BIOLOGY 111 1st Edition Lecture 10 Outline of Last Lecture I. Osmosis II. Tonicity III. OsmoregulationIV. MetabolismV. Gibbs Free EnergyOutline of Current Lecture I. EquilibriumA. Open vs Closed systemsB. Exergonic reactions and Endogonic reactionsII. ATPIII. Catalyst A. Enzyme and RibozymesB. Activation Energy and Transition StateIV. EnzymesA. PurposeB. Active Site and Induced FitC. Environment factorsV. Inhibitors A. Competitive vs Noncompetitive inhibitorB. Feedback inhibitor 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.Current LectureEquilibrium- Closed systems will reach equilibrium (∆G=0). And once the system reaches equilibrium, the reaction will usually stop and not continue to function. - Open systems will never reach equilibrium (∆G ≠ 0) because there is a continuous flow ofenergy. The reactants and products cycle continuously. - An example of this would be cells because they experience a constant flow of materials. In cells, processes with very large negative ∆G’s are usually broken down in smaller steps where energy can be captured in manageable chunks.- Metabolism is also something that is never at equilibriumExergonic reaction – net release of free energy (∆G < 0)- energy moves outward - occurs spontaneously (-∆G)- reactants > products- don’t require workEndergonic reaction – absorbs (stores) free energy from its surroundings (∆G > 0)- energy moves inward- does not occur spontaneously (+∆G)- reactants < products- require work- Cells do three main kinds of work:1. Chemical work – pushing of endergonic reactions (don’t occur spontaneously)2. Transport work – pumping substances across membranes against the direction of spontaneous movement3. Mechanical work (i.e. movement by cilia(or flagella), contraction of muscle cells…)energy coupling – use of an exergonic process to drive an endergonic one (ATP is responsible formediating most energy coupling in cells and is also usually the immediate source of energy)*the key to coupling exergonic and endergonic reactions is the formation of a phosphorylated intermediate that is more reactive (less stable) than an unphosphorylated moleculePhosphorylated intermediate – the molecule receiving the phosphate group from the ATP and iscovalently bonded (explained next)Phosphorylation – phosphate directly transferred to glucose ATP (adenosine triphosphate)- contains sugar ribose, nitrogenous base adenine and a chain of three phosphate groups- mediates energy coupling - main source of energy- hydrolysis breaks the bonds between the phosphate groups and adds water to the terminal phosphate bond, creating ADP (adenosine diphosphate)- [ATP + water] ---------(hydrolysis)-------- [ADP + phosphate] - Hydrolysis of last phosphate on ATP, ∆G = -7.3 kcal/mol- The energy ATP releases on losing a phosphate group is somewhat greater than energy most other molecules could deliverCatalyst – agent that speeds up the rate of a chemical reaction without being consumed during the reaction- Enzymes – most common protein catalysts in living cells - Ribozymes – RNA molecules with catalytic properties *enzymes are more common than ribozymes as catalystsActivation Energy (EA) – the energy required to start a reaction and get it to the transition state, this is often supplied in the form of heat from the surroundingsTransition State – when molecules have absorbed enough energy for the bonds to break, making the reactants be in their most unstable condition Enzymes- Speed up reactions by lower the activation energy barrier (these do not affect the ∆G or equilibrium)- Channels the reaction in certain directions (most are reversible, catalyzing forward or backwards, depending on which direction has negative ∆G)- Allow the cell to control the reactions- Bind to substrates- Active Site – pocket or a groove on the surface of an enzyme where catalysis occurs, capable of lowering EA and speed up a reaction by:1. Orienting substrates correctly2. Bonding the substrate3. Providing a favorable microenvironment- Induced fit – brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction (the enzyme actually changes shape so that the active sit can enfold the substrate) - Affected by environmental factors (some enzymes work better under certain circumstances than others, because these optimal conditions favor the most active shape for enzyme molecules)- Temperature – the rate of enzymatic reaction increases with increasing temperature because substrates collide with active sites more frequently when molecules move more rapidly. Above that temperature, however, the speed of the enzymatic reaction drops sharply because it denatures. - pH – the optimal most enzymes fall in the range of pH 6-8 (pepsin-stomach enzyme prefers pH 2 and trypsin-intestinal enzyme prefers pH 8)Cofactor – non-protein enzyme helper that is usually an inorganic ion that permanently binds tothe enzyme or temporarily binds to the substrateCoenzyme – an organic cofactor that participate in a reaction and remain unchanged afterwardsProsthetic Groups – small molecules permanently attached to the enzyme and help catalyzeInhibitors - Competitor inhibitor – reduce the productivity of enzymes by blocking substrates from entering active sites. They fight for the active site. If increase the concentration of a substrate, there will be less competitive inhibition. If you decrease the concentration of a substrate, there will be more competitive inhibition. Examples include:- Toxins- Poisons - Pesticides- Antibiotics- Noncompetitive inhibitor – do not directly compete with the substrate to bind to the enzyme at the active site. Will bind to the allosteric site and alter the structure of the enzyme so it cannot carry out the reaction. The concentration of substrate does not matter like in a competitive inhibitor.- Feedback inhibition – the end product of a metabolic pathway allosterically inhibits the enzyme for a previous step in the