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Bio Exam 2 notes

Bio Exam 2 notes - E nergy and Metabolism I B iological...

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Energy and Metabolism I. Biological work requires energy A. Energy is the capacity to do work B. Energy is expressed in units of work (kilojoules) or heat energy (kilocalories) C. Organisms carry out conversions between potential energy and kinetic energy I I. Two laws of thermodynamics govern energy transformations A. The total energy in the universe does not change B. The entropy of the universe is increasing I I I. Metabolic reactions involve energy transformations A. Metabolism of an organism includes anabolic and catabolic pathways B. Enthalpy is the total potential energy of a system C. Free energy is energy that is available to do cellular work, and hence is of biological interest D. Chemical reactions involve changes in free energy 1. The Greek letter delta (D) is used to refer to changes between initial and final states 2. DG = DH – TDS E. Free energy decreases during an exergonic reaction 1. The total free energy of a system in the final state is less than the total free energy in the original state 2. Exergonic reactions have a –DG F. Free energy increases during an endergonic reaction G. Free energy changes depend on the concentrations of reactants and products H. Cells drive endergonic reactions by coupling them to exergonic reactions IV. Adenosine triphosphate (ATP) is the energy currency of the cell A. The ATP molecule has three main parts B. ATP donates energy through the transfer of a phosphate group C. ATP links exergonic and endergonic reactions
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D. The cell maintains a very high ratio of ATP to ADP V. Cells transfer energy by redox reactions A. Oxidation is the loss of electrons; reduction is the gain of electrons 1. Oxidation involves the loss of energy; reduction is the gain of energy 2. These processes occur simultaneously, called redox reactions B. Most electron carriers carry hydrogen atoms VI. Enzymes are chemical regulators A. Nearly all enzymes are protein catalysts that speed the rate of chemical reactions 1. Not all organic catalysts are enzymes; some nucleotide-based molecules function as enzymes as well B. All reactions have a required energy of activation (EA) C. An enzyme lowers the activation energy needed to initiate a chemical reaction 1. Enzymatic action has no effect on the overall free energy D. An enzyme works by forming an enzyme-substrate (ES) complex E. Most enzyme names end in -ase 1. Sucrase is an enzyme that reacts with sucrose 2. Other enzymes have older names ending in –zyme 3. Enzyme names such as pepsin and trypsin give no clues as to their function F. Enzymes are specific 1. Because of the binding at the active site, the substrate is very specific to the enzyme 2. Not all enzymes are specific (e.g. lipases react with a variety of fats) G. Many enzymes require cofactors 1. Most vitamins are coenzymes or are parts of coenzymes
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Bio Exam 2 notes - E nergy and Metabolism I B iological...

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