BackAnatomy & Physiology: Cells and Membrane Transport
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Terms in this set (20)
A cell is the structural and functional unit of life. The organism's function depends on the activities of all its cells. Cells arise only from preexisting cells.
Plasma membrane (flexible outer boundary), cytoplasm (intracellular fluid with organelles), and nucleus (DNA-containing control center).
Substances outside cells including extracellular fluids (interstitial fluid, blood plasma, cerebrospinal fluid), cellular secretions (saliva, mucus), and extracellular matrix (glue holding cells together).
The plasma membrane is a selectively permeable lipid bilayer that separates intracellular fluid from extracellular fluid and controls what enters and leaves the cell.
The membrane consists of a lipid bilayer with floating specialized proteins that create a constantly changing mosaic pattern.
75% phospholipids (polar heads hydrophilic, nonpolar tails hydrophobic), 5% glycolipids, and 20% cholesterol which stabilizes the membrane.
Integral proteins span the membrane and function as transporters, enzymes, or receptors. Peripheral proteins attach loosely and support membrane structure and cell connections.
A sugar coating on the cell surface made of carbohydrates attached to lipids and proteins. It acts as a biological marker for cell recognition and immune system identification.
Tight junctions prevent fluid leakage, desmosomes provide mechanical strength, and gap junctions allow communication via small molecule passage.
Movement of substances down their concentration gradient without energy input, including simple diffusion, facilitated diffusion, and osmosis.
Concentration gradient, molecular size (smaller diffuses faster), and temperature (higher temperature increases diffusion speed).
Nonpolar, lipid-soluble substances like oxygen, carbon dioxide, steroid hormones, and small amounts of water.
Facilitated diffusion requires carrier proteins or channels to transport larger or polar molecules like glucose and ions down their concentration gradient.
Carrier-mediated uses protein carriers that change shape to move molecules; channel-mediated uses aqueous channels for ions or water.
Movement of solvent (usually water) across a selectively permeable membrane from an area of low solute concentration to high solute concentration.
Osmolarity measures total solute particles in solution. Higher solute concentration means lower water concentration, driving water movement by osmosis.
Tonicity is a solution's ability to change cell shape by altering water volume. Isotonic (no change), hypertonic (cell shrinks), hypotonic (cell swells).
Water enters the cell causing it to swell and potentially burst, a process called lysis.
Hydrostatic pressure pushes water out of the cell; osmotic pressure pulls water into the cell. Equilibrium occurs when these pressures balance.
Plant cell walls limit hydrostatic pressure, preventing excessive water intake and cell bursting.