proteins

• Proteins are a large class of nitrogenous organic compounds
• Composed of long chains of amino acids linked together by amide links or peptide bonds
• Proteins are found in every cell in the body
• Our bodies need dietary proteins to supply amino acids for growth & repair/maintenance of worn out tissues
• The sequence of amino acids in proteins is determined by DNA
• Proteins play crucial roles in the structure, function, and regulation of cells and tissues
• The smallest functional unit (monomer) of proteins is the amino acid
• Functions of proteins include:

  • Enzymes: Catalyze chemical reactions in the body
  • Structural Proteins: Provide support and shape to cells and tissues
  • Transport Proteins: Carry molecules across cell membranes
  • Hormones: Act as chemical messengers to regulate physiological processes
  • Antibodies: Defend against foreign substances
  • Receptors: Transmit signals triggering cellular responses
• Physical properties of proteins include solubility, size and shape, and flexibility
• Chemical properties of proteins involve amino acids, condensation reaction, denaturation, and hydrolysis
• Amino acids are the building blocks of proteins
• There are 20 different amino acids, with 9 classified as essential
• Classification of amino acids includes nonpolar (hydrophobic), polar (hydrophilic), charged, and aromatic amino acids
• Isoelectric point is the pH at which an amino acid ionizes
• Primary Structure of proteins:

  • Refers to the linear sequence of amino acids forming the polypeptide chain
  • The exact sequence of amino acids determines the final fold and function of the protein
• Secondary Structure of proteins:

  • Identified by local folded structures within the polypeptide chain
  • Stabilized by hydrogen bonds
  • Major arrangements include α-helix, β-pleated sheet, and triple helix
• Tertiary Structure of proteins:

  • Refers to the overall 3-D structure of proteins
  • Stabilized by hydrogen bonds, electrostatic (ionic) forces, disulphide bonds, and van der Waals forces
  • Results in fibrous and globular molecular shapes
• Quaternary Structure of proteins:

  • Composed of several amino acids making polypeptide chains
  • Stabilized by various bonds and connections
  • Example: hemoglobin, G-protein
• Haemoglobin as a globular protein:

  • Consists of four polypeptide chains with heme groups
  • Oxygen binds to iron atoms in hemoglobin
• Collagen as a fibrous protein:

  • Main structural protein in connective tissues
  • Forms collagen helix in connective tissues like cartilage, bones, tendons, ligaments, and skin
• Denaturation of proteins:

  • Process where a protein loses its 3D structure and function
  • Can be caused by heat, pH, chemicals, or agitation
  • Denaturation can be reversible or irreversible
• Effects of heat on proteins:

  • High temperatures lead to denaturation by disrupting non-covalent bonds
  • Denaturation can be reversible if the protein regains structure
• Relationship between water and proteins:

  • Water plays roles in protein structure and interactions
  • Water participates in catalytic functions of proteins
  • Water interacts with protein surface and interior
• Enzymes called proteases catalyze the hydrolysis of peptide bonds during protein digestion
• Proteins are composed of long chains of amino acids joined together via peptide bonds
• Proteins are produced through transcription of DNA and translation of RNA