Reading Guide: Biology Energy and Metabolism 8.1 The laws of thermodynamics describe how energy changes. The Flow of Energy in Living Things • Energy is ________________, ____________ energy is energy of motion, while ________________ is stored energy. • ______________ is the process whereby an atom or molecule loses an electron, and -------- is the process whereby an atom or molecule gains an electron. Oxidation-reduction reactions always take place together. The Laws of Thermodynamics • The First Law of Thermodynamics states that energy cannot be created or destroyed; it can only change from one form to another. • During each energy conversion, some energy dissipates into the environment as _____ • The Second Law of Thermodynamics states that disorder (__________) in the universe is continuously increasing. • Entropy is always increasing because, as more energy is used, more energy is converted to heat. Free Energy • The amount of energy available to break and form chemical bonds is referred to as a molecule's free energy • Reactions in which the products contain less free energy than the reactants ___________________________ Activation Energy • ______________is the extra energy required to destabilize existing chemical bonds • _______________increase the rate of reaction by_________________ but do not alter the proportions of the _________________ 8.2 Enzymes are biological catalysts. Enzymes • Cells use _____________ to lower activation energies. _______________ enzymes are known, each catalyzing one or a few specific chemical reactions How Enzymes Work • Most enzymes are ____________ with one or more __________ where specific substrates can bind, forming an _________________________. Enzymes Take Many Forms • Multienzyme complexes are noncovalently bonded assemblies of enzymes that catalyze different steps of a reaction sequence, and can offer significant advantages in catalytic efficiency. • Not all biological catalysts are proteins; for example, certain reactions can be catalyzed by ribosomes Factors Affecting Enzyme Activity • Several factors can affect the activity of an enzyme, including ______________________________________________________. 8.3 ATP is the energy currency of life. • The chief energy currency all cells use is a molecule called __________. • Because of electrostatic repulsion, the covalent bonds between phosphates are unstable; thus, ATP is an excellent energy donor. 8.4 Metabolism is the chemical life of a cell. Biochemical Pathways: The Organizational Units of Metabolism • _________________ refers to the total of all chemical reactions carried out by an organism. • Biochemical pathways occur when the _____________________ for the next reaction. • To operate efficiently, a biochemical pathway must be coordinated and regulated by the cell, and regulation often takes place as _________________.