PROTEINS Proteins Protein functions: enzyme (catalyst) defense transport
PROTEINS Proteins Protein functions: enzyme (catalyst) defense transport support motion regulation
storage 7 Classes of Proteins Structural Transport Spider silk
Hemoglobin Mammal hair Signal Fibers of tendons and lipids Some hormones Contractile Chemical catalyst
Muscular movement Enzymes Storage Egg white
Defense Antibodies Structure is related to function! Structurally sophisticated. Shape determines function and is crucial to the job of a protein. Composed of amino
acids joined together by peptide bonds. 20 types of amino acids Made at the ribosomes in a cell. Monomer: Amino Acids
(AA) contain an amino group (-NH2), a carboxyl group (-COOH) and a hydrogen atom, all bonded to a central carbon atom twenty common AA grouped into five classes based on side groups
nonpolar AA polar uncharged AA charged AA aromatic AA
special-function AA Structural Formulas for the 20 Amino Acids Amino Acids Peptide bond links two amino acids. A protein is composed of one or more long chains of amino acids linked by peptide bonds (dipetide and polypeptides).
The Polypeptide Backbone Amino acids joined together end-to-end COOH of one AA covalently bonds to the NH 2 of the next AA Special name for this bond - Peptide Bond Two AAs bonded together Dipeptide Three AAs bonded together Tripeptide Many AAs bonded together Polypeptide Characteristics of a protein determined by
composition and sequence of AAs Virtually unlimited number of proteins Protein Structure Protein function is determined by its shape. The shape is driven by a number of noncovalent interactions such as hydrogen bonding, ionic interactions, Van der Waals
forces and hydrophobic packing. Protein structure primary - specific amino acid sequence secondary - folding of amino acid chains Protein Structure tertiary - final folded shape of
globular protein quaternary forms when two or more polypeptide chains associate to form a functional protein Summary: Levels of Structure Primary:
Literally, the sequence of amino acids A string of beads (up to 20 different colors) Secondary: The way the amino acid chain coils or folds Describing the way a knot is tied Tertiary: Overall three-dimensional shape of a polypeptide Describing what a knot looks like from the outside Quaternary: Consists of more than one polypeptide
Like several completed knots glued together Levels of Protein Organization Examples of Fibrous Proteins Protein-folding Diseases Assembly of AAs into protein extremely complex Process overseen by chaperone molecules Inhibit incorrect interactions between R groups as
polypeptide grows Defects in these chaperones can corrupt the tertiary structure of proteins Mad cow disease could be due to mis-folded proteins Other protein folding errors: Alzheimer's and Cystic Fibrosis Enzymes
Enzymes are proteins that function as a catalyst - they control the rate of a reaction without being consumed by the reaction. They usually speed up the rate of a reaction by lowering the amount of activation energy needed to start the reaction. End with -ase.
Ex. lactase Reaction with enzyme How enzymes workInduced Fit Model The substrate (what the enzyme is going to work upon) comes into contact with the active site of the enzyme.
The enzyme wraps around the substrate breaking or forming bonds. The product is released. Enzyme at work Double Check Which one is the enzyme? How do you know?
Unfolding Proteins Denaturation refers to the process of changing a proteins shape. usually rendered biologically inactive salt-curing and pickling used to preserve food temperature - high temperatures break bonds. pH - designed to work at a specific pH!
Examples You can not use fresh pineapple in jello but you can used canned! Why? Pepsin is an enzyme that helps break down proteins in the stomach during digestion. It works at a pH of 2! Trypsin is an enzyme that helps break down proteins as well. It works in the intestines with a pH of 8.
Many snake venoms are enzymes that work when directly injected into blood or tissue (pH = 7.4). If swallowed, they are denatured by the acidity of the stomach! (Dont try it, just take my word for it!) Why do people without refrigeration salt their food for long term storage? Regulating Enzymes Non-competitive inhibitors
Compound which binds to some other area, called the allosteric site, not the active site. This causes a change in the shape of the active site. The substrate no longer fits! Usually temporary, allows the body to control the production of many chemicals. Example: Nerve gas! http://www.bbc.co.uk/education/asguru/bio logy/02biologicalmolecules/01proteins/11e
nzymes/05enzymes_d/index.shtml Competitive Inhibitors Blocks the active site so the substrate can not get to it! This is usually permanent inhibition Ex. DDT blocks the site of enzymes of the nervous system. Penicillin blocks enzymes used by bacteria to produce the cell wall, stopping bacterial
reproduction! http://www.bbc.co.uk/education/asguru/biology/02 biologicalmolecules/01proteins/11enzymes/04enzy mes_c/index.shtml Competitive Inhibitor Example Ethanol is metabolized in the body by oxidation to acetaldehyde, which is in turn further oxidized to acetic acid by aldehyde oxidase enzymes. Normally, the second
reaction is rapid so that acetaldehyde does not accumulate in the body. A drug, disulfiram (Antabuse) inhibits the aldehyde oxidase which causes the accumulation of acetaldehyde with subsequent unpleasant side-effects of nausea and vomiting. This drug is sometimes used to help people overcome the drinking habit.
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