22 Questions
What is the enzyme responsible for converting γ-glutamyl-cysteine to cysteine?
γ-Glutamylcysteine synthetase
What is the consequence of a deficiency in glutathione synthetase enzyme?
Increased levels of 5-oxoproline in blood and urine
What is the role of γ-glutamyl transpeptidase in the γ-glutamyl cycle?
To transfer γ-glutamyl group from glutathione to an amino acid
What is the function of pepsinogen in protein digestion?
To convert into active enzyme
What is the source of amino acids in the amino acid pool?
Both dietary proteins and non-essential amino acids synthesized in the body
What is the byproduct of the reaction catalyzed by oxoprolinase?
Glutamic acid
How are amino acids absorbed from the small intestine?
Through active transport mechanism using a carrier protein
What is the energy source for the sodium-amino acid carrier system?
Energy from Na/K+ pump
What is the function of the Na/K+ pump in amino acid absorption?
To pump sodium out of the cell
Where are amino acids absorbed from in the digestive system?
Small intestine
What is the result of protein digestion in the stomach?
Large peptides and some free amino acids
What is the primary fate of the products resulting from deamination?
Excretion in urine
What is the role of transamination reactions in amino acid catabolism?
To transfer the amino group from one amino acid to another
What is the byproduct of oxidative deamination reactions?
Ammonia and alpha-keto acid
What is the purpose of the catabolic pathway of amino acids?
To break down amino acids into energy
Which of the following compounds is involved in transamination reactions?
Alpha-ketoglutarate
What is the primary function of the amino acid pool?
To provide a source of amino acids for various bodily functions
What is the byproduct of the transamination reaction between glutamic acid and pyruvic acid?
α- keto glutarate
Which enzyme catalyzes the transamination reaction between glutamic acid and oxaloacetic acid?
Aspartate transaminase (AST)
What is the diagnostic value of transaminases in the blood?
They are normally intracellular enzymes and elevated levels indicate cell damage
What does an increase in the level of both ALT and AST indicate?
Damage to liver cells
What does an increase in the level of AST alone suggest?
Damage to heart muscle, skeletal muscle, or kidney cells
Study Notes
Amino Acid Pool and Catabolism
- Amino acids can be categorized into essential and non-essential amino acids
- Non-essential amino acids can be synthesized in the body
- Catabolism of amino acids occurs through deamination, which involves the removal of the amino group
- Deamination can occur through oxidative deamination, transamination, or transdeamination
- Oxidative deamination involves the oxidation and deamination of amino acids to form α-keto acids and ammonia
- Transamination involves the transfer of an amino group from one α-amino acid to an α-keto acid to form a new α-amino acid and a new α-keto acid
- Transdeamination involves the removal of the amino group from an amino acid to form an α-keto acid and ammonia
Amino Acid Absorption
- Amino acids are absorbed from the small intestine through passive and active transport mechanisms
- The carrier protein transport system (sodium-amino acid carrier system) is an active transport mechanism that uses energy from the Na+/K+ pump
- The glutathione transport system (γ-glutamyl cycle) is another active transport mechanism
- Oxoprolinuria is an inherited disorder caused by a deficiency of glutathione synthetase, leading to increased levels of 5-oxoproline in the blood and urine, acidosis, and neurological damage
Protein Digestion and Absorption
- Proteins are denatured by gastric HCl and then broken down into large peptides and some free amino acids by pepsin
- Large peptides are further broken down into smaller peptides and free amino acids
- Amino acids are absorbed from the small intestine through passive and active transport mechanisms
- The absorbed amino acids are transported to the liver through the portal blood
Transamination and Transaminases
- Transaminases are enzymes that catalyze the transfer of an amino group from an α-amino acid to an α-keto acid
- Examples of transaminases include alanine transaminase (ALT) and aspartate transaminase (AST)
- ALT catalyzes the reaction between glutamic acid and pyruvic acid to form alanine and α-keto glutarate
- AST catalyzes the reaction between glutamic acid and oxaloacetic acid to form aspartic acid and α-keto glutarate
- Transaminases are elevated in the blood when there is damage to cells that produce these enzymes, such as liver cells, heart muscle cells, or skeletal muscle cells
This quiz covers the process of protein digestion, including the role of enzymes and gastric HCL, and the absorption of amino acids in the small intestine. It explains how proteins are broken down into smaller peptides and amino acids, and how these are absorbed into the bloodstream.
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