tailieunhanh - ECOTOXICOLOGY: A Comprehensive Treatment - Chapter 4

Hóa sinh khám phá trong chương 3 là trung tâm đối với sự sống. Cũng rất cần thiết là những khác biệt không gian trong phân phối các hoạt động sinh hóa và moieties trong tế bào và mô. Ví dụ như sự khác biệt cần thiết trong hoạt động hô hấp trong ty thể so với hạt nhân, hoặc sự khác biệt tổng hợp glycogen trong gan so với các tế bào thận. Phức hợp đại phân tử hình thành màng, cơ quan tế bào, các nút di động, và ma trận ngoại bào tạo điều kiện thuận lợi. | 4 Cells and Tissues Cells are the site s of primary interaction between chemicals and biological systems. Segner and Braunbeck 1998 OVERVIEW The biochemistry explored in Chapter 3 is central to all life. Also essential are the spatial differences in the distribution of biochemical activities and moieties within cells and tissues. Examples include essential differences in respiratory activities within the mitochondria versus nucleus or glycogen synthesis differences in liver versus kidney cells. Macromolecular complexes forming membranes organelles cell junctions and extracellular matrices facilitate this spatial heterogeneity. Such differences emerging at the levels of the membrane organelle cell and tissue also produce spatial differences in effects of and responses to toxicants. Cyanide inhibits mitochondrial electron transport reactions by interfering with cytochrome a function. Methylated forms of arsenic can damage chromosomes localized in the nucleus and in so doing provide a mechanism for arsenic s carcinogenicity. Differences in the biochemical processes and moieties in various cell organelles determine the site of action for poisons such as cyanide and arsenic and spatial separation of cell types into different tissues determines which tissue is most affected by a toxicant or is most responsive to toxicant damage. High microsomal mixed function oxidase MFO activity in hepatocytes make liver tissue a major site of Phase I reactions. It also makes hepatocytes particularly prone to cancers initiated by strongly electrophilic metabolites of toxicants. High levels of metallothionein and lysosomal activity in vertebrate proximal tubules make renal damage an unfortunate consequence of acute cadmium poisoning. The extent of toxicant-induced cell death within a tissue and the tissue s regenerative capacity determine whether or not that tissue can support the proper functioning of the associated organ. Histopathology is the science that focuses on cellular and .