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MU BIO 116 - Enzymes

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Biology 116 1st Edition Lecture 8Outline of Last Lecture I. Cell communication typesII. Two ways for cells to communicateOutline of Current Lecture I. Laws of Thermodynamics II. EnergyIII. Free EnergyIV. Enzymesa. Inhibition (2 types)Current LectureLaws of Thermodynamics Everything obeys the these two laws1) energy cannot be created or destroyed 2) changing forms of energy always creates more entropy (or more disorder)Energy- the capacity to do workKinetic- moving thingsPotential- stored energyElectrical- moving electronsThermal- hot objects Chemical- bonds between atoms Light- electromagnetic radiationFree Energy- the amount of energy available to DO WORK as a result of an energy transformation, always <100%These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Ex) If there are a million calories in a log, when the log burns some of those calories will be lost to entropy and cannot do work There are two types:Exergonic (Spontaneous)- Energy is released, free energy is negativeEndergonic- Energy is required, free energy is positiveExergonic reactions can drive endergonic reactions Enzymes- biological catalysts that facilitate biochemical reactions -Amino acids make proteins which make enzymes Ribozymes- (not talked about for the rest of the lecture) RNA molecules that act as catalysts Catalysts- increase the probability of a reaction Major features of enzymes:-Are not consumed during a reaction-The reactions were going to occur anyways -They create new pathways for the reactions, same beginning and ending point Ex) A cop tells a robber to get on his knees and he does it willingly (no enzyme) OR A coptells a robber to get on his knees and the robber refuses so the cop uses force (with enzyme).-Enzyme catalyzed reactions can go both ways (the probability of it going one way is common, but it can possibly go the other way too)-Reduce the Activation Energy (minimum amount of energy required to make a reaction happen) and increase the probability that the reaction will occur-Allow molecules to get close enough to cause bond rearrangement -Allows the enzyme to grab the substrateEnzyme Features -Active site: “business end” of the enzyme where reaction happens -Substrate: what the enzyme binds to-Enzyme-Substrate complex: when the enzyme and substrate combine -Products: resulting molecules after the enzymeAn enzyme is not a fixed molecule, it changes its shape after the substrate is bound, and then changes it again in order to release it and pick up a new one.An enzyme has a 3D shape that fits with a substrate.Enzymes are generally extremely specific- always only do one certain jobThink of the enzyme as a catcher’s mitt that closes once the substrate enters and then opens back up afterwards, the substrate has a very different shape afterwards.-Biochemists test enzymes by controlling the number of enzymes and substrates and observing the speed at which the reactions take place-Low concentrations of substrates = low probability of the an enzyme running into a substrate-More substrate = more probably enzyme substrate -Can get to the point where there are so many substrates that you reach the substrate limiting rate-This rate is where the plot levels out and the maximal velocity (Vmax) occursHalf of the Vmax is the Km which shows how well the enzyme works -Lower Km: better enzyme, increasing probability of reaction going forward -Higher Km: weaker enzyme, decreased probability of reaction going forwardInhibition (2 types)Competitive:Analog molecules (molecules that looks very similar to the substrate) compete with the substrate for active site. Means there is more substrates needed to complete the reaction at thesame rate. Km increase. Noncompetitive:Non-analog binds to the other sites of the enzyme and affects the rate of reaction without actually affecting the enzymes ability to bind with the substrate. Lowers Vmax without affecting Km.Other requirements for enzymesProsthetic groups- small molecules that are permanently attaches to the enzyme (some actuallyhelp the enzyme)Cofactor- inorganic ion that lightly/ temporarily binds to the enzyme Coenzyme- organic molecules bond covalently and that participates in reaction but left unchanged after Greatly affected by temperature and pH, outside of a certain range they do not work as


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MU BIO 116 - Enzymes

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