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Energy and Metabolism. Energy Capacity to do work, which is any change in the state or motion of matter Measured as heat energy Unit of measure is the kilocalorie (kcal). Potential energy Capacity to do work owing to position or state
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Energy • Capacity to do work, which is any change in the state or motion of matter • Measured as heat energy • Unit of measure is the kilocalorie (kcal)
Potential energy • Capacity to do work owing to position or state • Chemical energy is potential energy stored in chemical bonds • Kinetic energy • Energy of motion
Closed system does not exchange energy with its surroundings • Organisms are open systems
First law of Thermodynamics • Energy cannot be created or destroyed • Energy can be transferred and changed in form • Organisms cannot produce energy, but as open systems, they can capture it
Second law of Thermodynamics • Entropy is continuously increasing • No energy transfer is 100% efficient • Some energy is dissipated as heat • Organisms maintain their organization only with input of energy from surroundings
Metabolism • Sum of all the chemical activities taking place in an organism • Anabolism • Complex molecules synthesized from simpler substances • Catabolism • Larger molecules broken down into smaller ones
Enthalpy is total potential energy of a system • As entropy increases, amount of free energy decreases • H = G + TS • H is enthalpy • G is free energy • S is entropy • T is absolute temperature in degrees Kelvin
Exergonic reaction • Releases energy that can perform work • In coupled reaction, supplies input of free energy to drive an endergonic reaction • Endergonic reaction increases free energy
Dynamic equilibrium • In a chemical reaction, rate of change in one direction is the same as in the opposite direction • When concentration of reactant molecules increases, the reaction shifts until equilibrium is re-established
Adenosine triphosphate (ATP) • Holds readily available energy for very short periods • Donates energy by means of terminal phosphate group • Common link between • Exergonic and endergonic reactions • Catabolism and anabolism
ATP linksexergonicand endergonic reactions
Redox reactions • Substance that becomes oxidized gives up energy • Substance that becomes reduced receives energy • Essential part of cellular respiration, photosynthesis, and other chemical reactions
Enzymes • Biological catalysts • Cells regulate the rate of chemical reactions with enzymes • Lower activation energy (energy required to break existing bonds) • Although most enzymes are proteins, some types of RNA molecules have catalytic activity as well
Enzymes • Work best at specific temperature and pH conditions • Catalyze virtually every chemical reaction that takes place in an organism • Some enzymes consist only of protein • Some enzymes have two components • Protein called apoenzyme • Cofactor
Important classes of enzymes [insert table 6-1 when available]
Feedback inhibition • Formation of an end product inhibits an earlier reaction in the metabolic pathway
Reversible inhibition • Competitive inhibition • Inhibitor competes for the substrate for the active site • Noncompetitive inhibition • Inhibitor binds with enzyme at a site other than active site • Irreversible inhibition • Inhibitor combines with an enzyme and permanently inactivates it