Chapter 8- Metabolism

Chapter 8- Metabolism - 1/21/2010 Metabolism 2010: D....

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1/21/2010 1 Metabolism © 2010: D. Julian Metabolism Metabolism is the totality of an organism’s chemical reactions. Metabolism is an emergent property of life that arises from interactions between molecules within the cell. An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics . Bioenergetics is the study of how organisms manage their energy resources. © 2010: D. Julian Metabolic pathways Chemical reactions are organized into metabolic pathways. A pathway begins with a specific molecule that is then altered in a series of steps (e.g., by cleavage, oxidation, reduction, phosphorylation), ultimately forming a certain product. Typically, each step is catalyzed by a specific enzyme. © 2010: D. Julian Enzyme 1 Enzyme 2 Enzyme 3 D C B A Reaction 1 Reaction 3 Reaction 2 Starting molecule Product
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1/21/2010 2 Catabolic vs. anabolic metabolism Catabolic pathways : Metabolic pathways that release energy (e.g., cellular respiration). Anabolic pathways : Metabolic pathways that consume energy (used to build complicated molecules from simpler ones). © 2010: D. Julian Thermodynamics © 2010: D. Julian Forms of energy Energy : Capacity to cause change. Kinetic energy : Energy associated with relative motion of objects (including atoms and molecules). Heat ( thermal energy ) : Kinetic energy associated with random movement of atoms and molecules. Potential energy : Energy due to location or structure. Chemical energy : Potential energy available for release in a chemical reaction. © 2010: D. Julian
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1/21/2010 3 Open vs. closed systems A closed system , such as that approximated by liquid in a thermos, is isolated from its surroundings. In an open system , energy and matter can be transferred between the system and its surroundings. Organisms are open systems. © 2010: D. Julian First law of thermodynamics The energy of the universe is constant . Energy can be transferred and transformed, but it cannot be created or destroyed . Also known as the principle of conservation of energy . © 2010: D. Julian (a) First law of thermodynamics (b) Second law of thermodynamics Chemical energy Heat CO 2 H 2 O + Second law of thermodynamics Energy transfer or transformation increases the entropy (randomness or disorder) of the universe . If a process occurs spontaneously, it must increase the entropy of the universe. © 2010: D. Julian (a) First law of thermodynamics (b) Second law of thermodynamics Chemical energy Heat CO 2 H 2 O +
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1/21/2010 4 Biological order and disorder Energy flows into an ecosystem in the form of light and exits in the form of heat. Cells can create ordered structures from less ordered materials (i.e., cells can locally decrease entropy), all living systems increase the entropy of the universe. © 2010: D. Julian 50 μm More free energy (higher G ) Free energy A living system’s free energy ( G ) is energy that can do work when temperature and pressure are uniform, as in a living cell.
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Chapter 8- Metabolism - 1/21/2010 Metabolism 2010: D....

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