Selective permeability: allows some substances to cross it more easily than others.
7.1 Cellular membranes are fluid mosaics of lipids and proteins
Membranes are composed of mostly lipids and proteins although carbs are an important factor as well.
Amiphipathic: has a hydrophobic and hydrophilic region.
Fluid mosaic model: membrane is fluid structure w/ various proteins embedded or attached to a bilayer of phospholipids.
Freeze fracture: splits a membrance along the middle of the bilayer for electron microscopy.
Cholesterol regulates the fluidity and temperature of membranes, "fluidity buffer"
Membrane Proteins
Integral: penetrate the hydrophobic interior of the lipid bilayer. The majority are transmembrane proteins which span the membrane.
-Hydrophobic regions of integral proteins consist of one or more stretches of nonpolar aa, usually coiled into alpha helices.
Some proteins have hydrophilic channels thru their center that allows for the passage of hydrophilic substances.
Peripheral: appendages loosely bound to the surface of the membrane.
Certain membrane proteins attach to fibers of the ECM to provide animals a stronger framework than just the plasma membrane.
*Carb covalently bond to proteins and lipids.
Glycoproteins on blood cells are markers for blood types: A,B,AB, O.
7.2 Membrane structures results in selective permeability
Nonpolar molecules such as hydrocarbons, carbon dioxide, and oxygen are hydrophobic and can therefore dissolve in the lipid bilayer of the membrane and cross it easily without the aid of membrane proteins.
Polar molecules pass thru slowly.
Transport proteins
Cell membranes are permeable to specific ions and a variety of polar molecules. Hydrophilic substances can avoid contact with lipid bilayer by passing thru transport proteins that span the membrane.
Channel proteins function by having a "by pass" that certain molecules or atomic ions use thru the membrane.
Carrier proteins change their shape to fit/ship their passengers.
7.3 Passive transport is a diffusion of a substance across a membrane with no energy investment
Diffusion: movement of molecules to evenly spread out
Concentration gradient: evenly spread the concentration of substance. High > low, low > high = even
Passive transport: diffusion of substance across a biological membrane where cell does not have to expend energy to make it happen.
Osmosis: diffusion of free water across a selectively permeable membrane.
Tonicity: ability of surrounding solution to cause a cell to either gain or lose water.
Isotonic: water tonicity is same - no "net movement"
Hypertonic: cell will lose water - shrivel
Hypotonic: cell will gain water - burst
Osmoregulations: control of solute concentrations and water balance.
Plant
Turgor pressure: opposes further water uptake
Turgid: - plump, juicy, firm. (Hypotonic environment)
Flaccid: limp (Isotonic)
Plasmolysis: wilt, die. (Hypertonic)
Facilitated diffusion: polar molecules and ions impeded by lipid bilayer diffuse passively with the help of transport proteins. (passive transport)
7.4 Active transport uses energy to move solutes against their gradients
Active transport: requires energy to pump solute across a membrane against its gradient. (carrier proteins)
Sodium potassium pump: 3Na+ out for every 2K+ in
Membrane potential: Energy source that affects the traffic of all charged substances across membrane
-Inside cell is (-) therefore cations are taken in and anions out.
Electrochemical gradient: chemical force(ion's concen. gradient) + electrical force(effect of membrane potential on ion's movement)
Proton pump: Fungi, plant, bacteria - pumping of H+ transfer (+) from cytoplasm to extracellular solution.
Cotransplant: Active transport driven by concen.
7.5 Bulk transport across the plasma membrane occurs by exocytosis and endocytosis
Exocytosis: Cell transport out via vesicles
Endocytosis: cell transport in via vesicles
-Phagocytosis: cellular eating
-Pinocytosis: cellular drinking
-Receptor mediated endocytosis(RME):take in cholesterol for membrane synthesis and synthesis of other steroids.
Low density lipoproteins(LDL): Cholesterol travels in blood consisting on one protein & lipids.
