tailieunhanh - Radiation and Health - Chapter 12

Sinh học bức xạ - Cơ chế Trong chương này chúng tôi sẽ thảo luận về một số cơ chế cơ bản cho các hành động của bức xạ trên các hệ thống sinh học. Đang được thảo luận sẽ được phóng xạ có thể thay đổi hoặc hư hỏng các phân tử trong tế bào, làm thế nào có thể ảnh hưởng đến chu kỳ tế bào, và làm thế nào bức xạ hoạt động khi động vật và con người. Hấp thụ năng lượng bức xạ khởi tạo một số lượng lớn các quy trình trong một tế bào | Chapter 12 Radiation Biology Mechanisms In this chapter we will discuss some of the basic mechanisms for the action of radiation on biological systems. Under discussion will be how radiation can change or damage the molecules in a cell how it can influence the cell cycle and how radiation acts upon animals and humans. The absorption of radiation energy initiates a large number of processes in a cell. It may take some time weeks months and years before the biological result can be observed. This situation must not lead us to believe that nothing takes place in this latent period. The starting point is the absorption process see Figure . Radiation energy is deposited in the system and a number of primary products are formed. These products ions excited molecules and free radicals are very reactive with lifetimes in an ordinary cell of the order of a fraction of a second. Their reactions with molecules in the cell result in secondary processes which finally yield a macroscopic result such as cell death cancer or genetic change. The research fields called radiation research radiation biology or radiation sciences include physics chemistry biology and medicine and examine all of the processes shown in Figure . 2003 Taylor Francis 152 Radiation and Health PHYSICS CHEMISTRY BIOLOGY Radiation is absorbed Secondary reactions Biological effects initial products 1. ions 2. excited molecules 3. free radicals result in changes to 1. DNA 2. proteins 3. other molecules may give 1. cell death 2. mutations 3. cancer Days to years Less than seconds Less than a nanosecond T I M E A X I S Figure . The radiation-induced processes in a biological system. One hundred years of research on the applications of radiation have yielded a large amount of information. Early on it was observed that radiation sensitivity varied from one cell type to another and that the sensitivity was greatest for cells in rapid growth. This observation initiated the use of radiation in cancer .