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Transcript
9/29/2014 } Greek word meaning “of first importance” ◦ Most versatile molecule in the body } Protein: A polymer of amino acids ◦ Monomer: 1 of 23 different amino acids ◦ Polymer: String of many monomers ◦ Different combinations of amino acids = different proteins } Amino Acid Structure ◦ Contains an Amino Group (NH2) ◦ Contains an Acid Group (COOH) ◦ Vary only by the R Group 1 9/29/2014 1. 2. Primary Structure – Linear Amino Acid Sequence Secondary Structure – Coiled or folded shape held together by hydrogen bonds ◦ Most common secondary structures are: – Alpha helix – spring like shape – Beta helix – pleated, ribbon-like – Functional Conformation = 3 dimensional shape 3. Tertiary Structure: Further bending and folding of proteins into globular or fibrous shapes – Globular proteins – compact tertiary structure well suited for proteins that must move around freely – – – – 4. EX: Hemoglobins Fibrous proteins – slender filaments better suited for roles such as muscle contraction and strengthening the skin. EX: collogen - most abundant protein in body (connective tissue) Keratin – supports hair and skin Quaternary Structure: ◦ Association of 2 or more separate polypeptide chains ◦ Gives protein their mature (and functional) shapes 2 9/29/2014 } Conformation: unique 3-dimentional shape of a protein – Crucial to function ◦ Have the ability to reversibly change their conformation – Enzyme Function – Muscle Contraction – Opening and Closing of cell membrane pores } } Denaturation: Destroy Renaturation: Rebuild – Extreme conformational change that destroys function – Ex: Heat, pH, Salinity concentrations Due on Friday, October 3 3 9/29/2014 1. ◦ ◦ 2. ◦ ◦ 3. ◦ ◦ Provide Cell Structure EX: Keratin: tough structural protein. Give strength to hair, nails, and skin surface EX: Collagen: durable protein contained in deeper layers of skin, bones, cartilage, and teeth Communication of Cell EX: Protein hormones and other cell-to-cell signals EX: Receptors: signaling molecules bind to R’s Membrane Transport EX: Channels: in cell membrane that governs input/output EX: Carrier proteins: transports solute particles to other side of membrane – 4. ◦ Turns nerve and muscle activity “On” or “Off” Catalysis EX: Enzymes 4 9/29/2014 5. 6. 7. ◦ ◦ ◦ Recognition and Protection Ex: Immune recognition, antibodies, clotting proteins Movement EX: motor proteins: molecules with the ability to change shape repeatedly (myosin and actin filaments are responsible for muscle contraction) Cell Adhesion – – } Proteins that bind cells together Immune cells bind to cancer cells and “hangs on” until a machrophage can destroy it Keeps tissues from falling apart Enzymes: proteins that function as biological catalysts ◦ Permits reactions to occur rapidly at normal body temperature ◦ How? By lowering activation energy needed to get reaction started } } } Substrate: substance an enzyme acts upon Naming: named for substrate with –ase as the suffix (EX: amylase enzyme digests amylose (starch)) Protease? Lipase? 5 9/29/2014 } Reusability of Enzymes } Astonishing speed ◦ Enzymes are not consumed by the reactions ◦ One enzyme molecule can consume millions of substrate molecules per minute 6 9/29/2014 } Factors that affect Enzyme Function ◦ pH, salinity, and temperature } What happens? ◦ Alters or destroys the ability of the enzyme to bind to substrate ◦ Enzymes work in optimum pH – Salivary amylase works best at pH 7.0 (saliva is between 6.5 and 7.5) – Pepsin woks best at pH of 2.0 Where? ◦ Temperature optimum for human enzymes = body temp (37° C) } } Act as biological catalysts Increase the rate of chemical reaction 7 9/29/2014 } Inorganic “partners” of enzymes ◦ About 2/3 of human enzymes require a nonprotein cofactor ◦ EX: Iron, Copper, Zinc, Magnesium, Calcium ions – Many cofactors are “trace elements” } What do cofactors do? ◦ Some bind to enzymes and induce a change in shape = activates the active site } Organic cofactors derived from H2O soluble vitamins ◦ EX: Riboflavin (FADH) and Niacin (NAD+) – NAD+ is used in making some ATP ◦ Accept electrons from an enzyme in one metabolic pathway and transfer them to an enzyme in another 8