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Y1S2 002 II Biochem of Hypoglycin-A: Amino Acids and Polypeptides
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Y1S2 002 II Biochem of Hypoglycin-A: Amino Acids and Polypeptides

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Questions and Answers

What is the result of brain cells lacking glucose?

  • Coma (correct)
  • Malnutrition
  • Diabetes
  • Death due to vomiting
  • What is the scientific name of the amino acid found in the ackee?

  • Cyclopropyl acid
  • Hypoglycin-B
  • L-α-amino-β-methylene cyclopropyl propionic acid (correct)
  • Amino acid-A
  • What is the fate of the carbon skeletons of amino acids when used as fuel?

  • Formation of hormones
  • Oxidation to CO2 via TCA and conversion into glucose (correct)
  • Conversion into proteins
  • Storage in the liver
  • What is the purpose of digestion in the context of amino acid metabolism?

    <p>To break down proteins into absorbable units</p> Signup and view all the answers

    What is the term for each amino acid in a polypeptide chain?

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

    What is the role of amino acids in higher animals?

    <p>Serving as building blocks of proteins and as precursors of other biomolecules</p> Signup and view all the answers

    Where does the formation of citrulline occur?

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

    What is the enzyme responsible for forming arginino succinate?

    <p>Arginino succinate synthetase</p> Signup and view all the answers

    What is the source of the second amino group required for urea synthesis?

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

    What is the byproduct of the reaction that forms arginino succinate?

    <p>AMP and PPi</p> Signup and view all the answers

    What is the purpose of pyrophosphatase in the formation of arginino succinate?

    <p>To hydrolyze PPi to inorganic phosphate</p> Signup and view all the answers

    What is the total number of ATP molecules consumed in the formation of arginino succinate?

    <p>3</p> Signup and view all the answers

    What is the primary function of transamination during the oxidative degradation of amino acids?

    <p>To remove the amino group and convert it into a single excretory group</p> Signup and view all the answers

    What is the result of transamination on an α-amino acid?

    <p>Formation of an α-keto acid and release of ammonia</p> Signup and view all the answers

    What is the role of transaminases in transamination?

    <p>To enzymatically transfer the α-amino group from an amino acid to an α-keto acid</p> Signup and view all the answers

    What is the fate of the amino group removed during transamination?

    <p>It is converted into urea for excretion</p> Signup and view all the answers

    How many amino acids are involved in transamination during their oxidative degradation?

    <p>At least 20</p> Signup and view all the answers

    What is the reactant that receives the α-amino group during transamination?

    <p>α-Ketoglutarate</p> Signup and view all the answers

    What is responsible for the colour change in the urine of individuals with Alcaptonuria?

    <p>Autooxidation of homogentisate</p> Signup and view all the answers

    Which disease is characterized by eye and skin lesions and sometimes mental retardation?

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

    What is the effect of lack of pigmentation in the eyes of individuals with Albinism?

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

    What is the deficiency responsible for Albinism?

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

    Which disease is related to Phenylalanine?

    <p>Parkinson's disease</p> Signup and view all the answers

    What is the effect of skin sensitivity to sunlight in individuals with Albinism?

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

    What is the primary source of thyroid-stimulating hormone (TSH)?

    <p>Pituitary gland</p> Signup and view all the answers

    What is the result of iodination of tyrosyl residues in protein?

    <p>Formation of monoidotyrosine (MIT)</p> Signup and view all the answers

    Which of the following is a characteristic of thyrotoxicosis?

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

    What is the fate of monoidotyrosine (MIT) in the synthesis of thyroid hormones?

    <p>It is converted to diiodotyrosine (DIT) and then to thyroxine (T4)</p> Signup and view all the answers

    What is the significance of a low iodine content in the thyroid gland?

    <p>It leads to an underactive thyroid gland</p> Signup and view all the answers

    What is the significance of a higher proportion of triiodothyronine (T3) to thyroxine (T4)?

    <p>It indicates an overactive thyroid gland</p> Signup and view all the answers

    Study Notes

    Amino Acids and Glucose Metabolism

    • Brain cells are highly dependent on glucose; lack of glucose can lead to energy deficits and neuronal dysfunction.
    • The scientific name for the amino acid found in ackee is hypoglycin A, known for its toxic effects when consumed in unripe fruit.

    Amino Acid Fuel and Metabolism

    • Carbon skeletons of amino acids, when used as fuel, are converted into intermediates that enter the citric acid cycle for energy production.
    • Digestion is essential in amino acid metabolism to break down proteins into amino acids for absorption and subsequent usage in various bodily functions.

    Polypeptide Structure and Function

    • Each amino acid in a polypeptide chain is termed a residue, contributing to the protein's structure and function.
    • Amino acids serve various roles in higher animals, including serving as building blocks for proteins, precursors for hormones, and involvement in metabolic pathways.

    Citrulline Formation and Urea Cycle

    • Formation of citrulline occurs in the mitochondria, a key step in the urea cycle to remove excess nitrogen from the body.
    • The enzyme responsible for forming argininosuccinate is argininosuccinate synthetase, crucial for the urea synthesis pathway.

    Urea Synthesis and Byproducts

    • The second amino group required for urea synthesis is sourced from aspartate.
    • Byproduct of the reaction forming argininosuccinate is fumarate, which is utilized in the citric acid cycle.

    Role of Enzymes in Urea Cycle

    • Pyrophosphatase catalyzes the hydrolysis of pyrophosphate, driving the formation of argininosuccinate forward.
    • A total of 2 ATP molecules are consumed in the formation of argininosuccinate, reflecting energy investment in urea synthesis.

    Transamination Process

    • Primary function of transamination during oxidative degradation of amino acids is to convert non-essential amino acids to other amino acids, enabling energy production.
    • Transamination results in the conversion of an α-amino acid to a corresponding α-keto acid, facilitating amino acid interconversion.

    Enzymatic Roles in Transamination

    • Transaminases are specialized enzymes that facilitate the transfer of amino groups between amino acids and α-keto acids.
    • The fate of the removed amino group during transamination is to be incorporated into another α-keto acid, forming a new amino acid.
    • Alcaptonuria is characterized by a urine color change due to the accumulation of homogentisic acid, a byproduct of tyrosine metabolism.
    • A disease characterized by eye and skin lesions, sometimes resulting in mental retardation, is associated with phenylketonuria (PKU).
    • Lack of pigmentation in the eyes of individuals with albinism leads to increased sensitivity to light and risk of vision problems.
    • Deficiency of the enzyme tyrosinase is responsible for albinism, affecting melanin production.

    Thyroid Hormone Synthesis

    • The primary source of thyroid-stimulating hormone (TSH) is the anterior pituitary gland, regulating thyroid function.
    • Iodination of tyrosyl residues in proteins is necessary for the synthesis of thyroid hormones, impacting metabolic regulation.

    Thyrotoxicosis and Iodine Significance

    • Thyrotoxicosis is characterized by hypermetabolism, weight loss, and increased heart rate, reflecting excessive thyroid hormone levels.
    • Fate of monoidotyrosine (MIT) during thyroid hormone synthesis involves conversion to diiodotyrosine (DIT) and further coupling to form T3 and T4.

    Importance of Iodine Levels

    • Low iodine content in the thyroid gland can lead to goiter and hypothyroidism due to inadequate hormone synthesis.
    • A higher proportion of triiodothyronine (T3) to thyroxine (T4) is significant for metabolic activity, as T3 is more biologically active than T4.

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    Description

    This quiz covers the structural and functional aspects of Hypoglycin-A, a toxic compound found in ackee fruit, and its relation to amino acids, polypeptides, and enzymes. Learn about the effects of Hypoglycin-A on the body, including hypoglycemia and its consequences. Test your knowledge of biochemistry and molecular biology!

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