Cells & Tissue Level of Organization

• Cell division


  One cell divides into two identical cells
• Cell biology or cytology


  The study of cellular structure and function
• Main parts of the cell

  • Plasma Membrane
  • Cytoplasm
  • Cytosol
  • Organelles
  • Nucleus
  • Chromosomes
  • Genes
• Cells


  Living structural and functional units enclosed by a membrane
• Plasma Membrane


  • Forms the cell’s flexible outer surface, separating the cell’s internal environment from the external environment
  • Selective barrier (semi-permeable) that regulates the flow of materials into and out of a cell
  • Selectivity helps establish and maintain the appropriate environment for normal cellular activities
• Membrane structure

  Consists of a lipid bilayer made up of phospholipids, cholesterol, and glycolipids
• Fluid mosaic model

  • The arrangement of molecules within the membrane resembles a sea of lipids containing many types of proteins
  • Lipids act as a barrier to certain substances
  • Proteins act as “gatekeepers” to certain molecules and ions
• Membrane Proteins

  • Integral Protein extends into or through the lipid bilayer among the fatty acid tails and are firmly embedded in it
  • Transmembrane proteins are integral proteins which span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid
  • Peripheral Protein not as firmly embedded in the membrane, attached to the polar heads of membrane lipids or to integral proteins at the inner or outer surface of the membrane
• Membrane Proteins

  • Glycoprotein membrane proteins with a carbohydrate group attached that protrudes into the extracellular fluid, carries N- and O-glycosidically linked carbohydrate chains
  • Glycocalyx the “sugary coating” surrounding the membrane made up of the carbohydrate portions of the glycolipids and glycoproteins
• Tonicity


  Relates to how a solution influences the shape of body cells
• Enzymes

  • Catalyze specific chemical reactions at the inside or outside surface of the cell
• Cell Identity Markers


  • Enable a cell to (1) recognize other cells of the same kind during tissue formation or (2) recognize and respond to potentially dangerous foreign cells
• Ligand


  Binding of a specific molecule to a receptor
• Parts of the cell

  • Cytoplasm
  • Cytosol
  • Organelles
• Receptors

  • Serve as cellular recognition sites
• Membrane proteins


  • Transporters
• Osmosis


  The net movement of a solvent through a selectively permeable membrane from an area of high concentration to an area of low concentration. In living systems, the solvent is water, which moves by osmosis across plasma membranes from an area of higher water concentration to an area of lower water concentration
• Cytosol


  The fluid portion of cytoplasm, contains water, dissolved solutes, and suspended particles
• Tonicity of a solution

  • Isotonic Solution
  • Hypotonic Solution
  • Hypertonic Solution
• Linkers


  • Anchor proteins in the plasma membranes of neighboring cells to one another or to protein filaments inside and outside the cell
• The cytosol (intracellular fluid) surrounds organelles and constitutes about 55% of total cell volume. It is 75–90% water plus various dissolved and suspended components including ions, glucose, amino acids, fatty acids, proteins, lipids, ATP, and waste products. The cytosol is the site of many chemical reactions required for a cell’s existence
• Cytoskeleton

  A network of protein filaments that extends throughout the cytosol
• Cytoskeleton components

  • Microfilaments
  • Intermediate Filaments
  • Microtubules
• Protein Filaments

  • Microfilaments are the thinnest elements of the cytoskeleton, composed of the proteins actin and myosin, prevalent at the edge of a cell. They help generate movement and provide mechanical support
• Lysosomes
• Centrioles


  Cylindrical structures, each composed of nine clusters of three microtubules (triplets) arranged in a circular pattern
• Pericentriolar material

  1. Contains hundreds of ring-shaped complexes composed of the protein tubulin

  2. Organizing centers for growth of the mitotic spindle and for microtubule formation in nondividing cells
• Parts of the cell

  • Centrosome
  • Centrioles
  • Pericentriolar material
  • Nucleus
  • Chromosome
  • Ribosomes
  • Endoplasmic Reticulum
  • Lysosomes
• Intermediate Filaments


  • Thicker than microfilaments but thinner than microtubules
• Nucleus is a large organelle that houses most of a cell’s DNA
• Microfilaments


  • Composed of the proteins actin and myosin
  • Most prevalent at the edge of a cell
  • Help generate movement and provide mechanical support
• Chromosome is a single molecule of DNA associated with several proteins, contains thousands of hereditary units called genes. Genes control most aspects of cellular structure and function
• Centrosome


  Consists of two components: a pair of centrioles and pericentriolar material
• Microtubules

  • Largest of the cytoskeletal components
  • Long, unbranched hollow tubes composed mainly of the protein tubulin
• Endoplasmic Reticulum
• Phases of Cell Cycle
• Cell Division
• Mitosis is a type of cell division where the parent cell divides and each of the two daughter cells receives a chromosomal set identical to that of the parent cell (diploid)
• Meiosis is also known as reduction division. It reduces the number of chromosomes in the parent cell by half and produces four gamete cells (haploid). It occurs only in gametes or sex cells
• Types of Cell Division