Biochemistry: Proteins and Their Functions
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Questions and Answers

What is the reference value range for myoglobin in males?

  • 30-90 ng/mL (correct)
  • 2% of total muscle protein
  • 100 ug/L
  • 23-50 mg/dL

    • Which condition is myoglobin levels decreased in?

  • Trisomy 21 (correct)
  • Elevated muscle injury
  • Hepatocellular carcinoma
  • Teratoblastomas

    • What is the role of troponins in muscle function?

  • Regulate actin and myosin action (correct)
  • Bind to thick filaments
  • Generate energy for muscle contraction
  • Act as structural proteins in the sarcomere

    • Which protein is synthesized by the fetal yolk sac and later by the liver?

    <p>Alpha-1 fetoprotein (AFP)</p> Signup and view all the answers

    What measurement techniques are used for alpha-1 fetoprotein (AFP)?

    <p>Immunochemical test, RIA, EIA</p> Signup and view all the answers

    What are amino acids primarily classified as?

    <p>Building blocks of proteins</p> Signup and view all the answers

    Which element is NOT found in proteins?

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

    What is the molecular structure of a typical protein?

    <p>Polymers of amino acids joined by peptide bonds</p> Signup and view all the answers

    How many common amino acids are used to construct proteins?

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

    What physiological process describes the synthesis of proteins?

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

    What is the typical range for the daily turnover of protein in the body?

    <p>125 to 220 grams</p> Signup and view all the answers

    Which statement about the composition of amino acids is true?

    <p>They differ in the chemical composition of their R groups.</p> Signup and view all the answers

    The term 'protein' derives from which language and means?

    <p>Greek, meaning first rank of importance</p> Signup and view all the answers

    What is the primary function of beta-2-microglobulin (B2M)?

    <p>It functions as a light chain component of the major histocompatibility complex.</p> Signup and view all the answers

    Which class of immunoglobulins is NOT included in the gamma globulin group?

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

    What is a characteristic of the structure of gamma globulins?

    <p>They are composed of two identical heavy chains and two identical light chains.</p> Signup and view all the answers

    Which of the following methods is NOT used to measure beta-2-microglobulin levels?

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

    In which condition are elevated levels of beta-2-microglobulin typically observed?

    <p>Impaired clearance by the kidney.</p> Signup and view all the answers

    What percentage of beta-2-microglobulin is typically reabsorbed in the proximal tubules after filtration?

    <p>More than 99%</p> Signup and view all the answers

    Which class of immunoglobulins consists of four subclasses?

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

    What is the typical composition of gamma globulins in terms of protein and carbohydrate content?

    <p>82% to 96% protein and 4% to 18% carbohydrate</p> Signup and view all the answers

    What does the Kjeldahl method primarily measure in the context of protein analysis?

    <p>Nitrogen content of protein</p> Signup and view all the answers

    What primarily distinguishes proline from other proteinogenic amino acids?

    <p>It has a secondary amine in its side group.</p> Signup and view all the answers

    Which method for protein measurement is known for having the highest analytical sensitivity?

    <p>Folin-Ciocalteu (Lowry) Method</p> Signup and view all the answers

    Which of the following amino acids is classified as a branched-chain amino acid?

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

    What is a significant advantage of the Biuret method over the Kjeldahl method?

    <p>It is the most widely used method</p> Signup and view all the answers

    What type of conditions are associated with increased levels of complement in the bloodstream?

    <p>Inflammatory conditions</p> Signup and view all the answers

    What does the tertiary structure of a protein refer to?

    <p>The specific folding and bending into a 3D configuration.</p> Signup and view all the answers

    What is the primary characteristic of the quaternary structure of a protein?

    <p>Combining multiple polypeptide chains into a complex unit.</p> Signup and view all the answers

    Which of the following reagents is NOT used in the Biuret method?

    <p>Phosphotungstic-molybdic acid</p> Signup and view all the answers

    Which scenario is likely to increase glycoproteins in response to acute inflammation?

    <p>During severe burns.</p> Signup and view all the answers

    What does the end product of the Biuret method typically look like?

    <p>Violet-colored chelate</p> Signup and view all the answers

    Which measurement technique for complement levels can be automated?

    <p>Both A and B</p> Signup and view all the answers

    Which amino acids are examples of unique amino acid sequences?

    <p>Lysine, Arginine, Histidine</p> Signup and view all the answers

    What role do cross-linked C-Telopeptides (CTXs) play in medical diagnostics?

    <p>Assessing bone turnover</p> Signup and view all the answers

    Which protein structure is best described as a 'pleated sheet' or coil?

    <p>Secondary Structure</p> Signup and view all the answers

    Which of the following is NOT a characteristic of quaternary structure?

    <p>Has a single defined shape.</p> Signup and view all the answers

    What is the primary reason proteins absorb light at 210 nm?

    <p>Absorbance of peptide bonds</p> Signup and view all the answers

    Which protein component migrates first in serum protein electrophoresis?

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

    The term 'gamma spike' in an abnormal serum protein electrophoresis pattern is indicative of which condition?

    <p>Plasma cell myeloma</p> Signup and view all the answers

    What is the principle behind the refractometry method for serum total protein analysis?

    <p>Measurement of refractive index</p> Signup and view all the answers

    What substance is used in turbidimetric and nephelometric methods for measuring serum proteins?

    <p>Sulfosalicylic acid</p> Signup and view all the answers

    Which component is typically found in the alpha-2-globulin band during serum protein electrophoresis?

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

    Beta-gamma bridging in serum protein electrophoresis is associated with which health condition?

    <p>Hepatic cirrhosis</p> Signup and view all the answers

    What does a flat curve in the alpha-1-globulin band suggest during serum protein electrophoresis?

    <p>Juvenile cirrhosis</p> Signup and view all the answers

    Study Notes

    Amino Acids

    • Amino acids are molecules with an amine group, a carboxylic acid group, and a variable side chain (R group).
    • Essential amino acids cannot be produced by the body and must be obtained from food.
    • Non-essential amino acids can be synthesized by the body.
    • Key elements: carbon, hydrogen, oxygen, and nitrogen.
    • Building blocks of proteins; vital for many biological molecules.
    • Mnemonic for essential amino acids: PVT TIM HALL (Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Leucine, Lysine)
    • Short hand symbols for Amino Acids are used in sequence data.

    Proteins

    • Proteins are polymers composed of amino acids linked by peptide bonds.
    • Average protein contains 200-300 amino acids.
    • Crucial for nearly all bodily functions.
    • Involved in enzyme activity, transport, growth, support, motion, and immune response.
    • Nitrogen balance: positive nitrogen balance occurs when protein anabolism is greater than catabolism (growth/repair). Negative nitrogen balance occurs when protein catabolism exceeds anabolism (burns, disease).
    • Four major groups of amino based on polarity/charge: nonpolar/hydrophobic, uncharged polar, acidic, basic.
    • Four levels of protein structure: primary (linear sequence), secondary (coils & sheets), tertiary (3D folding), and quaternary (multiple polypeptide chains).

    Classification of Proteins

    • Simple proteins: only amino acids upon hydrolysis.
    • Conjugate proteins: protein + non-protein moiety. Lipoproteins, metalloproteins, glycoproteins, nucleoproteins.
      • Classified according to shape:
        • Globular: spherical, mobile, dynamic functions (enzymes, hormones).
        • Fibrous: elongated, structural functions (collagen, keratin).
      • Classified according to solubility: Albumin (water-soluble); Globulin (water-insoluble, weak salt soluble); Albuminoids (insoluble).

    Plasma Proteins: Specific Examples & Functions

    • Prealbumin (Transthyretin/TBPA): transports retinol, thyroxine, and triiodothyronine.
    • Albumin: most abundant plasma protein, maintains osmotic pressure, transports various substances.
    • Alpha-1-antichymotrypsin: serine protease inhibitor, important in inflammation.
    • Alpha-2-macroglobulin: large plasma protein.
    • Haptoglobin: binds free hemoglobin, preventing loss in urine- key function in evaluating intravascular hemolysis.
    • Transferrin (Siderophilin): transports ferric iron.
    • Alpha-1-antitrypsin (AAT): a major component of alpha-1 globulin fraction; inhibits enzymes.
    • Fibrinogen: essential for blood clotting.
    • Gamma globulins (immunoglobulins/antibodies): crucial part of the immune system.
    • Beta-2-microglobulin (B2M): part of the major histocompatibility complex (HLA).
    • Alpha-1-fetoprotein (AFP): fetal serum protein (tumor marker).
    • Ceruloplasmin: copper-containing protein.
    • Lipoproteins: transport cholesterol, triglycerides, phospholipids (HDL, LDL, VLDL).
    • Myoglobin: heme protein in muscle tissue.
    • Troponins (TnT, TnI, TnC): heart muscle proteins, markers for myocardial infarction (AMI).
    • Group-specific component globulin (Gc-globulin)
    • Alpha-1-acid glycoprotein (orosomucoid)
    • Fibronectin
    • C-reactive protein
    • Complement: proteins in the immune response.

    Measurement of Proteins

    • Kjeldahl method: measures nitrogen content.
    • Biuret method: widely used; measures peptide bonds.
    • Folin-Ciocalteu (Lowry) method: highly sensitive; measures phenolic compounds.
    • Ultraviolet absorption method: measures absorbance at specific wavelengths.
    • Serum protein electrophoresis (SPE): separates proteins based on charge.
    • Refractometry: measures refractive index of serum solutes.
    • Turbidimetric/Nephelometric methods: measure light scattering from a precipitate.
    • Salt fractionation: separates proteins based on solubility.

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    Description

    This quiz covers key concepts in biochemistry related to proteins, including their synthesis, structure, and various types of proteins found in the body. Explore topics like myoglobin levels, amino acid classification, and the functionality of immunoglobulins. Test your knowledge on the important roles these biomolecules play in physiological processes.

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