` Bios 208 1st Edition Lecture 13 Outline of Last Lecture I. Energy changes in exergonic and endergonic reactionsII. Equilibrium and MetabolismIII. The Structure and Hydrolysis of ATPOutline of Current Lecture I. Activation energyII. EnzymesIII. Early MicroscopyCurrent LectureI. Activation energyA. Activation energy of a reaction is like pushing a car over a hilltop. You need to put some initial energy in to get the reaction to a point where it will go on its own.B. ∆G (exergonic; products are > stable than reactants; stability is related to their enthalpies and therefore is unchangeable)C. Old bonds must be broken, which requires E Activation Energy (EA) “barrier” must be overcomeD. Energy is released as new bonds form to make products.E. Catalysts lower the activation energy of a reaction. ∆ G is not affected by the catalyst.F. A small decrease in EA (50%) can have a great effect on reaction rate (increase 1000x).G. Reactions happen because of molecular collisions. Activation energy helps more molecules collide. Energy input can break bonds, forming new bonds gives Energy output.H. Chain reactions occur where E release from some molecules provides activation E for therest…EXPLOSIVE!II. EnzymesA. Enzymes are biological catalysts.B. Substrates bind to an enzyme’s active site.C. Upon binding, the shape of the enzyme and its active site change “induced fit”.D. The transition state occurs here; this is where old bonds are broken and new bonds are made.E. Free enzyme, free substrates.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.F. Substrates bind to the active site (“lock-in-key fit”).G. Bonds are strained, and then broken at the transition state, which requires E. EA is lowerwith an enzyme than without.H. New bonds form to make the products.I. Products are released.J. The enzyme is unchanged. Repeat steps 1-5 K. Temperature (top): human enzymes vs. heat-tolerantL. Bacteria pH (bottom): human stomach vs. intestinal enzymesM. Co-factors assist enzymesa) Inorganic co-factors: e.g., ions such as Fe in hemoglobinb) Co-enzymes are organic cofactors (i.e., they contain carbon; e.g., NADH)N. Enzyme activity can be reduced by cellular inhibitors.a) Competitive inhibitors bind to the active site of an enzyme, which prevents the substrate from bindingb) Non-competitive inhibitors bind to an allosteric site (i.e., not the active site). Structure of active site is changed, so substrate no longer can bind.O. Allosteric regulators. An enzyme can have active and inactive forms.a) Activators hold the enzyme in an active form and increase enzyme activityb) Inhibitors hold the enzyme in an inactive form and decrease enzyme activityP. Feedback inhibition of an enzymatic pathwayQ. Isoleucine (Ile) biosynthesis: anabolic pathway with 5 enzymatic steps.R. Product of the first reaction is the substrate for the second reaction.S. Final product (Ile) is the allosteric inhibitor of the first enzyme (rxn.#1).T. High [Ile] low activityU. Low [Ile] high activity; “turn on “enzymes and make more IleIII. Early MicroscopyA. Understanding cell biology had to await the development of light microscopesB. Robert Hooke built one of the first microscopes and Wrote Micrographia (1665).C. He observed many structures with a simple microscope.D. Cork (from bark of an oak tree) contains “little rooms” or CELLS.E. Hooke also observed a flea in great detail.F. Robert Hooke Microscope
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