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Lecture 4 - Lecture 4 Another role for proteins is acting...

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Lecture 4 Another role for proteins is acting as enzymes. Energy, Enzymes, and Metabolism There are a lot of metabolic pathways – different enzymes catalyze the different reactions in each pathway. Catalysis occurs due to the 3-D shape of the enzyme. The shape of the protein is really important in its role and function. The enzyme has to have a certain shape that matches with the substrates that it is going to be catalyzing the reaction for. If you change the protein shape, it’s not going to be able to match up with certain substrates. Metabolism – the sum of all these reactions. Chemical Reactions of Metabolism Anabolic – building something up o Building a molecule – monomers together to build a polymer. o Condensation reaction Catabolic – breaking something down. o Polymer broken down to monomers. Energy and the Laws of Thermodynamics Bioenergetics – the flow of energy in the system. Energy – the capacity to do work (the usable energy) i.e. moving ions against the gradient different cellular types of movement – kinesin, dynein all these require energy to be able to do that type of work. Forms of energy – Heat o not something that the cell is able to harness o Anything lost as heat, we can’t actually use that energy to do anything with it. Light (photosynthesis) Electrical and chemical energy. Categories of Energy Kinetic – energy of motion, the flow of electrons o Electron flow from one substance to another. o Used to pump out protons during cellular respiration. Potential – store in chemical bonds or concentration gradients. o i.e. when sodium moves down its gradient, there is potential energy that was stored in that gradient. Laws of Thermodynamics Total energy is always going to be constant. o In a chemical reaction, you’re never adding energy or taking away total energy. o The same energy you started out with will be the same amount of total energy at the end. o Nothing’s created or lost through the different transformations. Quality of energy.
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Lecture 4 Quality of energy changes from reaction to reaction, but total amount doesn’t change. The amount of usable energy as you undergo a reaction gets less. You get less usable energy after a reaction. Energy and the Laws of Thermodynamics First Law of Thermodynamics o Energy is neither created nor destroyed. Second Law of Thermodynamics o When energy is converted from one form to another, some of that energy becomes unavailable to do work. o Just the quality is changing; basically your entropy (unusable energy) is increasing as you go from transformation to transformation. Disorder is always increasing (amount of unusable energy you have is increasing).
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