Chapter 08 - Chapter 08 An Introduction to Metabolism...

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Chapter 08 - An Introduction to Metabolism Chapter 8 An Introduction to Metabolism Lecture Outline Overview: The Energy of Life Concept 8.1 An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics The totality of an organism’s chemical reactions is called metabolism. Metabolism is an emergent property of life that arises from interactions between molecules within the orderly environment of the cell. The chemistry of life is organized into metabolic pathways. Metabolic pathways begin with a specific molecule, which is then altered in a series of defined steps to form a specific product. A specific enzyme catalyzes each step of the pathway. Catabolic pathways release energy by breaking down complex molecules to simpler compounds. o A major pathway of catabolism is cellular respiration, in which the sugar glucose is broken down in the presence of oxygen to carbon dioxide and water. Anabolic pathways consume energy to build complicated molecules from simpler compounds. They are also called biosynthetic pathways. o The synthesis of protein from amino acids is an example of anabolism. The energy released by catabolic pathways can be stored and then used to drive anabolic pathways. Energy is fundamental to all metabolic processes, and therefore an understanding of energy is key to understanding how the living cell works. o Bioenergetics is the study of how organisms manage their energy resources. Organisms transform energy. Energy is the capacity to do work. o Energy exists in various forms, and cells transform energy from one type into another. Kinetic energy is the energy associated with the relative motion of objects. o Objects in motion can perform work by imparting motion to other matter. o Photons of light can be captured and their energy harnessed to power photosynthesis in green plants. o Heat or thermal energy is kinetic energy associated with the random movement of atoms or molecules. Potential energy is the energy that matter possesses because of its location or structure.
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o Chemical energy is a form of potential energy stored in molecules because of the arrangement of their atoms. Energy can be converted from one form to another. o For example, as a boy climbs stairs to a diving platform, he is releasing chemical energy stored in his cells from the food he ate for lunch. o The kinetic energy of his muscle movement is converted into potential energy as he climbs higher. o As he dives, the potential energy is converted back to kinetic energy. o Kinetic energy is transferred to the water as he enters it. o Some energy is converted to heat due to friction. The energy transformations of life are subject to two laws of thermodynamics. Thermodynamics is the study of energy transformations.
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Chapter 08 - Chapter 08 An Introduction to Metabolism...

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