Skip to main content
Indietro

Chapter 3

I pulsanti di controllo sono stati cambiati in modalità "navigazione".
1/20

Termini in questo insieme (20)

  • What are the three main parts of a generalized cell?
    Plasma membrane (flexible outer boundary), cytoplasm (gelatin-like substance with organelles), and nucleus (contains genetic material).
  • What is the primary function of the plasma membrane?
    It acts as an active barrier that covers and protects the cell, controls entry and exit of substances, and facilitates communication with other cells.
  • Describe the structure of the plasma membrane.
    A lipid bilayer made of phospholipids with polar hydrophilic heads and nonpolar hydrophobic tails, embedded with integral and peripheral proteins and cholesterol.
  • What role does cholesterol play in the plasma membrane?
    Cholesterol makes the membrane stronger but less fluid, helping preserve membrane structure and functionality.
  • What are the two main types of proteins in the plasma membrane?
    Integral proteins that span the bilayer and peripheral proteins that attach loosely to the membrane surface.
  • What are cell junctions and their general function?
    Contact points between plasma membranes of tissue cells that allow adherence or communication between cells.
  • What are tight junctions?
    Junctions where integral proteins of adjacent cells fuse to form an impermeable barrier preventing fluid and molecule passage between cells.
  • Describe desmosomes and their function.
    Anchoring junctions where linker proteins interlock like a zipper, connected to keratin filaments, providing mechanical strength to tissues.
  • What are gap junctions?
    Communicating junctions formed by connexons that create tunnels allowing small molecules and ions to pass quickly between cells.
  • What is selective permeability of the plasma membrane?
    The membrane permits some substances to pass more readily than others, allowing nutrients in, wastes out, and retaining valuable molecules.
  • Define concentration gradient and electrical gradient.
    A concentration gradient is a difference in chemical concentration; an electrical gradient is a difference in electrical charge across a membrane.
  • What is passive transport?
    Movement of substances across membranes without energy use, moving down their concentration gradient.
  • What is active transport?
    Energy-requiring process that moves substances against their concentration gradient, often using ATP.
  • Explain diffusion across a membrane.
    Movement of solutes from an area of high concentration to low concentration until equilibrium is reached.
  • What is osmosis?
    The net movement of water through a selectively permeable membrane from an area of high water concentration to low water concentration.
  • How does tonicity affect cells?
    Tonicity describes how a solution affects cell fluid volume and pressure, influencing water movement into or out of cells.
  • What is the sodium-potassium pump?
    A primary active transport system that uses ATP to pump 3 Na+ out and 2 K+ into the cell, maintaining membrane potential.
  • What are antiporters and symporters in secondary active transport?
    Antiporters move two substances in opposite directions; symporters move two substances in the same direction across the membrane.
  • How does digitalis affect the sodium-potassium pump?
    Digitalis inhibits the Na+/K+ pump, causing Na+ accumulation inside heart cells, increasing Ca2+ and strengthening heart contractions.
  • What factors affect the rate of diffusion?
    Concentration gradient, temperature, molecular weight, surface area, and diffusion distance.