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Unformatted text preview: EAS 1600 Introduction to Environmental Sciences ____________________________ Class 26 - The Biosphere: Part 2 Metabolic Processes Evolution of Biosphere and Earth System ________________________________ In this lecture we discuss the various chemical pathways or strategies organisms use to survive, and the role these pathways play in the Earth System. Whats a metabolic process? And why are they necessary? Organisms are in a thermodynamic bind: They represent highly-ordered systems of complex molecules. But the 2 nd Law of Thermodynamics states that Ordered systems will tend to spontaneously disperse To survive despite 2 nd Law, organisms must constantly expend energy to: synthesize new living material (protoplasm) anabolism (discussed below) carry out necessary maintenance activities catabolism (discussed below) But the 1 st Law of Thermodynamics states that Energy is conserved, so To survive, organisms must gather and use energy Metabolic processes describe the manner in which various organisms gather and use energy to survive. Before we look at these metabolic processes in detail, we need to consider two related issues: (i) the chemical nature of metabolic processes; and (ii) the classification of organisms. CHEMICAL NATURE OF METABOLIC PROCESSES Excerpted from: http://textbookofbacteriology.net/metabolism.html ...metabolism refers to the sum of the biochemical reactions required for energy generation and the use of energy to synthesize cell material from small molecules in the environment. Hence, metabolism has 1. An energy-generating component, called catabolism (typically involving the destruction of organic material) , and 2. An energy-consuming, biosynthetic component, called anabolism . All Metabolic Processes Use chemical energy and related transformations to: 1. gather and store energy 2. transport energy 3. release energy to carry out a specific task At the heart of these mechanisms is ATP and ADP ADP = adenosine (C 10 H 13 N 5 O 4 ) diphosphate ATP = adenosine triphosphate Inter-conversion of ADP and ATP allow cells/organisms to store, transport, and release energy. ADP + PO 4 2- + Energy ATP + H 2 O ATP + H 2 O ADP + PO 4 2- + Energy ATP consists of a base, in this case adenine (red), a ribose (magenta) and a phosphate chain (blue). http://www.bristol.ac.uk/Depts/Chemistry/MOTM/atp/atp1.htm ATP (Charged form of energy) Mechanical Work (i.e., contraction ) Osmotic Work (i.e., transport) Wastes CO H O O Carbohydrates Fats Proteins Nucleic Acids 2 4 2 2 2- Biosynthesis ADP + PO (Spent form of energy) Mitochondria Fuels Carbohydrates Fats Proteins So the production of energy in an organism (or cell) is essentially equivalent to the generation of ATP from ADP (and vice versa) From Chameides, W.L. and E.M. Perdue, Biogeochemical Cycles: A Computer-Interactive Course in Earth System Science and Global Change,...
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- Spring '08