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Clinical Chemistry 1: Proteins & Non-Protein Compounds

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30 Questions

What is the percentage of nitrogen in proteins that differentiates them from carbohydrates and lipids?

16%

What type of bond is formed between the carboxyl group of one amino acid and the amino group of another amino acid?

Peptide bond

Which level of protein structure involves the formation of alpha helixes and beta sheets?

Secondary structure

What is the term for the end of a protein structure with a free amino group?

N-terminal

What is the term for the interactions between the R groups of amino acids that fold a polypeptide chain into a three-dimensional structure?

Tertiary structure interactions

What is the level of protein structure that involves the binding of two or more folded polypeptide chains?

Quaternary structure

What function do some cellular proteins perform?

Acting as receptors for hormones

What is the primary site of plasma protein synthesis?

Liver

What happens to amino acids when proteins degrade?

They undergo deamination and are converted to urea

What is the function of collagen?

To maintain the structure of body parts

What is the result of cytokines released at the site of injury or inflammation?

Increased synthesis of acute-phase reactant proteins

What is the function of enzymes?

To accelerate chemical reactions

What is the primary function of immunoglobulins?

To destroy foreign antigens

Which of the following conditions may cause hyperproteinemia?

Monoclonal gammopathies

What is prealbumin an indicator of?

Nutritional status

What is a possible cause of hypoproteinemia?

Gastrointestinal tract inflammation

What is albumin responsible for in the blood?

Binding many analytes for transport

Which protein is synthesized in the liver and has the highest concentration of all plasma proteins?

Albumin

Which protein is involved in the removal of free hemoglobin?

Haptoglobin

What is the primary function of ceruloplasmin?

Copper-containing enzymatic activity

In which condition is α2-macroglobulin decreased?

Acute inflammatory disorders

What is the primary function of transferrin?

Transporting iron

What is C-reactive protein (CRP)?

An acute-phase reactant

Which of the following is an immunoglobulin?

IgG

What is the principle behind refractometry in protein analysis?

The change in velocity of light as it passes through the boundary between air and water

What is the complex formed in the biuret method?

Cupric-peptide bond complex

What is the purpose of the Kjeldahl technique?

To validate materials used with the biuret method

What is the principle behind the dye binding technique?

The formation of a protein-dye complex that results in a shift of the maximum absorbance of the dye

What is the pH of the buffer used in serum protein electrophoresis?

pH 8.6

What is the term for the technique that separates proteins based on their size and charge?

Electrophoresis

Study Notes

Characteristics of Proteins

  • Proteins are macromolecules made of amino acids, linked via peptide bonds.
  • Proteins consist of 16% nitrogen, differentiating them from carbohydrates and lipids.
  • N-terminal: End of protein structure with a free amino group.
  • C-terminal: End of protein structure with a free carboxyl group.

Protein Structure

  • Primary structure: Amino acids linked through covalent peptide bonding in a specific sequence.
  • Secondary structure: Polypeptide chain winds to form alpha helixes and beta sheets through hydrogen bonds.
  • Tertiary structure: Coiled polypeptide chain folds to form a 3D structure through R group interactions.
  • Quaternary structure: Two or more folded polypeptide chains bind to form a functional protein.

Types of Proteins

  • Antibodies: Proteins that protect the body against "foreign" invaders.
  • Cellular proteins: Function as receptors for hormones.
  • Structural proteins: Collagen is the fibrous component that maintains body structure.
  • Enzymes: Catalysts that accelerate chemical reactions.

Plasma Total Protein Regulation

  • The liver synthesizes most plasma proteins.
  • Plasma cells synthesize immunoglobulins.
  • Proteins are synthesized from amino acids, with one amino acid linked to another through peptide bond formation.
  • When proteins degrade, their constituent amino acids undergo deamination with ammonia formation, converted to urea for excretion in urine.

Clinical Significance of Major Proteins

  • Prealbumin (Transthyretin): Indicator of nutritional status, transports thyroid hormones.
  • Albumin: Synthesized in the liver, binds many analytes for transport, contributes to plasma osmotic pressure.
  • α1-Acid glycoprotein (orosomucoid): Acute-phase reactant, binds to basic drugs.
  • Haptoglobin: α2-globulin that binds free hemoglobin, acute-phase reactant.
  • Ceruloplasmin: α2-globulin, copper-containing protein with enzymatic activity, acute-phase reactant.
  • α2-Macroglobulin: Proteolytic enzyme inhibitor, increased in nephrotic syndrome, contraceptive use, pregnancy, and estrogen therapy.
  • Transferrin: β-globulin that transports iron.
  • C-Reactive Protein (CRP): β-globulin, acute-phase reactant, increased in tissue necrosis, infections, and inflammation.
  • Immunoglobulins: Antibodies, synthesized in plasma cells as an immune response.

Methodology for Serum Total Protein, Albumin, and Protein Fractionation

  • Refractometry: Based on the change in velocity of light, proportional to the concentration of solutes (proteins) present in serum.
  • Biuret method: Based on cupric ions complexing with peptide bonds in an alkaline medium, producing a purple-colored complex.
  • Dye binding: Proteins bind to a dye, forming a protein-dye complex that results in a shift of the maximum absorbance of the dye.
  • Kjeldahl: Based on the quantification of the nitrogen content of protein, considered the reference method of choice.
  • Electrophoresis: Serum protein electrophoresis, serum is applied in the cathode region of an agarose gel or cellulose acetate plate saturated with a buffer of pH 8.6.

Test your understanding of proteins and non-protein compounds in clinical chemistry. This quiz covers the characteristics of proteins, including their structure and bonding.

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