chapter 5 Flashcards
Selective Permeability
Allowing some substances to cross the plasma membrane more easily than others.
Amphipathic
Molecules containing hydrophobic and hydrophilic regions (e.g. phospholipids).
Fluid Mosaic Model
States that the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.
Integral Proteins
Penetrate the hydrophobic interior of the lipid bilayer.
Peripheral Proteins
Are loosely bound to the surface of the membrane.
Six major functions of membrane proteins
Transport, Enzymatic activity, signal transduction, cell to cell recognition, intercellular joining, attachment to the cytoskeleton and extracellular matrix (ECM)
Transport Proteins
Allow passage of hydrophilic substances across the membrane.
Aquaporins
Channel proteins which facilitate the passage of water through the membrane.
Diffusion
The tendency for molecules to spread out evenly into the available space.
Concentration Gradient
Diffusion from where a substance is more concentrated to where it is less concentrated.
Passive Transport
The diffusion of a substance across a biological membrane. No energy is expended by the cell.
Osmosis
The diffusion of free water across a selectively permeable membrane.
Tonicity
The ability of a surrounding solution to cause a cell to gain or lose water.
Isotonic Solution
Solute concentration is the same as inside the cell.
Hypertonic Solution
Solute concentration is greater than inside the cell. Cell loses water.
Hypotonic Solution
Solute concentration is less than that inside the cell. Cell gains water.
Osmoregulation
The control of solute concentrations and water balance.
Turgid
A plant cell in a hypotonic solution swells until the cell wall opposes water uptake.
Flaccid
A plant cell and its surroundings are isotonic, no net movement of water into the cell.
Plasmolysis
Plant cell loses water in a hypertonic solution causing the membrane to pull away from the cell wall.
Facilitated Diffusion
Transport proteins speed the passive movement of specific molecules across the plasma membrane.
Active Transport
Moves substances against their concentration gradients. Allows cells to maintain concentration gradients that differ from their surroundings.
Membrane Potential
A voltage across a membrane. Caused by differences in the distribution of anions and cations across the membrane.
Sodium-Potassium pump
One type of active transport system. Exchanges NA+ for K+ across the plasma membrane of animal cells.
