ANAPHY Q3

• Cell biology


  Study of cellular structure and function
• Three main parts of a cell

  • Plasma membrane/Cell Membrane
  • Cytoplasm
  • Nucleus
• Cell membrane


  Forms the cell’s flexible outer surface, separates the cell’s internal environment from the external environment, regulates the flow of materials, measures about 5-10 nm in thickness, permits the passage of substances through it, is impermeable, exhibits selective permeability
• Fluid Mosaic Model


  • Molecular arrangement of the plasma membrane resembling an ever-moving sea of fluid lipids containing a mosaic of proteins
• Lipid Bilayer


  • Basic structural framework of the plasma membrane formed by two back-to-back layers of phospholipids, cholesterol, and glycolipids
• Phospholipid Bilayers


  Critical components of cell membranes, with hydrophobic tails facing each other and hydrophilic heads facing the internal and external parts of the cell
• Cholesterol


  Steroid lipid important for stabilizing the cell membrane and regulating membrane fluidity
• Carbohydrates


  Found on the exterior surface of cells, used for cell identification
• Integral membrane proteins


  Reside within bilayer membranes, play critical roles in movement of molecules across them and transduction of energy and signals
• Cell Membrane: Transport of materials into and out of cells


  Transport processes, description, substances transported
• Passive Processes


  Movement of substances down a concentration gradient until equilibrium is reached, do not require cellular energy in the form of ATP
• Diffusion


  Movement of molecules or ions down a concentration gradient due to their kinetic energy until equilibrium is reached, includes Simple Diffusion for nonpolar, hydrophobic solutes
• Simple Diffusion


  Passive movement of a substance down its concentration gradient through the lipid bilayer of the plasma membrane without the help of membrane transport proteins
• Nonpolar, hydrophobic solutes


  • Oxygen
  • Carbon dioxide
  • Nitrogen gases
  • Fatty acids
  • Steroids
  • Fat-soluble vitamins
  • Polar molecules such as water, urea, and small alcohols
• Facilitated Diffusion


  Passive movement of a substance down its concentration gradient through the lipid bilayer by transmembrane proteins that function as channels or carriers
• Polar or charged solutes for Facilitated Diffusion


  • Glucose
  • Fructose
  • Galactose
  • Some vitamins and ions such as K+, Cl-, Na+, and Ca^2+
• Osmosis


  Passive movement of water molecules across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration
• Solvent in living systems is water
• Active Processes require cellular energy in the form of ATP
• Active Transport


  Active process in which a cell expends energy to move a substance across the membrane against its concentration gradient by transmembrane proteins that function as carriers
• Polar or charged solutes for Active Transport


  • Na+, K+, Ca^2+, H+, I-, Cl-, and other ions
• Primary Active Transport


  Active process in which a substance moves across the membrane against its concentration gradient by pumps (carriers) that use energy supplied by hydrolysis of ATP
• Secondary Active Transport


  Coupled active transport of 2 substances across the membrane using energy supplied by a Na+ or H+ concentration gradient maintained by primary active transport pumps
• Types of Secondary Active Transport

  • Antiporters: move Na+ (or H+) and another substance in opposite directions across the membrane
  • Symporters: move Na+ (or H+) and another substance in the same direction across the membrane
• Transport in Vesicles


  Active process in which substances move into or out of cells in vesicles that bud from the plasma membrane, requiring energy supplied by ATP
• Endocytosis


  Movement of substances into a cell in vesicles
• Types of Endocytosis

  • Receptor-mediated endocytosis: Ligand-receptor complexes trigger infolding of a clathrin-coated pit that forms a vesicle containing ligands
  • Phagocytosis: Movement of a solid particle into a cell after pseudopods engulf it to form a phagosome
  • Bulk-phase endocytosis: Movement of extracellular fluid into a cell by infolding of plasma membrane to form a vesicle
• Exocytosis


  Movement of substances out of a cell in secretory vesicles that fuse with the plasma membrane and release their contents into the extracellular fluid
• Transcytosis


  Movement of a substance through a cell as a result of endocytosis on one side and exocytosis on the opposite side
• Cytoplasm consists of all the cellular contents between the plasma membrane and the nucleus
• Cytosol is the fluid portion of the cytoplasm that surrounds organelles and is the site of many chemical reactions required for a cell’s existence
• Cytosol constitutes about 55% of the total cell volume and consists of 75–90% water plus various dissolved and suspended components
• Organelles are specialized structures within the cytoplasm
• Intracellular fluid


  • The fluid portion of the cytoplasm that surrounds organelles
  • Site of many chemical reactions required for a cell’s existence
  • Constitutes about 55% of total cell volume
  • 75–90% water plus various dissolved and suspended components
• Organelles


  • Specialized structures within the cell that have characteristic shapes
  • Perform specific functions in cellular growth, maintenance, and reproduction
  • Each type has its own set of enzymes that carry out specific reactions and serves as a functional compartment for specific biochemical processes
  • Often cooperate to maintain homeostasis
• Cytoskeleton


  • Network of protein filaments that extends throughout the cytosol
  • Gives form and shape to the cell
• 3 Types of filamentous proteins contributing to the cytoskeleton’s structure

  • Microfilaments
  • Intermediate Filaments
  • Microtubules
• Microfilaments


  • Thinnest elements of the cytoskeleton
  • Composed of the protein actin, most prevalent at the edge of a cell
  • Involved in muscle contraction, cell division, and cell locomotion
  • Provide mechanical support and anchor the cytoskeleton to integral proteins in the plasma membrane
• Intermediate Filaments


  • Thicker than microfilaments but thinner than microtubules
  • Found in parts of cells subject to mechanical stress, help stabilize the position of organelles such as the nucleus, and help attach cells to one another
• Microtubules


  • Largest of the cytoskeletal components, long, unbranched hollow tubes composed mainly of the protein tubulin
  • Help determine cell shape and function in the movement of organelles, chromosomes during cell division, and specialized cell projections such as cilia and flagella