Lec 4 Macromolecules (II) 1-6

Lec 4 Macromolecules (II) 1-6 - Biol 113 AU2011 A Proteins...

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1 Biol 113 AU2011 Lecture 4 Macromolecules (II) A. Proteins B. Nucleic acids A. Proteins Proteins account for more than 50% of the dry mass of most cells Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances Figure 5.15-a Enzymatic proteins Defensive proteins Storage proteins Transport proteins Enzyme Virus Antibodies Bacterium Ovalbumin Amino acids for embryo Transport protein Cell membrane Function: Selective acceleration of chemical reactions Example: Digestive enzymes catalyze the hydrolysis of bonds in food molecules. Function: Protection against disease Example: Antibodies inactivate and help destroy viruses and bacteria. Function: Storage of amino acids Function: Transport of substances Examples: Casein, the protein of milk, is the major source of amino acids for baby mammals. Plants have storage proteins in their seeds. Ovalbumin is the protein of egg white, used as an amino acid source for the developing embryo. Examples: Hemoglobin, the iron-containing protein of vertebrate blood, transports oxygen from the lungs to other parts of the body. Other proteins transport molecules across cell membranes. Figure 5.15-b Hormonal proteins Function: Coordination of an organism’s activities Example: Insulin, a hormone secreted by the pancreas, causes other tissues to take up glucose, thus regulating blood sugar concentration High blood sugar Normal blood sugar Insulin secreted Signaling molecules Receptor protein Muscle tissue Actin Myosin 100 μ m 60 μ m Collagen Connective tissue Receptor proteins Function: Response of cell to chemical stimuli Example: Receptors built into the membrane of a nerve cell detect signaling molecules released by other nerve cells. Contractile and motor proteins Function: Movement Examples: Motor proteins are responsible for the undulations of cilia and flagella. Actin and myosin proteins are responsible for the contraction of muscles. Structural proteins Function: Support Examples: Keratin is the protein of hair, horns, feathers, and other skin appendages. Insects and spiders use silk fibers to make their cocoons and webs, respectively. Collagen and elastin proteins provide a fibrous framework in animal connective tissues.
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