Final - AA metabolism

Question 1

In amino acid catabolism, what part of the a.a. do we remove/where does it go? & what part do we utilize?

Answer 1

Remove Nitrogen (amine group) which gets excreted as Urea
Utilize the C-skeleton by: oxidation in Citric Acid Cycle, conversion to glucose (gluconeogenesis), and conversion to fat (via acetyl-CoA)
(135)

Question 2

What does the removal of the amino group on an amino acid require? (3 steps)

Answer 2

Transamination
Oxidative Deamination
Urea synthesis
(135)

Question 3

What is the alpha-keto form of Aspartate? of Glutamate? of Alanine?

Answer 3

Aspartate = Oxaloacetate (OA = KC intermediate)
Glutamate = alpha-ketoglutarate (KC intermediate)
Alanine = Pyruvate
(136-137)

Question 4

What is the amino acid form of oxaloacetate? of alpha-ketogluterate? of Pyruvate?

Answer 4

Oxaloacetate = aspartate
Alpha-ketogluterate = glutamate
Pyruvate = alanine
(136-137)

Question 5

What is the purpose of transamination?

Answer 5

Interconverting amino acids
Shuttling -NH3 groups to glutamate and aspartate (which sets things up for entry into the urea cycle)
(137)

Question 6

All clinical lab tests use what pair of substrate/product and what coenzyme?

Answer 6

Glutamate and alpha-Ketogluterate as substrate/product
Pyridoxal Phosphate = coenzyme
(137)

Question 7

What is the purpose of oxidative deamination?

Answer 7

Production of NH4+ (ammonia)

139

Question 8

What are the products of oxidative deamination of glutamate?

Answer 8

NH4 and alpha-Ketogluterate

139, 136

Question 9

The Urea Cycle (a.k.a. Krebs-Henseleit Cycle) is most important in what part of the body?

Answer 9

Liver
*=site of urea synthesis
(141)

Question 10

Which enzyme regulates the urea cycle?

Answer 10

Carbamoyl Phosphate Synthetase

142

Question 11

What is the last enzyme in the Urea cycle?

Answer 11

Arginase
(bottom part of Arginine becomes urea)
(142)

Question 12

True or False: Alanine is a non-useful amino acid to transfer N+ to the liver and kidneys for excretion?

Answer 12

False; Alanine IS a useful amino acid to transfer N+ to kidneys and liver
(143)

Question 13

After removal of amino groups, the alpha-Keto acids are available for what?

Answer 13

1) Synthesis via gluconeogenesis or fatty acid & ketone synthesis
2) Oxidation
(144)

Question 14

Which type of amino acids must be converted to Acetyl-CoA?

Which amino acids are they?

Answer 14

Ketogenic
Leucine and Lysine
(144)

Question 15

What is the name for amino acids that are converted to pyruvate or other KC intermediates?
How many are there?

Answer 15

Glucogenic amino acids
18/20 a.a. are glucogenic
*alanine, aspartate, glutamate, glutamine … etc
(144)

Question 16

What does a positive nitrogen balance indicate?

What does a negative nitrogen balance indicate?

Answer 16

+ balance requires a net synthesis of tissue proteins (growth period/pregnancy)
- balance requires a net catabolism of tissue proteins (starvation, decrease CHO, increase N+ extreted0
(146)

Question 17

Does intake of CHO favor a more positive N-balance or a negative one?

Answer 17

Positive (protein sparing effect)

146

Question 18

What is the result of pyruvate undergoing transamination?

Answer 18

Alanine

147

Question 19

What do you get when oxaloacetate undergoes transamination?

Answer 19

Aspartate

147

Question 20

Which amino acid pathway conversion is limited in Phenylketonuria (PKU)? What is the resulting effect?

Answer 20

Limited conversion of phenylalanine to tyrosine. Phe is converted to ketone by-products (phenylpyruvate or phenylketones) = can cause retardation and death by age 30
(150)

Question 21

What amino acid abnormal pathway disorder occurs because of decreased tyrosinase?

Answer 21

Albinism (decreased melanin)

150

Question 22

Which amino acid abnormal pathway disease is correlated with decreased homogentisate oxidase?

Answer 22

Alcaptonuria
-urine turns black
-causes problem in tyrosine/phe catabolism
(150)

Question 23

What is the defective enzyme in PKU (phenylketonuria), Albanism, Alcaptonuria?

Answer 23

PKU = phenylalanine hydroxylase
Albinism = tyrosinase
Alcaptonuruia = homogentisate oxidase
(150)