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TOXICOLOGICAL CHEMISTRY AND BIOCHEMISTRY - CHAPTER 4

Trao đổi chất trong sinh hóa môi trường sinh hóa thay đổi chất trải qua trong một sinh vật sống được gọi là trao đổi chất. Chuyển hóa mô tả các phản ứng dị hóa các loài hóa học được chia nhỏ bởi hành động của enzyme trong cơ thể để sản xuất năng lượng và các thành phần để tổng hợp phân tử sinh học cần thiết cho quá trình sống. Nó cũng mô tả các phản ứng đồng hóa, trong đó năng lượng được sử dụng để lắp ráp các phân tử nhỏ thành phân tử sinh học. | Chapter 4 Metabolic Processes 4.1 METABOLISM IN ENVIRONMENTAL biochemistry The biochemical changes that substances undergo in a living organism are called metabolism. Metabolism describes the catabolic reactions by which chemical species are broken down by enzymatic action in an organism to produce energy and components for the synthesis of biomolecules required for life processes. It also describes the anabolic reactions in which energy is used to assemble small molecules into larger biomolecules. Metabolism is an essential process for any organism because it provides the two things essential for life energy and raw materials. Metabolism is especially important in toxicological chemistry for two reasons 1 interference with metabolism is a major mode of toxic action and 2 toxic substances are transformed by metabolic processes to other materials that are usually though not invariably less toxic and more readily eliminated from the organism. This chapter introduces the topic of metabolism in general. Specific aspects of the metabolism of toxic substances are discussed in Chapter 7. 4.1.1 Metabolism Occurs in Cells Metabolic processes occur in cells in organisms. Figure 3.1 shows the general structure of eukaryotic cells in organisms such as animals and fungi. A cell is contained within a cell membrane composed of a lipid bilayer that separates the contents of the cell from the aqueous medium around it. Other than the cell nucleus the material inside the cell is referred to as the cell cytoplasm the fluid part of which is the cytosol. The cytosol is an aqueous solution of electrolytes that also contains enzymes that catalyze some important cell functions including some metabolic processes. Within the cytoplasm are specialized organelles that carry out various metabolic functions. Of these mitochondria are of particular importance in metabolism because of their role in synthesizing energetic adenosine triphosphate ATP using energy-yielding reactions. Ribosomes are .