230 likes | 398 Views
Energy and Metabolism. Chapter 8. Outline. Flow of Energy in Living Things Laws of Thermodynamics Free Energy Activation Energy Enzymes Forms Activity ATP Biochemical Pathways. Flow of Energy in Living Things. Energy - the capacity to do work kinetic - energy of motion
E N D
Energy and Metabolism Chapter 8
Outline • Flow of Energy in Living Things • Laws of Thermodynamics • Free Energy • Activation Energy • Enzymes • Forms • Activity • ATP • Biochemical Pathways
Flow of Energy in Living Things • Energy - the capacity to do work • kinetic - energy of motion • potential - stored energy • Thermodynamics - changes in heat • calorie - heat required to raise the temperature of one gram of water one degree Celsius • kilocalorie = 1000 calories
Flow of Energy in Living Things • Oxidation - Reduction • Oxidation occurs when an atom or molecule loses an electron. • Reduction occurs when an atom or molecule gains an electron. • Redox reactions occur because every electron that is lost by an atom through oxidation is gained by some other atom through reduction.
Laws of Thermodynamics • First Law of Thermodynamics • Energy cannot be created or destroyed, but only change form. • During each conversion, some of the energy dissipates into the environment as heat. • Heat is defined as the measure of the random motion of molecules.
Laws of Thermodynamics • Second Law of Thermodynamics • The disorder (entropy) in the universe is continuously increasing. • Energy transformations proceed spontaneously to convert matter from a more ordered, less stable form, to a less ordered, more stable form.
Free Energy • Free energy refers to the amount of energy actually available to break and subsequently form other chemical bonds. • Gibbs’ free energy (G) • change in free energy • endergonic - any reaction that requires an input of energy • exergonic - any reaction that releases free energy
Activation Energy • Activation energy refers to the extra energy required to destabilize existing chemical bonds and initiate a chemical reaction. • catalyst - substance that lowers the activation energy • cannot violate laws of thermodynamics. • direction of a chemical reaction is determined solely by the difference in free energy between the reactants and the products
Enzymes Are Biological Catalysts • Enzymes are proteins that carry out most catalysis in living organisms. • Unique three-dimensional shape enables an enzyme to stabilize a temporary association between substrates. • Because the enzyme itself is not changed or consumed in the reaction, only a small amount is needed, and can then be reused.
Enzymes • Most enzymes are globular proteins with one or more active sites. • Substrates bind to the enzyme at these active sites, forming an enzyme-substrate complex.
Enzyme Forms • A multienzyme complex is composed of several enzymes, catalyzing the different steps of a sequence of reactions, that are associated with one another. • subunits work in concert, providing significant advantages in catalytic efficiency • RNA catalysts “ribozymes”
Factors Affecting Enzyme Activity • Temperature • Rate of an enzyme-catalyzed reaction increases with temperature, but only up to an optimum temperature. • pH • Ionic interactions also hold enzymes together.
Factors Affecting Enzyme Activity • Inhibitors and activators • inhibitor - substance that binds to an enzyme and decreases its activity • competitive inhibitors - compete with the substrate for the same active site • noncompetitive inhibitors - bind to the enzyme in a location other than the active site • allosteric sites - specific binding sites acting as on/off switches
Factors Affecting Enzyme Activity • activator - substances that bind to allosteric sites and keep the enzymes in their active configurations • increase enzyme activity • cofactors - chemical components that facilitate enzyme activity • coenzyme
ATP • Adenosine triphosphate (ATP) is the chief energy currency of the cell. • Each molecule is a nucleotide composed of ribose, adenine, and a triphosphate group. • energy stored in the triphosphate group • cell uses ATP to drive endergonic reactions
Biochemical Pathways • Biochemical pathways are the organizational units of metabolism. • Metabolism is the total of all chemical reactions carried out by an organism. • anabolism - reactions that expend energy • catabolism - reactions that harvest energy
Regulation of Biochemical Pathways • Biochemical pathways must be coordinated and regulated to operate efficiently. • advantageous for cell to temporarily shut down biochemical pathways when their products are not needed • feedback inhibition - When the cell produces increasing quantities of a particular product, it automatically inhibits its ability to produce more.
Summary • Flow of Energy in Living Things • Laws of Thermodynamics • Free Energy • Activation Energy • Enzymes • Forms • Activity • ATP • Biochemical Pathways