Proteins Proteins make up more than 50% of the dry weight of cells Proteins are instrumental almost all aspects of an organisms life

Structural Proteins Function Example Support Collagen & elastin in animal connective tissues Keratin in hair, horns & feathers

Storage Proteins Function Example Storage of amino acids Ovalbumin in egg whites stores amino acids for developing embryo Casein in mammal milk is a major source of amino acids for baby mammals

Transport Proteins Function Example Transport of other substances Hemoglobin transports oxygen from the lungs to other parts of the body Proteins transport molecules across cell membranes

Hormonal Proteins Function Example Coordination of an organism’s activities Insulin regulates the concentration of sugar in the blood of vertebrates

Receptor Proteins Function Example Response of cell to chemical stimuli Receptors built into the membrane of a nerve cell detect chemical signals from other nerve cells

Contractile & Motor Proteins Function Example Movement Actin & myosin are responsible for the movement of muscles Cilia & flagella

Defensive Proteins Function Example Protection against disease Antibodies combat bacteria & viruses

Enzymatic Proteins Function Example Catalyze chemical reactions Digestive enzymes catalyze the hydrolysis of polymers in food

Protein Structure Monomers of amino acids bond together to form polymers called polypeptide chains Amino acidspolypeptideprotein

Primary Structure: A sequence of amino acids

Secondary Structure: Twisting or bending of the polypeptide chain

Tertiary Structure: Three dimensional, folded structure

Fig. 5-21e Tertiary Structure Quaternary Structure

A ribbon model of lysozyme A space-filling model of lysozyme Fig. 5-19 Groove Groove (a) A ribbon model of lysozyme (b) A space-filling model of lysozyme

Hydrophobic interactions and van der Waals interactions Polypeptide Fig. 5-21f Hydrophobic interactions and van der Waals interactions Polypeptide backbone Hydrogen bond Disulfide bridge Ionic bond

Quaternary Structure: When two or more polypeptides fold together

Denature To cause a protein to lose its shape Caused by acid, base, temperature etc

Enzyme A molecule that catalyzes (speeds up) a chemical reaction Most enzymes are proteins

Substrate The reactant being catalyzed Example: The enzyme, amylase requires the substrate, starch.