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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
• 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
CELL CHEMICAL COMPOSITION
• Cells are made of protoplasm--the chemical
building material for all living things
• Protoplasm consists of:
• Organic compounds
• Inorganic compounds
• Water
ORGANIC COMPOUNDS
• Compounds that contain carbon
• Four major classes:
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Proteins
Carbohydrates
Lipids
Nucleic acids
ORGANIC COMPOUNDS
• Proteins
• Make up about 15% of cell content
• Essential for growth, construction of new body tissue, and
the repair of injured tissue
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
ORGANIC COMPOUNDS
• Carbohydrates
• Make up about 1% of cell content
• Function as energy sources for the body
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
ORGANIC COMPOUNDS
• Nucleic Acids
• Comprise about 1% of the cell
• Two important types:
• Deoxyribonucleic acid (DNA)
• Ribonucleic acid (RNA)
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
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
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
CELL STRUCTURE
• Cell Membrane
• Cytoplasm
• Cytoplasmic Organelles
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Endoplasmic reticulum
Golgi apparatus or Golgi complex
Mitochondria
Lysosomes
Ribosomes
• Nucleus
• Nucleolus
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
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
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:
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”
CELL STRUCTURE
• Mitochondria
• Large, oval or bean-shaped structures
• Supply energy for cells
• “___________________” of the cell
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 “___________ ______”
CELL STRUCTURE
• Ribosomes
• Small, spherical organelles that attach to the Endoplasmic
Reticulum
• “__________ ______________”
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
CELL STRUCTURE
• Nucleolus
• Small, rounded body within the nucleus
• Manufactures RNA
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
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
MITOSIS
• Interphase
• G1
• S
• G2
• Mitosis Phase
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Prophase
Metaphase
Anaphase
Telephase
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
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)
MEIOSIS
• Reduces the number of chromosomes in each
daughter cell to half the number of chromosomes in
the parent cell
• Process of ___________ ___________
MEIOSIS
• Interphase
• DNA replication
• Cells begin meiosis with
twice the genetic material
as the parent cell
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Prophase
Metaphase
Anaphase
Telophase
• Divides again without DNA
replication