Cells

• Cell


  A living structural and functional unit that is enclosed by a membrane
• Main parts of a cell

  • Plasma membrane
  • Cytoplasm
  • Nucleus
• Plasma membrane


  The flexible outer surface of a cell that regulates the flow of materials into and out of the cell, and plays a key role in communication
• Plasma membrane


  • It is a lipid bilayer made up of phospholipids, cholesterol, and glycolipids
  • It contains integral and peripheral proteins
• Integral proteins


  Extend through the lipid bilayer and allow small and medium-sized water-soluble materials to cross the membrane
• Peripheral proteins


  Loosely attached to the exterior or interior surface of the membrane
• Selective permeability


  The plasma membrane allows some substances to move into and out of the cell but restricts the passage of other substances
• Cell


  A living structural and functional unit that is enclosed by a membrane
• Main parts of a cell

  • Plasma membrane
  • Cytoplasm
  • Nucleus
• Plasma membrane


  The flexible outer surface of a cell that regulates the flow of materials into and out of the cell, and plays a key role in communication
• Plasma membrane


  • It is a lipid bilayer made up of phospholipids, cholesterol, and glycolipids
  • It contains integral and peripheral proteins
• Integral proteins


  Extend through the lipid bilayer and allow small and medium-sized water-soluble materials to cross the membrane
• Peripheral proteins


  Loosely attached to the exterior or interior surface of the membrane
• Selective permeability


  The plasma membrane allows some substances to move into and out of the cell but restricts the passage of other substances
• Lipid bilayer


  Permeable to water and nonpolar molecules, but not permeable to ions and large, uncharged polar molecules
• Transport across the plasma membrane

  1. Movement of materials into the cell to support metabolic reactions

  2. Movement of materials out of the cell as waste products or for export
• Types of body fluids

  • Intracellular fluid
  • Extracellular fluid
  • Interstitial fluid
  • Blood plasma
  • Lymph
  • Cerebrospinal fluid
• Solute


  Any material dissolved in a fluid
• Solvent


  Fluid that dissolves materials
• Methods for substances to move across the plasma membrane

  • Passive processes (simple diffusion, osmosis)
  • Active processes (active transport)
• Diffusion


  A passive process in which a substance moves from an area of high concentration to an area of low concentration
• Simple diffusion


  Substances diffuse across the membrane through the lipid bilayer
• Facilitated diffusion


  Substances that cannot move through the lipid bilayer by simple diffusion cross the membrane with the assistance of an integral membrane protein
• Osmosis


  A passive process in which water moves through a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration
• Types of solutions


  • Isotonic
  • Hypotonic
  • Hypertonic
• Active transport


  An active process in which cellular energy is used to transport substances across the membrane against a concentration gradient
• Vesicle


  A small round sac formed by budding off from an existing membrane that transports substances within cells, takes in substances from extracellular fluid, and releases substances into extracellular fluid
• Endocytosis


  Materials move into a cell in a formed vesicle
• Phagocytosis


  Large solid particles, such as whole bacteria or viruses or dead cells, are taken in by the cell
• Bulk-phase endocytosis (pinocytosis)


  The cells take up tiny droplets of extracellular fluid
• Exocytosis


  Materials move out of a cell by the fusion of a vesicle
• Cytosol


  The liquid portion of the cytoplasm that surrounds organelles
• Cytoskeleton


  • Provides a structural framework for the cell and generates movements, composed of microfilaments, intermediate filaments, and microtubules
• Centrosome


  An organelle located near the nucleus that has two components - a pair of centrioles and pericentriolar material, and is the organizing center for growth of the mitotic spindle and microtubule formation
• Endoplasmic reticulum (ER)


  A network of folded membranes of flattened tubules, with rough ER studded with ribosomes that synthesize proteins, and smooth ER that synthesizes fatty acids and steroids
• Ribosomes


  The sites of protein synthesis, named for their high concentration of RNA molecules
• Cytoplasm


  • It is composed of a network of three different types of protein filaments: Microfilaments, Intermediate filaments, Microtubules
• Centrosome


  An organelle located near the nucleus, has two components - a pair of centrioles and pericentriolar material
• Centrosome


  • It is the organizing center for growth of the mitotic spindle, which plays a critical role in cell division, and for microtubule formation in nondividing cells
• Endoplasmic reticulum (ER)


  A network of folded membranes of flattened tubules