Chapter 7 - Membrane Structure Flashcards
Having both a hydrophilic and hydrophobic region
Amphipathic
The plasma allows some substances to cross it more easily than others
Selective permeability
Currently accepted model of the cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids
Fluid mosaic model
Proteins that penetrate the hydrophobic interior of the lipid bilayer; majority are transmembrane proteins
Integral proteins
Proteins not embedded in the lipid bilayer at all; they are appendages loosely bound to the surface of the membrane often to expose parts of integral proteins
Peripheral proteins
Short, branched chains of carbohydrates covalently bonded to lipids
Glycolipids
Short, branched chains of carbohydrates covalently bound to proteins
Glycoproteins
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane
Transport proteins
Channel protein that facilitates the passage of water molecules through the membrane in certain cells; allows up to 3 billion water molecules per second
Aqua poring
Movement of particles of any substance so that they spread out into the available space
Diffusion
Region along which the density of a chemical substance increases or decreases
Concentration gradient
Diffusion of free water across a selectively permeable membrane whether artificial or cellular
Osmosis
The ability of a surrounding solution to cause a cell to gain or lose water
Tonicity
No net movement of water across the cell membrane; equal solutes
Isotonic
Solution causing a cell to lose water due to higher concentration of solutes outside the cell
Hypertonic
Solutions causing cell to take up water due to lower concentration of solutes outside the cell
Hypotonic
Control of solute concentrations and water balance
Osmoregulation
very firm; healthy state for most plants (hypotonic)
Turgid
Limp; no net tendency for water to enter the plant cell (isotonic)
Flaccid
Process causing a plant to wilt and can lead to death; caused by hypertonic conditions
Plasmolysis
Polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins that span the membrane
Facilitated diffusion
Channel proteins that transport ions
Ion channels
Ion channels that open or close in response to stimulus
Gated channels
Movement of a solute across a membrane against its gradient requiring the expenditure of energy
Active transport