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Radiation Biology

Radiation Biology. Chapter 5: Overview of Cell Biology Laura herz , BA, RT (R). The Cell. Cell is the fundamental component of structure, development, growth, and life processes in the body Body is composed of trillions of cells Some are freely moving, independent units

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Radiation Biology

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  1. Radiation Biology Chapter 5: Overview of Cell Biology Laura herz, BA, RT (R)

  2. The Cell • Cell is the fundamental component of structure, development, growth, and life processes in the body • Body is composed of trillions of cells • Some are freely moving, independent units • Some remain in position as part of tissues • Cells are engaged in an ongoing process of obtaining energy and converting it to support their functions • If exposure to ionizing radiation damages the cell beyond repair, cells behave abnormally or die

  3. Cell Chemical Composition • Cells are made of protoplasm--the chemical building material for all living things • Protoplasm consists of: • Organic compounds • Inorganic compounds • Water

  4. Organic Compounds • Compounds that contain carbon • Four major classes: • Proteins • Carbohydrates • Lipids • Nucleic acids

  5. Organic Compounds • Proteins • Make up about 15% of cell content • Essential for growth, construction of new body tissue, and the repair of injured tissue

  6. Organic Compounds • Proteins (cont.) • Formed when amino acids are connected by __________ ________into long, chainlike configurations • The order of arrangement of amino acids determines the precise function of each protein • Structural Proteins: provide the body with shape and form; source of heat and energy • Enzymatic Proteins: function as catalysts—agents that speed up reactions to meet the needs of the cell • Repair Enzymes: can mend damaged molecules and are therefore capable of helping the cell to recover from a small amount of radiation-induced damage • Hormones: chemical secretions carried by the bloodstream to influence the activities of other parts of the body • Antibodies: chemically attack any foreign invaders or antigens

  7. Organic Compounds • Carbohydrates • Make up about 1% of cell content • Function as energy sources for the body

  8. Organic Compounds • Lipids • Also referred to as fats • Make up about 2% of cell content • Functions: • Structural component of cell membranes • Insulate and guard the body against the environment • Support and protect organs

  9. Organic Compounds • Nucleic Acids • Comprise about 1% of the cell • Two important types: • Deoxyribonucleic acid (DNA) • Ribonucleic acid (RNA)

  10. Organic Compounds • Nucleic Acids (cont.) • DNA • Master chemical because it carries the genetic information necessary for cell replication and regulates all cellular activity to direct protein synthesis • Coiled, ladder-like structure • Composed of two long sugar-phosphate chains (sides) linked by pairs of nitrogenous bases (steps or rungs) • Bases are divided as: • Purines: • Pyrimidines: • Purines link with pyrimidines in certain specific combinations • Adenine always bonds with thymine • Cytosine always bonds with guanine

  11. Organic Compounds • Nucleic Acids (cont.) • RNA • Helps DNA influence cellular activity that takes place outside the nucleus • Messenger RNA (mRNA) • Directs the process of making proteins out of amino acids • Transfer RNA (tRNA) • Receives the genetic code from mRNA in the correct order so that the necessary proteins are produced

  12. Inorganic Compounds • Compounds that do not contain carbon • Consist of: • Acids • Bases • Salts (Electrolytes) • Maintain proper proportion of water in the cell • Aid in the production of energy • Aid in the conduction of nerve impulses

  13. Cell Structure • Cell Membrane • Cytoplasm • Cytoplasmic Organelles • Endoplasmic reticulum • Golgi apparatus or Golgi complex • Mitochondria • Lysosomes • Ribosomes • Nucleus • Nucleolus

  14. Cell Structure • Cell Membrane • Semi-permeable structure encasing the cell • Made up of lipids and proteins • Protects cellular contents from outside environment and controls the passage of materials into and out of the cell

  15. Cell Structure • Cytoplasm • Fluid inside the cell membrane, but outside of the nucleus • Primarily composed of water and makes up the majority of the cell • Contains large amounts of cell’s molecular components except DNA • Where all metabolic functions occur

  16. Cell Structure • Endoplasmic Reticulum • Network of tubules and vesicles throughout the cytoplasm • Enables cell to communicate with outside environment and transfer food and molecules from one part of the cell to another • “Highway System” • Two types • Smooth Endoplasmic Reticulum: • Rough Endoplasmic Reticulum:

  17. Cell Structure • Golgi apparatus or Golgi complex • Consist of tubes and a tiny sac near the nucleus • Unites large carbohydrate molecules with proteins to form glycoproteins • Takes enzymes and hormones and concentrates, packages, and transports them through the cell membrane so they can exit the cell and enter the bloodstream • “Packaging and Shipping Plant”

  18. Cell Structure • Mitochondria • Large, oval or bean-shaped structures • Supply energy for cells • “___________________” of the cell

  19. Cell Structure • Lysosomes • Small, pea-like sacs that are of great importance for digestion within the cytoplasm • Break down large, unwanted molecules • Sometimes referred to as “___________ ______”

  20. Cell Structure • Ribosomes • Small, spherical organelles that attach to the Endoplasmic Reticulum • “__________ ______________”

  21. Cell Structure • Nucleus • Separated from other parts of the cell by the nuclear membrane • Controls cell division • Controls chemical reactions that occur in the cell

  22. Cell Structure • Nucleolus • Small, rounded body within the nucleus • Manufactures RNA

  23. Cell Division • Multiplication process whereby one cell divides to form two or more cells • Two types occur in the body • Mitosis (M) • Somatic cells • Meiosis • Genetic cells

  24. Mitosis • Cell divides to form two daughter cells identical to the parent cell • Process results in an approximately equal distribution of all cellular material between the two daughter cells

  25. Mitosis • Interphase • G1 • S • G2 • Mitosis Phase • Prophase • Metaphase • Anaphase • Telephase

  26. Mitosis • Interphase • Period of cell growth that occurs before mitosis • Cells are not yet undergoing division • G1: Pre-DNA synthesis • May take a few minutes to several hours • S: DNA synthesis • Takes up to 15 hours • G2: Post-DNA synthesis • Occupies 1 to 5 hours of the whole cycle

  27. Mitosis • Mitosis Phase • Prophase: Nucleus and chromosomes enlarge, centrioles migrate to opposite sides of cell • Metaphase: Mitotic spindle forms between centrioles, chromosomes line up in the center of the cell • Anaphase: Chromatids travel to opposite sides of the cell • Telophase: Chromatids uncoil, nuclear membrane re-forms, two nuclei appear • After division completes, each daughter cell has a complete cell membrane and contains 46 chromosomes (exactly the same as the parent cell)

  28. Meiosis • Reduces the number of chromosomes in each daughter cell to half the number of chromosomes in the parent cell • Process of ___________ ___________

  29. Meiosis • Interphase • DNA replication • Cells begin meiosis with twice the genetic material as the parent cell • Prophase • Metaphase • Anaphase • Telophase • Divides again without DNA replication

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