Protein Structure and Functions Quiz
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Questions and Answers

What is the primary role of deamination in amino acid metabolism?

  • To increase the concentration of amino acids in the plasma
  • To remove nitrogen from amino acids (correct)
  • To transport amino acids to the liver
  • To facilitate protein synthesis
  • Which of the following amino acids is considered exclusively ketogenic?

  • Leucine (correct)
  • Alanine
  • Tyrosine
  • Isoleucine
  • What categorizes an amino acid as glucogenic?

  • It can be synthesized from essential amino acids
  • It yields only ketone bodies when metabolized
  • It can be converted into glucose precursors (correct)
  • It directly participates in protein synthesis
  • Which of the following is true about non-essential amino acids?

    <p>They can be synthesized from intermediates of metabolism</p> Signup and view all the answers

    What condition is indicated by elevated levels of AST and ALT in plasma?

    <p>Liver disease</p> Signup and view all the answers

    Which of the following processes is responsible for transferring the amine group from an amino acid to $eta$-ketoglutarate?

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

    What occurs during a negative nitrogen balance?

    <p>More nitrogen is lost than taken in</p> Signup and view all the answers

    Which amino acids are excluded from the transamination process?

    <p>Lysine and Threonine</p> Signup and view all the answers

    What is one primary function of amino acids within the body?

    <p>They act as neurotransmitters and hormones</p> Signup and view all the answers

    During which metabolic state are amino acids primarily absorbed via a secondary active sodium-dependent transport system?

    <p>Fed state</p> Signup and view all the answers

    What is the significance of glucogenic and ketogenic amino acids?

    <p>They can be transformed into glucose or ketone bodies</p> Signup and view all the answers

    Which amino acids primarily serve as nitrogen carriers to the liver for the urea cycle?

    <p>Alanine and Glutamine</p> Signup and view all the answers

    What is the result of the transamination process?

    <p>Conversion of one amino acid into another through amine group transfer</p> Signup and view all the answers

    Study Notes

    Protein Structure and Functions of Amino Acids

    • Amino acids are the building blocks of proteins, essential for protein synthesis.
    • They play roles as precursors for nitrogen-containing compounds, neurotransmitters, hormones, heme, and purine/pyrimidine bases.
    • Amino acids are utilized for energy during starvation.

    Protein Digestion and Absorption

    • Protein digestion occurs during the fed state, with absorption facilitated by an active Na+-dependent transport system and facilitated transporters.

    Nitrogen Balance

    • Defined as the difference between nitrogen intake and nitrogen loss through urine, sweat, and feces.
    • Healthy adults maintain a nitrogen balance of zero.
    • A negative nitrogen balance indicates more nitrogen is lost than consumed, often due to inadequate protein intake, lack of essential amino acids, or physiological stress.
    • A positive nitrogen balance indicates more nitrogen is ingested than excreted, necessary for growth, pregnancy, and recovery from illness.

    Nitrogen Removal Processes

    • Transamination and deamination are critical for protein turnover and amino acid degradation.
    • Alanine and glutamine serve as major nitrogen carriers from muscle to the liver for the urea cycle.

    Transamination

    • Involves the transfer of an amine group from an amino acid to α-ketoglutarate, forming glutamate.
    • Catalyzed by transaminases, requiring pyridoxal phosphate (vit B6).
    • All amino acids undergo this process except lysine and threonine.
    • Diagnostic markers such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are elevated in liver diseases and certain other conditions.

    Deamination

    • The process of removing nitrogen from amino acids like glutamate and asparagine, resulting in ammonia for the urea cycle.
    • Deamination occurs in cells and gut bacteria.

    Catabolism of Amino Acids

    • Involves amino group removal and breakdown of carbon skeletons for intermediate products of metabolism.
    • Glucogenic amino acids produce pyruvate or TCA cycle intermediates, important for gluconeogenesis.
    • Ketogenic amino acids yield acetoacetate or acetyl CoA; leucine and lysine are exclusively ketogenic.

    Classification of Amino Acids

    • Glucogenic Amino Acids: Yield pyruvate or TCA cycle intermediates. Includes nonessential (e.g., alanine, asparagine) and essential amino acids (e.g., histidine, valine).
    • Ketogenic Amino Acids: Yields acetoacetate or acetyl CoA. Exclusively ketogenic amino acids include leucine and lysine.
    • Essential Amino Acids: Must be obtained through the diet.
    • Non-Essential Amino Acids: Can be synthesized in the body from glycolytic pathway intermediates and Kreb's Cycle; amino groups are added via transamination.

    Summary

    • Amino acid metabolism is essential for maintaining nitrogen balance, energy production, and protein synthesis.
    • Distinct metabolic pathways for glucogenic and ketogenic amino acids indicate their varied importance in energy and glucose homeostasis.

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    Description

    Test your knowledge on the structure and functions of amino acids, their roles in human physiology, and the intricacies of protein digestion and absorption. This quiz also covers the concept of nitrogen balance, highlighting its significance in health and nutrition.

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