Popular in Cell Biology
Popular in Biology
This 4 page Class Notes was uploaded by Sarah Ferrier on Sunday September 27, 2015. The Class Notes belongs to BSC322 at Marshall University taught by Dr. Harrison in Fall 2015. Since its upload, it has received 78 views. For similar materials see Cell Biology in Biology at Marshall University.
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I was sick all last week and these notes were exactly what I needed to get caught up. Cheers!
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What is Karma?
Karma is the currency of StudySoup.
Date Created: 09/27/15
Week 5 Chapter 6 Enzymes Catalysts of Life 1 Km1 gt v quot VmaXIS Vmax gt When it is plotted as 1v versus 1S the resulting doublereciprocal plot is linear in the general algebraic form y mx b where m KmVmax is the slope and b 1Vmax is the yintercept I Xintercept is 1Km I Vmax can be determined directly from the reciprocal of the yintercept and Km from the negative reciprocal of the xintercept Act either irreversibly or reversibly Influenced mostly inhibited by products alternative substrates substrate analogues drugs toxins and a very important class of regulators called quotallosteric effectors gt Enzyme inhibition plays vital role as a control mechanism in cells is important in the action of drugs and poisons useful to enzymologists as tools in their studies of reaction mechanisms and to doctors for treatment of disease VV I Binds to enzyme covalently causing permanent loss of catalytic activity I Usually toxic to cells 0 Ions of heavy metals 0 Nerve gas poisons 0 Some insecticides I Binds to an enzyme in a noncovalent dissociable manner such that the free and bound forms of the inhibitor exist in equilibrium with each other I bind active site of enzyme and compete with substrate for active site 0 Activity inhibited directly because active sites are bound to inhibitors preventing substrate from binding 0 Same Vmax as uninhibited reaction but Km changed I bind enzyme molecule outside of the active site 0 Inhibit activity indirectly by causing a conformation change 0 Same Km as uninhibited reaction but Vmax changed 9 gt Changes in amino acid sequence alters conformation of active binding site leads to loss of function or altered function gt Mutant enzyme cannot catalyze its specific reaction and excess of substrates accumulate with no end products produced I Tay Sachs disease 0 Cells lack hydrolase that normally break down a membrane component gt Rates must be continuously adjusted to keep them tuned to needs of cell Regulation depends on interactions I Changes in substrate and product concentrations I Alterations in temperature and pH I Presence and concentration of inhibitors o Interactions of substances and products with the enzyme Cells can turn enzymes on and off by allosteric regulation and covalent modification I Allosteric enzymes are regulated by molecules other than reactants and products Feedback inhibition Also regulated by addition or removal of chemical groups I Phosphorylationdephosphorylation o Reversible addition of phosphate group gt Enzymes have 2 conformations I One form where enzyme has a high affinity for its substrates leading to high activity I Other form has little or no affinity for its substrate giving little to no catalytic activity Inhibitors shift equilibrium between two enzyme states to favor low affinity form Activators favor high affinity form of the enzyme I Inactive in its uncomplexed form I Activator stabilizes enzyme Large multisubunit proteins with an active site or allosteric site on each unit Chapter 3 Macromolecules of the cell gt gt gt gt Not formed by same type of linear polymerization as proteins nucleic acids polysaccharides Regarded as macromolecules because of high molecular weight and importance in cellular structures particularly membranes Main 6 classes I Fatty acids I Triacylglycerols I Phospholipids I Glycolipids I Steroids I Terpines Hydrophobic nature thus little affinity for water I Readily soluble in nonpolar solvents Relatively few polar groups but some are amphipathic polar and nonpolar regions Functions include energy storage membrane structure or specific biological functions such as signal transmission gt gt Building blocks of several classes of lipids Long amphipathic unbranched hydrocarbon chain with a carboxyl group at one end I Carboxyl polar group is head I Nonpolar hydrocarbon chain is quottailquot gt Hydrocarbon tails are variable in length but usually 1220 carbons long gt Highly reduced and yield a large amount of energy upon oxidation I Each carbon atom in chain is bonded to maximum number of hydrogens 0 Long straight chains that pack together well I Have one or more double bonds 0 Bends in chains and less tight packing gt Type of unsaturated fatty acids with a particular type of double bond that causes less of a bend in the chain gt Relatively rare in nature and are produced artificially in shortening and margarine gt Linked to increased risk of heart disease and elevated cholesterol levels gt Consist of glycerol molecule with 3 fatty acid chains gt Energy storage gt Mostly saturated fats I Solid semisolid at room temperature and are called fats o In plants liquid at room temperature and are predominately unsaturated gt Important to membrane structure due to amphipathic nature gt Important to membrane structure I Predominant phospholipids in most membranes I Phosphatidic acid 0 Basic components 0 2 fatty acids and a phosphate group gt Small hydrophilic alcohol head I Serine ethanolamine choline inositol 0 Charged gt Specialized membrane components gt Contain carbohydrates I One to six sugar unites attached gt Occur largely on outer monolayer of plasma membrane gt Derivatives of 4ringed hydrocarbon skeleton gt Relatively nonpolar hydrophobic gt Cholesterol in animal cells Chapter 7 membranes gt Define boundaries of cells and organelles and act as permeability barriers gt Serve as sites for biological functions such as electron transport gt Possesses transport proteins that regulate the movement of substances into and out of cells and organelles gt Contain protein molecules that act as receptors to detect external signals gt Provide mechanisms for celltocell contact adhesion and communication gt Fluid mosaic model o Fluid lipid bilayer o Mosaic of proteins embedded in bilayer I Localized regions or membrane lipids I Regions sequester proteins involved in cell signaling I Dynamic structures Integral membrane proteins Peripheral proteins Lipidanchored proteins Lipids are in constant motion Phospholipids are most abundant in membrane I Include phosphoglycerides and sphingolipids Kinds relative proportions of phospholipids vary greatly among types of membranes VVVVV V gt Formed by addition of carbohydrates gt Cholesterol in animal cell membranes I Stabilize maintain membrane gt All membrane lipids gt Long hydrocarbon tails provide barrier to diffusion of polar solutes gt 68nm thick membrane gt Mobile in monolayer gt Rotation gt Lateral diffusion I Transverse diffusion is rare 0 Flippases gt Measures by