BASIC CELLULAR BIOLOGY

• CELLS:

  • Basic membrane-bound unit that contains the fundamental molecules of life and of which all living things are composed
• TISSUES:

  • Structurally and functionally group of cells
• ORGAN:

  • Collection of tissues that structurally form a functional unit specialized to perform a particular function
• ORGAN SYSTEM:

  • Group of organs in which they work together to perform a specific function
• ORGANISM:

  • A body made up of organs, organelles or other parts that work together to carry on the various processes of life
• • Constitutes about 55% of total cell volume
  • Medium in which many of cell’s metabolic reactions occur

  b. ORGANELLES:

  • Little organs
  • Surrounded by cytosol
  • Specialized structures that perform various jobs inside cells
• PARTS OF A CELL:

  1. PLASMA MEMBRANE:

  • Fluid-mosaic lipid bilayer studded with proteins; surrounds cytoplasm
  • The membrane found in all cells that separates the interior of the cell from the outside environment
  • Semi-permeable
  • Protects cellular contents
  • Makes contact with other cells
  • Contains channels, transporters, receptors, enzymes, cell-identity markers, and linker proteins

  2. CYTOPLASM:

  • Provides a platform upon which other organelles can operate within the cell
  • Has two components:

  a. CYTOSOL (INTRACELLULAR FLUID):

  • Fluid portion of cytoplasm
• • Motile cell surface projections that contain 20 microtubules and basal body
  • Cilia move fluids over a cell’s surface; flagella move an entire cell
  • Flagella is much longer
  • Basal Body: microtubule-based organelles that assemble cilia and flagella

  d. RIBOSOME:

  • Composed of two subunits containing ribosomal RNA and proteins; may be free in cytosol or attached to rough ER
  • Responsible for protein synthesis
  • RNA: has a backbone made of alternating phosphate groups and sugar ribose
• • Phospholipids: amphiphilic molecules with hydrophobic fatty acid chains and hydrophilic moieties

  f. GOLGI COMPLEX:

  • Consists of 3-20 flattened membranous sacs called cisternae
  • Entry (cis) face accepts proteins from rough ER; medial cisternae form glycoproteins, glycolipids, and lipoproteins; exit (trans) face modifies the molecules further, then sorts and packages them for transport to their destinations

  g. LYSOSOME:

  • Digestive system of the cell
  • Vesicle formed from Golgi complex; contains digestive enzymes
• ORGANELLES INSIDE THE CELLS:

  a. CYTOSKELETON:

  • Network of three types of protein filaments:
  • Microfilaments: cell movements
  • Intermediate filaments: multiple strands of proteins pulled together
  • Microtubules: maintains cell shape
  • Maintains shape and general organization of cellular contents; responsible for cellular movements

  b. CENTROSOME:

  • A pair of centrioles and pericentriolar material
  • Centrioles: paired barrel-shaped organelles
  • Pericentriolar Material: cloud of proteins that surrounds the centriole

  c. CILIA AND FLAGELLA:
• • Protein Synthesis: a core biological process occurring inside cells, balancing the loss of regular proteins through production of new proteins

  e. ENDOPLASMIC RETICULUM:

  • Membranous network of flattened sacs or tubules
  • Rough ER: Covered by ribosomes and is attached to the nuclear envelope
  • Smooth ER: Lacks ribosomes
  • Nuclear Envelope: a highly regulated membrane barrier that separates the nucleus from the cytoplasm in eukaryotic cells
  • Glycoproteins: proteins containing glycans (oligosaccharide chains) attached to amino acid side chains
• • Degrades unneeded, damaged, or faulty proteins by cutting them into small peptides

  j. MITOCHONDRION:

  • Powerhouse of the cell
  • Generates most of the chemical energy needed to power the cell’s biochemical reaction
  • Consists of an outer and inner mitochondrial membrane, cristae, and matrix; new mitochondria form from pre-existing ones
  • Site of aerobic cellular respiration reactions that produce most of a cell’s ATP
  • Cristae: a fold in the inner membrane of a mitochondrion
  • Matrix: the space within the inner membrane
• • Fuses with and digests contents of endosomes, pinocytic vesicles, and phagosomes and transports final products of digestion into cytosol; digests worn-out organelles (autophagy), entire cells (autolysis), and extracellular materials

  h. PEROXISOME:

  • Also called microbodies
  • Vesicle containing oxidases (oxidative enzymes) and catalase (decomposes hydrogen peroxide); new peroxisomes bud from preexisting ones
  • Oxidizes amino acids and fatty acids; detoxifies harmful substances

  i. PROTEASOME:

  • Tiny barrel-shaped structure that contains proteases (proteolytic enzymes)
• NUCLEUS:

  • Large organelle that houses most of a cell’s DNA
  • Controls and regulates the activities of the cell
  • Within the nucleus, each chromosome a single molecule of DNA associated with several proteins, contains thousands of hereditary units called genes that control most aspects of cellular structure and function
• Cell Division:

  • Process by which cells reproduce themselves
  • Two types of CD: Somatic Cell division and reproductive cell division
• • Metabolically active cell duplicates organelles and cytosolic components
  • Replication of chromosomes begins
  • (cells that remain in the G1 phase for a very long time, and possibly never divide again, are said to be in the G0 phase)
  • S PHASE:
  • Replication of DNA and Centrosomes
  • G2 PHASE:
  • Cell growth, enzyme, and protein synthesis continue
  • Replication of centrosomes complete

  B. MITOTIC PHASE:

  • Parent cell produces identical cells with identical chromosomes; chromosomes visible under light microscope
  • MITOSIS:

  a. Prophase:
• SOMATIC CELL DIVISION:

  • An orderly sequence of events by which a somatic cell duplicates its contents and divides into two
  • Objective is to make two genetically identical cells from a single cell
  • Replaces dead or injured cells
  • Adds new cells for tissue growth

  * Somatic Cells: any cell other than the germ cell

  • Are diploid, meaning they contain two sets of chromosomes
  • 23 pairs of chromosomes

  A. INTERPHASE:

  • Period between cell divisions; chromosomes not visible under light microscope
  • G1 PHASE:
• • Chromatin fibers condense into paired chromatids; nucleolus and nuclear envelope disappear; each centrosome moves to an opposite pole of the cell

  b. Metaphase:

  • Centromeres of chromatid pairs line up at metaphase plate

  c. Anaphase:

  • Centromeres split
  • Identical sets of chromosomes move to opposite poles of cell

  d. Telophase:

  • Nuclear envelopes and nucleoli reappear; chromosomes resume chromatin form; mitotic spindle disappears
  • CYTOKINESIS:
• • Cytoplasmic Division; contractile ring forms cleavage furrow around the center of the cell, dividing cytoplasm into separate and equal portions
• REPRODUCTIVE CELL DIVISION:

  • Type of cell division that occurs in the gonads (ovaries and testes), it reduces the number of chromosomes in the parent cell by half and produces four gamete cells

  * Fertilization: union of two different gametes

  ➔ MEIOSIS I:

  a. Prophase I:

  • Extended phase in which the chromosomes shorten and thicken, the nuclear envelope and nucleoli disappear, and the mitotic spindle forms
  • The two sister chromatids of each pair of homologous chromosomes pair off, an event called synapsis; the resulting four chromatids form a structure called tetrad
• • Parts of the chromatids of two homologous chromosomes may be exchanged with one another. Such an exchange between parts of nonsister chromatids is termed crossing over

  b. Metaphase I:

  • The tetrads formed by the homologous pairs of chromosomes line up along the metaphase plate of the cell, with homologous chromosomes side by side

  c. Anaphase I:

  • Members of each homologous pair of chromosomes separate as they are pulled to opposite poles of the cell by the microtubules attached to the centromeres. The paired chromatids, held by a centromere, remain together.
• d. Telophase I:

  • Nuclear envelopes and nucleoli reappear; chromosomes resume chromatin form; mitotic spindle disappears

  ➔ CYTOKINESIS:

  • Cytoplasmic division; contractile ring forms a cleavage furrow around the center of the cell, dividing cytoplasm into separate and equal portions.

  ➔ MEIOSIS II:

  • Consists of 4 phases: Prophase II, Metaphase II, Anaphase II, Telophase II
  • These phases are similar to those that occur during mitosis; the centromeres split and the sister chromatids separate and move toward opposite poles of the cell
• COMPOSITION OF THE BODY

  1. ATOMIC COMPOSITION

  • determines the character and degree of radxn interacxn that occur.
• 2. Molecular and tissue composition 


  defines the nature of radxn exposure
• ***ULTIMATE GOAL OF RADBIOLOGICAL RESEARCH

  -accurately describe the effects of radxn in humans so that the radxn can be used more safely in dx and more effectively in therapy
• ATOMIC COMPOSITION

  60.00% HYDROGEN 0.2% CALCIUM

  25.7% OXYGEN 0.1% PHOSPHORUS 

  10.7% CARBON 0.1% SULFUR

  2.4% NITROGEN
• a)PLASMA /CELL MEMBRANE: a flexible yet sturdy barrier that surrounds and contain the cytoplasm of the cell

  b) CYTOPLASM: contains cytosol and organelles

  c)  NUCLEUS: contains the principal molecular component-DNA

      :also contains RNA,PROTEIN & WATER


  PROTOPLASM
• CYTOSOL

  • “intracellular fluid”
  • 55% of total cell volume
  • site of chemical reactions in a cell’s existence
  • building blocks for maintenance of cell structures and cell growth 
• MOLECULAR AND TISSUE COMPOSITION

  80 %- WATER

  15% - PROTEIN

  2% LIPIDS

  1% NUCLEIC ACID

  1% CARBOHYDRATES

  1% OTHER