Nitrogen Metabolism

Question 1

5 normal forms of nitrogen excretion

Answer 1

Urea
Uric acid
Ammonia
Urobilinogen
Creatinine

Question 2

Where does creatinine come from?

Answer 2

Breakdown of creatine phosphate in muscles

Question 3

Where does uric acid come from?

Syndrome w/ uric acid build-up?

Causes what?

Answer 3

Purine breakdown

Lesch-Nyhan Syndrome

Gout, hyperuricosuria, hyperuricemia

Question 4

Reasoning behind ammonia poisoning

Answer 4

Excess ammonia in the blood uses up alpha-KG and ATP to get rid of it, thus taking away from the TCA cycle and compromising energy source for the brain

Question 5

Describe the general amino acid pathway through the body

Answer 5

Absorbed by GI mucosa or synthesized de novo

Put into the general A.A. pool

Used in protein build-up/break down OR degraded

Used as glucogenic/ketogenic building blocks OR put into the urine

Question 6

Amino acids put into the urine get there via what forms?

Answer 6

Ammonia –> urea

Question 7

Hartnup Disease

Answer 7

Defective neutral non-polar A.A. transporter (mucosa and tubules)

Very low levels of tryptophan, etc in the body

Question 8

Cysteinuria

Amino acids affected?

Causes what?

Answer 8

Defective dibasic amino acid transporter

Cys, Lys, Arg

Crystal formation (stones)

Question 9

Amino acids that require THF for metabolism

Answer 9

Methionine ONLY

Question 10

Amino acids that require THB for metabolism

Answer 10

Phe, Tyr, Trp

Question 11

What are the branched chain amino acids?

Answer 11

Valine
Isoleucine
Leucine

Question 12

What disease is associated with the inability to digest branched chain AA’s?

Enzyme?

Answer 12

Maple Syrup Urine Disease

Alpha keto acid dehydrogenase

Question 13

What is the common product of the breakdown of Met and branched-chain amino acids?

Significance?

Answer 13

Succinyl CoA

TCA cycle intermediate
Heme metabolism

Question 14

A patient has Homocysteinuria. What is the patient at risk for?

What processes will be affected?

Answer 14

Atherosclerosis

TCA cycle and heme metabolism

Question 15

Why do exercisers supplement with branched chain amino acids?

Answer 15

Succinyl CoA is the byproduct, thus more of it will increase TCA cycle ability and thus energy creation

Question 16

What is the first intermediate of Met breakdown?

Answer 16

SAM

Question 17

What is THF needed for in Methionine metabolism?

What else is needed?

Answer 17

Recycling of Homocysteine into Methionine

B6, B12

Question 18

What are the co-enzymes needed for breakdown of branched chain amino acids?

Answer 18

Thiamine, CoA, FAD, lipoic acid, NAD

Question 19

A baby patient has urine that smells of burnt sugar, like syrup. It’s found that the cause is simply a deficiency of a co-factor. What is the co-factor?

What is the enzyme?

Answer 19

Thiamine (TPP)

Alpha keto acid dehydrogenase

Question 20

What are the 3 diseases to worry about with Phe metabolism?

Answer 20

PKU
Alkaptonuria
Tyrosinemia type 1

Question 21

What does Phe need for conversion to Tyr?

Answer 21

THB

Question 22

A patient is diagnosed with secondary Phenylketonuria (PKU). What is the cause of the problem?

What is the result?

Answer 22

Deficiency in THB, thus can’t convert Phe to Tyr for metabolism

Excess Phe converted to phenyl ketones, which are found in the urine

Question 23

A baby patient is diagnosed with Alkaptonuria. What is the result of this?

How is this typically diagnosed?

Answer 23

Homogentisate builds up, thus converts into alkaptones

Urine is blue/black due to alkaptones in the urine

Question 24

What is the end product of Phe metabolism?

Significance?

Answer 24

Fumarate

Another TCA intermediate, thus contributing to energy creation

Question 25

A patient is diagnosed with Tyrosinemia type 1. What is the result? Danger?

Answer 25

Build-up of fumarylacetoacetate Excess converts to succinyl acetone Extremely toxic to liver and kidneys

Question 26

A patient has a deficiency in THB. What is the likely cause? What metabolic issues does this cause?

Answer 26

Purine metabolism is impaired, thus THB is not created Phe, Trp, and Tyr metabolism is also impaired

Question 27

A patient has Hartnup Disease. What substances will NOT be able to be made as well as a result? Why?

Answer 27

NAD/NADP Serotonin Melatonin Made via metabolism of tryptophan, which is low in serum

Question 28

How is melatonin made in amino acid metabolism? Enzyme?

Answer 28

Trp --> serotonin --> melatonin MAO (2nd step)

Question 29

What co-enzyme is produced from tryptophan? Intermediate? Needs what?

Answer 29

NAD+/NADP+ Niacin Vitamin B6

Question 30

Breakdown pathway of Tyr

Answer 30

``` Tyr Dopa Dopamine NE Epinephrine ```

Question 31

What all can be made from tyrosine?

Answer 31

Catecholamines Melanin Thyroid hormones

Question 32

A patient has a pheochromocytoma. What is likely to be found in the urine? Why?

Answer 32

Homovanillic acid (HVA) Vanillylmandelic acid (VMA) Breakdown products of dopamine and norepinephrine, respectively

Question 33

What is MAO needed for in amino acid breakdown? COMT?

Answer 33

Serotonin, dopamine, NE, Epi metabolisms All those minus serotonin

Question 34

In what condition is uric acid most dangerous? Why?

Answer 34

In acidic urine of distal tubule and cause kidney stones Most likely to crystalize in acidic environment

Question 35

How is urea actually formed? Precursor needed to drive the cycle?

Answer 35

Released from the conversion of Arg --> ornithine (using H2O) in the urea cycle Carbamoyl phosphate

Question 36

What 2 things require carbamoyl phosphate?

Answer 36

Drive the urea cycle Pyrimidine synthesis

Question 37

What two syndromes are important in terms of heme degradation?

Answer 37

Gilbert syndrome Cholestasis

Question 38

A patient has lots of conjugated bilirubin in his urine. What is the name of the disease? What does the urine look like?

Answer 38

Cholestasis Very dark yellow

Question 39

A patient has trouble conjugating bilirubin, thus he has a build-up of unconjugated bilirubin. What is the disease called?

Answer 39

Gilbert Syndrome