Chapter 8 An Introduction to Metabolism

Chapter 8 An Introduction to Metabolism - Chapter 8 An...

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Chapter 8 An Introduction to Metabolism 8.1 Metabolism : the totality of an organisms chemical reactions Metabolic pathway : is one that begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product. Each step of the pathway is catalyzed by a specific enzyme. Catabolic pathways : pathways that release energy by breaking down complex molecules to simpler compounds. Ex: cellular respiration Anabolic pathways : consume energy to build complicated molecules from simpler ones ex: synthesis of protein from AA. Bioenergetics : study of how energy flows through living organisms. Energy : capacity to cause change. o Kinetic energy : energy associated with the relative motion of objects ex: heat or light o Potential energy : energy matter possesses because of its location or structure such as chemical energy, which is a term used by biologists to refer to PE available for release in chemical rxn. Thermodynamics : the study of the energy transformations that occur in a collection of matter. 1 st law of thermodynamics : energy in the universe is constant. Energy can be transferred and transformed but it cannot be destroyed or created. 2 nd law of thermodynamics : every energy transfer or transformation increases the entropy (measure of randomness) of the universe. Spontaneous : process that can occur without an input of energy For a process to occur spontaneously, it must increase the entropy of the universe. 8.2 Free energy : is the portion of a systems energy that can perform work when temperature and pressure are uniform throughout the system. G= H - T S. H is the change in systems enthalpy. S is the change in systems entropy. • ∆ G = Gfinal – Ginitial Exergonic reactions : one that proceeds with a net release of free energy. G is negative. Endergonic reaction : one that absorbs free energy from surrounding and so G is positive. 8.3 A cell does 3 main kinds of work o Chemical work: the pushing of endergonic reactions. o Transport Work: the pumping of substances across membranes against the direction of spontaneous movement. o Mechanical Work: things like beating of the cilia and contraction of the muscle cells. Energy coupling: the use of an exergonic process to drive an endergonic one. ATP: is adenosine triphosphate which is a sugar ribrose with a nitrogenous base adenine and a chain of 3 phosphate groups bonded to it. One of the nucleoside triphosphates that make RNA. Bonds between phosphate groups of ATP can be broken by hydrolysis. It releases 7.3 kcal/mol. ATP is important because the energy it releases on losing a phosphate group is somewhat greater than the energy
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Chapter 8 An Introduction to Metabolism - Chapter 8 An...

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