2nd Year DENT Lecture 1 Objectives on Amino Acid Catabolism and Transaminases
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Questions and Answers

What is the first step in amino acid catabolism?

  • Transdeamination
  • Transamination
  • Oxidative deamination
  • Deamination (correct)

    • How is free ammonia typically converted by humans for disposal?

  • Converted to ketones
  • Converted to non-essential amino acids
  • Converted to urea (correct)
  • Converted to glucose

    • What are the two main methods of amino acid deamination?

  • Transdeamination and transamination
  • Oxidative deamination and non-oxidative deamination
  • Transamination and oxidative deamination (correct)
  • Transdeamination and non-oxidative deamination

    • What are the products of oxidative deamination of L-glutamate?

    <p>Free NH3 and α-ketoacid</p> Signup and view all the answers

    How is nitrogen disposal achieved from amino acids?

    <p>Through transamination and oxidative deamination reactions</p> Signup and view all the answers

    What is the form of nitrogen excreted by humans in urine?

    <p>Urea</p> Signup and view all the answers

    Which of the following is a degradative pathway for all amino acids except lysine, threonine, and proline?

    <p>Transamination</p> Signup and view all the answers

    What is the role of transaminases enzymes in amino acid metabolism?

    <p>Transfer of ammonia between amino acids</p> Signup and view all the answers

    Where are ALT and AST enzymes mainly located in the body?

    <p>ALT - cytoplasm of liver cells; AST - cytoplasm and mitochondria of liver, heart, and skeletal muscles</p> Signup and view all the answers

    Which hormones induce the biosynthesis of transaminases enzymes?

    <p>Glucocorticoids, thyroxine &amp; growth hormone</p> Signup and view all the answers

    What is the clinical significance of increased plasma levels of ALT and AST?

    <p>Indication of acute &amp; chronic hepatitis</p> Signup and view all the answers

    What is the fate of the ammonia removed during transamination?

    <p>Converted to urea in the liver</p> Signup and view all the answers

    Which enzyme is responsible for transdeamination, combining transamination and deamination processes?

    <p>Glutamate dehydrogenase enzyme</p> Signup and view all the answers

    What is the fate of glucogenic amino acids after oxidation?

    <p>Utilized as energy sources in TCA cycle</p> Signup and view all the answers

    What is the primary source of amino acids for non-essential amino acid synthesis?

    <p>Tissue proteins breakdown</p> Signup and view all the answers

    Which type of amino acids are mainly excreted in urine as urea?

    <p>Glucogenic amino acids</p> Signup and view all the answers

    What is the major fate of amino acids from the sources mentioned in the text?

    <p>&quot;Anabolic fate&quot; - Synthesis of proteins, enzymes, and hormones</p> Signup and view all the answers

    Study Notes

    Amino Acid Catabolism

    • The first step in amino acid catabolism is deamination, which involves the removal of an amino group from an amino acid.
    • Free ammonia is typically converted to urea by humans for disposal.

    Deamination Methods

    • There are two main methods of amino acid deamination: oxidative deamination and transdeamination.
    • Oxidative deamination produces ammonia, NADH, and α-ketoglutarate as products, as seen in the deamination of L-glutamate.

    Nitrogen Disposal

    • Nitrogen disposal from amino acids is achieved through the urea cycle, where ammonia is converted to urea.

    Urea Cycle

    • The form of nitrogen excreted by humans in urine is urea.
    • The urea cycle is a degradative pathway for all amino acids except lysine, threonine, and proline.

    Transaminases Enzymes

    • Transaminases enzymes play a crucial role in amino acid metabolism.
    • ALT (alanine transaminase) and AST (aspartate transaminase) enzymes are mainly located in the liver and kidneys.
    • The biosynthesis of transaminases enzymes is induced by hormones such as glucocorticoids and thyroxine.

    Clinical Significance

    • Increased plasma levels of ALT and AST are clinically significant, indicating liver damage or disease.

    Transdeamination

    • The enzyme responsible for transdeamination is glutamate dehydrogenase, which combines transamination and deamination processes.
    • The fate of the ammonia removed during transamination is its conversion to urea in the urea cycle.

    Glucogenic Amino Acids

    • After oxidation, glucogenic amino acids are converted to glucose or ketone bodies.
    • The primary source of amino acids for non-essential amino acid synthesis is other amino acids.

    Urea Excretion

    • Essential amino acids are mainly excreted in urine as urea.
    • The major fate of amino acids from protein breakdown is their oxidation to produce energy.

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    Description

    This quiz covers the steps of amino acid catabolism, various types of deamination reactions, the importance of transaminases enzymes in biomedical and clinical settings, and methods of deamination with a focus on oxidative deamination. It also includes a discussion on Oxidative deamination with L and D Oxidases as a minor pathway.

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