

Question 11

Urea cycle Step 5

Answer 11

Arg to Ornithine and Urea
Enz = Arginase
urea to urine, ornithine to mito for reuse

Question 12

BUN

Answer 12

Liver dmg = decreased BUN
Kidney dmg = increased BUN
Tx = alternate N extract = Benzoic acid, phenylacetate, phenylbutyrate. Conjugates with gly and gln to make H20 soluble

Question 13

Draw Urea Cycle

Answer 13

On paper

Question 14

Nitrogen after meal stomach

Answer 14

pepsin breaks up some proteins to AA

Question 15

Nitrogen after meal SI

Answer 15

Trypsin, chymotrypsin, elastase, carboxy peptides A and B finish job. Breaks to AA or di/tripeptide AA

Question 16

Nitrogen after meal to blood

Answer 16

Via Sodium dependent transporters.

Exception = BCAA and Aromatic AA (all essential so absorbed asap)

Question 17

Nitrogen after meal Liver disperse

Answer 17

To musc for build: BCAAs to M for energy catabolism

Stay in liver for energy production via gluconeogenesis and plasma proteins

Kidney for excretion

Question 18

AA’s during fast

Answer 18

Ala and Gln will go back to liver for energy prod via gluconeo, this removes NH2 (to urea cycle)

Question 19

Protein Degrade

Answer 19

Determined by half life
shortest = PEST (Pro, Glu, Ser, Thr)
methods = ubiquitin proteosome and Calpain (Calcium dependent self destruction)

Question 20

N balance

Answer 20

Pos = NH3 in > loss for growth and preg
Neg = NH3 in < loss for trauma, cancer, starve

Question 21

AA’s as energy

Answer 21

All are glucogenic except Leu and Lys = ketogenic

AA’s both gluc and keto = Aromatics (Tyr, Phe, Trp) and Ile

Question 22

Diet Induced Thermogenesis

Answer 22

Specific Dynamic action - energy required to break down substrate (prot>fat>carbs)

Resp Quotient: amt CO2 prd/ O2 cons, more carbs = higher RQ. C=1, fats = .66, prots = .8)