Chapter 6 - BSC 1010 Dr. Presley Chapter 6 ENERGY, ENZYMES,...

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BSC 1010 Dr. Presley Chapter 6 ENERGY, ENZYMES, and METABOLISM ENERGY = capacity to do work (physics definition) - capacity for change (biochemical interpretation) - cells require energy from its environment - energy can neither be created nor destroyed, but can be transformed (1 st Law) - in biology, energy transformations involve molecular movement and changes in chemical bonding - classification of energy: –Kinetic energy = energy of motion (energy in action) ex.: water rushing through a dam and turning the turbines, types: mechanical, light, electrical, heat –Potential energy = energy due to location or structure, “stored energy” example: water behind a dam, electrons in the outer energy shell types: chemical bonds, electrical potential, concentration gradients METABOLISM - sum total of the chemical conversions occurring in a cell. -Types: - Catabolism - degradative pathways - breaking complex molecules - reactions release energy (exergonic) Study Fig 6.3 a, p. 110 often this energy will be used to drive anabolic reactions (coupled reactions) - ex.: hydrolysis of macromolecules during digestion, aerobic cellular respiration, beta-oxidation of lipids - Anabolism - synthetic reactions - linking smaller molecules together to form complex molecules - require energy (endergonic) Study Fig 6.3 b, p. 110 - therefore this energy is stored in the chemical bonds of these larger molecules - ex.: dehydration synthesis reactions for production of proteins, polysaccharides, fats, phospholipids - Metabolic Pathway: a series of reactions where the product(s) of one enzymatically- controlled reaction becomes the reactants of the next enzymatic step. The result is the end product. The pathway is stopped if and reactant or enzyme is missing. Enzyme 1 Enzyme 2 Enzyme 3 A --------------> B --------------> C ---------------> D (text p. 119) - Think: Degradative pathways (catabolic) drive synthetic pathways (anabolic). THERMODYNAMICS - the study of energy transformations occurring in matter - systems of study: closed = isolated, self-contained, energy does not leave, energy does not enter, the laws of thermodynamics are based on a closed system open = matter and energy are exchanged with their surroundings, as humans we are an open system, our Earth is an open system FIRST LAW OF THERMODYNAMICS Study Fig. 6.2a, p.108 - “law of conservation of energy” - energy is neither created nor destroyed, but can be converted from one form to another - the amount of energy at the start will equal the total energy at the end - ex. light energy is converted chemical energy (food) by green plant plus heat SECOND LAW OF THERMODYNAMICS Study Fig. 6.2b, p.108 - when energy is transformed, some energy is unavailable to do work - total energy in a biological system is referred to as enthalpy (H) - usable energy is referred to as free energy (G) - unusable energy is referred to as entropy (S), is a measure of disorder in system - H = G + TS ; where T is absolute temperature - ∆G = ∆H - T∆S This equation allows us to calculate the change in free energy. If ∆G is negative, free energy is released (catabolic, exergonic)
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Chapter 6 - BSC 1010 Dr. Presley Chapter 6 ENERGY, ENZYMES,...

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