Branched Chain Amino Acids, Aromatic Amino Acids etc

Question 1

What is a glucogenic AA?

Answer 1

AA that can be converted to glucose

Question 2

What are the glucogenic AA’s

Answer 2

All AA’s except leucine and lysine

Question 3

What is a ketogenic AA?

Answer 3

AA that can make ketone bodies (acetyl Co-A)

Question 4

What are the ketogenic AA’s?

Answer 4

Leucine and lysine

Question 5

What are glucogenic AAs that can also produce ketone bodies?

Answer 5

Phenylalanine
Isoleucine
Threonine
Tryptophan
Tyrosine

Question 6

What are the branch chain AAs?

Answer 6

Valine
Isoleucine
Leucine

Question 7

What are the steps involved in metabolism of branch chain AAs?

Answer 7

1. Transamination

2. Oxidative carboxylation by an a-keto acid dehydrogenase

Question 8

What is maple syrup urine disease?

Answer 8

defect in branch chain a-keto acid dehydrogenase complex

Therefore there is an accumulation of an a-keto acid

Question 9

What are the characteristics of maple syrup urine disease?

Answer 9

• odor of urine is like maple syrup

- failure to thrive, developmental delay (b/c it affects brain tissue)

Question 10

What is the therapy for maple syrup urine disease?

Answer 10

low protein diet, low in branched-chain AAs

Question 11

What is can serine be synthesized from?

Answer 11

glucose (glycolysis intermediate)

Question 12

What are the major sites of serine synthesis?

Answer 12

liver and kidney

Question 13

What is one purpose of serine?

Answer 13

Can be used as an energy source by tissues

Question 14

What can glycine be synthesized from

Answer 14

serine (also threonine which is minor)

Question 15

What does the pathway for the biosynthesis of glycine involve?

Answer 15

folic acid (CH2 acceptor) and pyridoxal phosphate

Question 16

What can glycine be converted to?

Answer 16

glyoxylate

Question 17

What are some molecules that glycine is a precursor of?

Answer 17

Creatine
Heme
Glutathione
purine nucleotides
glycochenodeoxycholate (bile salts)

Question 18

Where does synthesis of creatine begin?

Answer 18

kidney

Question 19

Where does synthesis of creatine ends?

Answer 19

liver

Question 20

Some partially synthesized creatine goes to the liver, where does this creatine go?

Answer 20

to other tissues eg heart, skeletal muscle, brain

Question 21

What is one function of creatine?

Answer 21

source of high energy phosphate to replenish ATP

Question 22

How is creatinine formed?

Answer 22

non-enzymatically
irreversibly
spontaneously
rate of formation is proportional to muscle mass

Question 23

How is creatinine excreted?

Answer 23

in urine

Question 24

What does creatinine levels in the urine tells us?

Answer 24

kidney function

muscle wasting

Question 25

Maple syrup disease leads to accumulation of: A. Glucose and fructose in the blood and urine B. Valine and leucine in the blood and urine C. Glycine in the blood and urine D. Alpha-keto acids in the blood and urine

Answer 25

D

Question 26

Glutamate is a precursor or product of which AAs?

Answer 26

Histidine Glutamine Proline Arginine

Question 27

What is GABA?

Answer 27

an inhibitory neurotransmitter

Question 28

What is the precursor of GABA

Answer 28

Glutamate

Question 29

What is one thing synthesis of GABA requires

Answer 29

Pyridoxal phosphate PLP

Question 30

What can affect the formation (failure to form) of GABA

Answer 30

low levels of vit B6

Question 31

How can ornithine form outrescine

Answer 31

by decarboxylating ornithine

Question 32

How is NO derived?

Answer 32

From the metabolism of arginine

Question 33

What is the precursor of tyrosine?

Answer 33

Phenylalanine | It is hydroxylated to form tyrosine

Question 34

What does the formation of tyrosine from phenylalanine requires?

Answer 34

tetrahydrobiopterin (BH4, synthesized in our bodies from GTP)

Question 35

What defect causes PKU?

Answer 35

defect in phenylalanine hydroxylase (phenylalanine cant be hydroxylated to form tyrosine)

Question 36

What defect causes Alkaptonuria?

Answer 36

defect in homogentisate oxidase, which causes buildup in homogentistate which darkens urine

Question 37

What defect causes Albinism?

Answer 37

defect in tyrosinase, inability to synthesize melanin pigment defect in tyrosine metabolism in melanocytes

Question 38

Phenylalanine/tyrosine are precursors for

Answer 38

Melanins (pigment molecules) | Neurotransmitters (dopamine norepinephrine, epinephrine)

Question 39

Tryptophan is a precursor for:

Answer 39

serotonin (neurotransmitter) | melatonin (circadian rhythms)

Question 40

Classical Phenylketonuria (PKU) results from a defect in phenylalanine hydroxylase. If untreated, this leads to: A. accumulation of tyrosine in the urine B. Accumulation of phenylalanine in the urine C. Accumulation of acetone in the urine D. Accumulation of phenylacetate in the urine

Answer 40

D