1. Biological Effects of Ionizing Radiation Effects of Radiation at the Molecular and Cellular Level Cell Biology Lecture IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources IAEA Post Graduate Educational Course in Radiation Protection and Safety of Radiation Sources

2. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level2 Introduction l This lecture presents information regarding basic knowledge of cell structure, which is necessary to know for the understanding of mechanism of radiation damage at the cellular level l It covers materials about functions of different organelles in the cell, cell cycle, cell division

3. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level3 Content l Cell structure l F unctions of different organelles l C ell cycle l Types of activities during cell division l Types of cell division

4. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level4 Overview l Cell – is a basic unit of life l Structure of cell – different organelles l Types of the cells

5. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level5 Cell structure

6. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level6 Stages of cell development l Formation of zygote l Multiplication of zygote by rapid cell division l Modification of the cells between division l Formation of the functionally different organs l Selective expression of genes l Change of the morphology of the cells to suit their function

7. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level7 Functions of different organelles l Cell membrane l Cytoplasm l Mitochondria l Nucleus l Endoplasmic reticulum l Lysosomes l Ribosomes

8. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level8 Cell membrane

9. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level9 Cytoplasm l Function of cytoplasm: n Contains organelles n Is the site of: sMany metabolic cycles sSynthetic pathways sTransport processes sSignaling processes

10. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level10 Mitochondria The matrix space contains a concentrated solution of many different enzymes The terminal stages of oxidation occur at the inner membrane Inner membrane folded into cristae Outer membrane

11. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level11 Mitochondria (Cont’d) l Functions of mitochondria: n “Powerhouse” of the cell n Synthesis of Adenosine triphosphate  oxidative phosphorylation process in the presence of oxygen  provides energy required for a variety of biochemical processes taking place in the cell (synthesis of various macromolecules such as DNA, RNA, proteins, etc

12. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level12 Nucleus Nuclear pores Chromatin Nucleolus Inner membrane Outer membrane

13. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level13 Nucleus (Cont’d) l Functions of nucleus: n Contains genetic information l Chromosome as a container of genetic information n Number of chromosomes in different species

14. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level14 Endoplasmic reticulum l Types of Endoplasmic reticulum: n Rough n Smooth l Functions of Endoplasmic reticulum: n Synthesis of proteins, hormones n Detoxification

15. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level15 Lysosomes & Ribosomes Lysosomes: n Contain hydrolytic enzymes n Digest microbes l Ribosomes: n Synthesis of proteins

16. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level16 Cytoskeleton 1. Microtubules 2. Actin filaments 3. Intermediate filaments 25 nm diameter 7 nm diameter 10 nm diameter

17. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level17 Cell cycle S (DNA synthesis)

18. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level18 Types of cell division l Mitosis n Is important for the growth of organism and replacement of lost cells. l Meiosis n Takes place only in the reproductive system for the production of gametes

19. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level19 Mitosis

20. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level20 Mitosis (Cont’d) l Stages of cell division cycle: presynthetic gap (G1 phase) presynthetic gap (G1 phase) synthesis phase (S phase) synthesis phase (S phase) post synthetic gap (G2 phase) post synthetic gap (G2 phase) mitotic phase (M phase) mitotic phase (M phase) l Stages of the mitotic phase: prophase prophase metaphase metaphase anaphase anaphase telophase telophase

21. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level21 Meiosis

22. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level22 Meiosis (Cont’d) l Duplication of DNA content l Process of two divisions l Four daughter cells are formed l Each daughter cell contains only one set of chromosomes l Meiotic division helps to conserve the chromosome number during reproduction process

23. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level23 Types of activities during cell division cycle l Growth cycle n cell growth n doubling of the cell components l Replication cycle n the actual DNA replication and cell division

24. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level24 Proliferation l G1 phase n G1A phase scontains most of the post-mitotic cells with protein and RNA levels lower than those of cells in S phase saccumulation of cellular components (RNA, proteins,...) until a threshold level is reached n G1B phase scontains cells with a protein and RNA level nearly the same as those cells already in S phase

25. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level25 Quiescence and Stop l Quiescence phase can be observed during S phase (SQ) and G2 phase (G2Q) l General characteristic: n DNA level normal for the phase n RNA level far below normal l Stop phase corresponds to the blockage of cells by the temporary or permanent action of toxic agents n could be seen in a various phases of the cell cycle n characterized by a metabolic imbalance

26. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level26 Gene expression l Each type of cell selectively expresses the genes associated with their function l Only a small fraction of the genes express in a particular type of cell l Genes: n promoters n regulators

27. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level27 Summary l This lecture presented materials about basic knowledge of cell structure as a ground for understanding of mechanism of radiation damage at the cellular level l The materials of the lecture should be learned at the introductory stage of radiobiology learning l Comments are welcomed

28. Module III.1 - Effects of Radiation at the Mollecular and Cellular Level28 Where to Get More Information l Cell and Molecular Biology, E.D.P. De Robertis V., De Robertis E.M.F., Infro- Med Ltd; Hong Kong (1998). l Physical and chemical mechanisms in molecular radiation biology. Glass W.A. and Varma M.N. Eds, Plenum Press, New York 1991. l Kiefer J. Biological Radiation effects. Springer Verlag, Berlin, Heidelberg 1990; 444. l IAEA Regional Basic Professional Training Course on Radiation Protection, India, 1998. Training Materials