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1、Microbial Metabolism,The metabolism of Microbes; The Pursuit and Utilization of Energy; Pathways of Bioenergetics; Biosynthesis and the Crossing Pathways of Metabolism;,Chapter Overview,Cells are constantly involved in an orderly activity called metabolism that encompasses all of their chemical and
2、energy transactions; Enzymes are essential metabolic participants that drive cell reactions; Enzymes are protein catalysts that speed up chemical processes by lowering the required energy;,Enzymes have a specific shape tailored to perform their actions on a single type of molecule called stustrate;
3、Enzymes derive some of their special characteristics from cofactors such as vitamins,and they show sensitivity to environmental factors; Enzymes are involved in activities that synthesize,digest,oxidize,and reduce compounds,and convert one substance to another;,Enzymes are regulated by several mecha
4、nisms that alter the structure of synthesis of the enzyme; The energy of living systems resides in the atomic structure of chemicals that can be acted upon and changed; Cell energetics involves the release of energy that powers the formation of bonds;,The energy of electrons is transferred from one
5、molecule to another in coupled redox reactions; Electrons are transferred from substrates such as glucose to coenzyme carriers and ultimately captured in high-energy adenosine triphosphate(ATP); Cell pathways involved in extracting energy from fuels are glycoysis,the tricarboxylic acid cycle,and ele
6、ctron transport;,The molecules used in aerobic respiration are guucose and oxygen ,and the products are CO2,H2Oand ATP; Microbes patrcipate in alternate pathways such as fermenation and anaerobic respiration; Cells manage their metabolites through linked pathways that have numerous functions and can
7、 procceed in more than one direction,The Metabolism of Microbes,Metabolism ,meaning change,pertains(适用 ) to all chemical reactions and physical workings of the cell.,Anabolism(合成代谢),It is any process that results in synthesis of cell molecules and structures.It is a building and bond-making process
8、that forms larger macromolecules from smaller ones ,and it usually requires the input of energy.,Anabolism is the set of metabolic pathways that construct molecules from smaller units. These reactions require energy. One way of categorizing metabolic processes, whether at the cellular, organ or orga
9、nism level is as anabolic or as catabolic, which is the opposite. Anabolism is powered by catabolism, where large molecules are broken down into smaller parts and then used up in respiration. Many anabolic processes are powered by adenosine triphosphate (ATP).,Anabolic processes tend toward “buildin
10、g up“ organs and tissues. These processes produce growth and differentiation of cells and increase in body size, a process that involves synthesis of complex molecules. Examples of anabolic processes include the growth and mineralization(矿化 ) of bone and increases in muscle mass.,Catabolism（分解代谢）,Ca
11、tabolic reactions are degradative;they break the bonds of larger molecules into smaller molecules,and often produce energy.,Catabolism is the set of metabolic pathways which break down molecules into smaller units and release energy.In catabolism, large molecules such as polysaccharides, lipids, nuc
12、leic acids and proteins are broken down into smaller units such as monosaccharides, fatty acids, nucleotides and amino acids, respectively. As molecules such as polysaccharides(多聚糖), proteins and nucleic acids are made from long chains of these small monomer units, the large molecules are called pol
13、ymers .,Cells use the monomers released from breaking down polymers to either construct new polymer molecules, or degrade the monomers further to simple waste products, releasing energy. Cellular wastes include lactic acid, acetic acid, carbon dioxide, ammonia, and urea.,The creation of these wastes
14、 is usually an oxidation process involving a release of chemical free energy, some of which is lost as heat, but the rest is used to drive the synthesis of adenosine triphosphate (ATP).,This molecule acts as a way for the cell to transfer the energy released by catabolism to the energy-requiring rea
15、ctions which make up anabolism. Catabolism therefore provides the chemical energy necessary for the maintenance and growth of cells.,Examples of catabolic processes include glycolysis(糖酵解), the citric acid cycle, the breakdown of muscle protein in order to use amino acids as substrates for gluconeog
16、enesis and breakdown of fat in adipose tissue to fatty acids.,In summary ,metabolism performs these functions:,Degrades macromolecules into smaller molecules and releases energy; Energy that is released is converted into ATP or released as heat; The smaller molecules are assembled to form larger mac
17、romolecules specific to the cell and in this process ATP is utilezed to form bonds.,Simplified Model of Metabolism,It has built-in controls for reducing or stopping a process that is not in demand and other controls for storing excess nutrients.The metabolic working of the cell are indeeed intricate(精细的) and complex,but they are also elegant and efficient.It is this very organization that sustains life.,
