Amino Acid Metabolism

Question 1

What is the amino acid pool?

Answer 1

“The total supply of free amino acids in the body available for protein synthesis and other metabolic functions.”

Question 2

How do amino acids enter the amino acid pool?

Answer 2

“Through dietary intake

Question 3

What is transamination?

Answer 3

“The transfer of an amino group from an amino acid to a keto acid

Question 4

Which coenzyme is required for transamination?

Answer 4

“Pyridoxal phosphate (PLP)

Question 5

What is the role of glutamate in transamination?

Answer 5

“Glutamate acts as the main amino group donor and receiver in transamination reactions.”

Question 6

What is deamination?

Answer 6

“The removal of an amino group from an amino acid

Question 7

Which enzyme catalyzes oxidative deamination?

Answer 7

“Glutamate dehydrogenase.”

Question 8

What is the fate of ammonia produced in deamination?

Answer 8

“Ammonia is converted into urea in the liver and excreted by the kidneys.”

Question 9

Why is transamination important?

Answer 9

“It allows amino groups to be transferred to different keto acids

Question 10

What is the difference between transamination and deamination?

Answer 10

“Transamination transfers an amino group to another molecule

Question 11

Which amino acid acts as a nitrogen carrier in transamination?

Answer 11

“Glutamate.”

Question 12

What is the significance of the amino acid pool?

Answer 12

“It provides amino acids for protein synthesis

Question 14

What is oxidative deamination?

Answer 14

“The removal of an amino group from an amino acid with the production of ammonia and a keto acid

Question 15

Which enzyme catalyzes oxidative deamination?

Answer 15

“Glutamate dehydrogenase.”

Question 16

What is the main product of oxidative deamination?

Answer 16

“Ammonia (NH3) and α-ketoglutarate.”

Question 17

Where does oxidative deamination occur?

Answer 17

“Mostly in the liver and kidneys.”

Question 18

What is the significance of oxidative deamination?

Answer 18

“It helps in the removal of excess nitrogen and provides α-keto acids for energy metabolism.”

Question 19

What is non-oxidative deamination?

Answer 19

“The removal of an amino group without oxidation

Question 20

Which enzymes are involved in non-oxidative deamination?

Answer 20

“Serine dehydratase and threonine dehydratase.”

Question 21

What is the cofactor required for non-oxidative deamination?

Answer 21

“Pyridoxal phosphate (PLP).”

Question 22

What are the products of non-oxidative deamination?

Answer 22

“Ammonia (NH3) and α-keto acids like pyruvate or α-ketobutyrate.”

Question 23

How does non-oxidative deamination differ from oxidative deamination?

Answer 23

“Non-oxidative deamination does not require NAD+ or NADP+ and often involves dehydratases instead of dehydrogenases.”

Question 24

Why is non-oxidative deamination important?

Answer 24

“It helps break down amino acids like serine and threonine without using an oxidation step.”

Question 25

Front

Answer 25

Back

Question 26

What is a transamination reaction?

Answer 26

The transfer of an amino group from an amino acid to a keto acid, producing a new amino acid and a new keto acid.

Question 27

What is the role of transamination in amino acid metabolism?

Answer 27

It helps in the synthesis of non-essential amino acids and the redistribution of nitrogen for excretion.

Question 28

What is the key enzyme involved in transamination?

Answer 28

Aminotransferases (transaminases), e.g., ALT (alanine aminotransferase) and AST (aspartate aminotransferase).

Question 29

What coenzyme is required for transamination reactions?

Answer 29

Pyridoxal phosphate (PLP), the active form of vitamin B6.

Question 30

What is the clinical significance of ALT and AST?

Answer 30

They are liver enzymes; elevated levels indicate liver damage (e.g., hepatitis, cirrhosis).

Question 31

What is the difference between ALT and AST?

Answer 31

ALT is more specific to the liver, while AST is found in the liver, heart, muscle, and other tissues.

Question 32

What is the role of transamination in the urea cycle?

Answer 32

It provides aspartate, which donates nitrogen for urea synthesis.

Question 33

What is the importance of transamination in gluconeogenesis?

Answer 33

It converts amino acids into keto acids, which can enter gluconeogenesis (e.g., alanine → pyruvate).

Question 34

What is the alanine-glucose cycle?

Answer 34

Alanine transports nitrogen from muscles to the liver, where it is converted to pyruvate for gluconeogenesis.

Question 35

What is the significance of glutamate in transamination?

Answer 35

Glutamate is a central molecule in transamination, as it collects and donates amino groups.

Question 36

What is the role of transamination in amino acid catabolism?

Answer 36

It removes amino groups from amino acids, allowing the carbon skeleton to be used for energy or biosynthesis.

Question 37

What is the clinical significance of elevated ALT/AST in alcoholic liver disease?

Answer 37

AST is typically higher than ALT (AST:ALT ratio >2).

Question 38

What is the clinical significance of elevated ALT/AST in viral hepatitis?

Answer 38

ALT is typically higher than AST (ALT > AST).

Question 39

What is the role of transamination in the synthesis of non-essential amino acids?

Answer 39

It allows the synthesis of amino acids like alanine, aspartate, and glutamate from their corresponding keto acids.

Question 40

What is the relationship between transamination and vitamin B6 deficiency?

Answer 40

Vitamin B6 deficiency impairs transamination, leading to decreased amino acid synthesis and increased amino acid catabolism.

Question 41

What is the role of transamination in the metabolism of branched-chain amino acids (BCAAs)?

Answer 41

BCAAs (leucine, isoleucine, valine) undergo transamination in muscle to form branched-chain keto acids.

Question 42

What is the clinical significance of transamination in maple syrup urine disease (MSUD)?

Answer 42

Defective transamination of BCAAs leads to accumulation of toxic keto acids, causing neurological damage.

Question 43

What is the role of transamination in the synthesis of neurotransmitters?

Answer 43

It helps synthesize glutamate (excitatory neurotransmitter) and GABA (inhibitory neurotransmitter).

Question 44

What is the role of transamination in the synthesis of purines and pyrimidines?

Answer 44

It provides nitrogen for the synthesis of nucleotide bases.

Question 45

What is the clinical significance of transamination in liver function tests (LFTs)?

Answer 45

Elevated ALT and AST levels indicate hepatocellular injury.

Question 46

What is the role of transamination in the Cori cycle?

Answer 46

It helps convert lactate to pyruvate, which can then enter gluconeogenesis.

Question 47

What is the role of transamination in the synthesis of alanine?

Answer 47

Alanine is synthesized from pyruvate via transamination, using glutamate as the amino donor.

Question 48

What is the role of transamination in the synthesis of aspartate?

Answer 48

Aspartate is synthesized from oxaloacetate via transamination, using glutamate as the amino donor.

Question 49

What is the role of transamination in the synthesis of glutamine?

Answer 49

Glutamine is synthesized from glutamate via glutamine synthetase, not transamination.

Question 50

What is the clinical significance of transamination in chronic liver disease?

Answer 50

Persistent elevation of ALT/AST indicates ongoing liver damage and impaired synthetic function.

Question 51

What is the role of transamination in the metabolism of aromatic amino acids?

Answer 51

It helps convert phenylalanine to tyrosine, which is then used for neurotransmitter synthesis.