• BIO 180
  • UNIT 1. INORGANIC CHEMISTRY
  • UNIT 2. INTERMOLECULAR FORCES, WATER, AND ACIDS AND BASES
  • UNIT 3. CARBOHYDRATES
  • UNIT 4. LIPIDS, NUCLEIC ACIDS, AND PROTEINS
  • UNIT 5. CELL MEMBRANES-STRUCTURE AND CELL FUNCTION
  • UNIT 6. PROKARYOTES AND VIRUSES
  • UNIT 7. ENERGY BALANCE
  • UNIT 8. GLYCOLYSIS AND CITRIC ACID CYCLE
  • UNIT 9. ELECTRON TRANSPORT CHAIN
  • UNIT 10. PHOTOSYSNTHESIS
  • UNIT 11. CELLULAR TRANSPORT AND CELLULAR SIGNALING
  • UNIT 12. CELL DIVISION AND CANCER
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  • 4.3

    Proteins

    Of the four classes of biological molecules, the proteins are the most diverse in their functions. By some estimates, cells make more than 50,000 different proteins, with each protein having a specific job. With such diversity, what gives a protein its functionality and specificity? For proteins, form is function. In other words, the specific 3-dimensional shape of a protein is what allows it to do its job. Table 1 lists some of the major functions of proteins, but this list is not exhaustive. In fact, it is hard to think of any function in the body in which proteins are not integral.

    Function

    Example

    Structure

    Collagen in tendons and ligaments, Keratin in the nails and skin

    Transport

    Hemoglobin in the blood, Na+, K+-ATPase in cell membranes

    Protection

    Antibodies of the immune system

    Movement

    Actin and Myosin in muscles

    Enzymes

    Digestive enzymes in the small intestine (Lactase, Sucrase, Trypsin)

    Receptors

    Membrane proteins that respond to chemical messengers (insulin receptors)

    Regulation

    Chemical messengers: hormones, neurotransmitters, cytokines

    Amino AcidsAmino Acid StructurePeptide Bonds and PolypeptidesProtein StructureClasses of ProteinsEnzymes

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