Exam 3 Flashcards
(54 cards)
Charles Overton (1890s)
Membranes are basically a lipid substance
Longmuir (1900s)
Lipids are phospholipids
Gorther & Grendel (1925)
Forms a lipid bilayer
Davson Danielli (1985)
Membranes contain proteins “protein sandwich model” proteins on outside
Robertson (1950s)
“Unit membrane” membranes function as an inseparable unit lie, membranes cannot be partial & still be functional
Hydrophobic tails
nonpolar
Hydrophilic
“polar heads” outside
Fluid Mosaic Model (1972) Singer & Nicholson
- characteristics of membranes are “two-dimensional fluids” (lipids and proteins flow laterally) composed of:
- Lipid bilayer: “fluid proteins embedded in the lipid bilayer like pieces of mosaic - membranes are asymmetric the two monolayers are composed of different lipids and proteins:
- Two “faces”
- Exoplasmic face (E face): faces “outside”
- Protoplasmic (P faces): also cytoplasmic face (C face): faces “inside”
Exoplasmic face (E face)
faces “outside”
Protoplasmic (P faces)
Also cytoplasmic face (C face): faces “inside”
Glycolipid
carbohydrate chains “antennae” - receptors sensors - environment
Hydrophobic force
holds the bilayer together
Chlorestrol
animal cell membranes only never plant cell fluidity
Transmembrane protein
all the way through. Many transmembrane proteins are transport proteins that facilitate proteins of chemicals through membrane
Channel proteins
small, inorganic molecules (porins, aquaporin) or ions (ion channels) by facilitated diffusion
integral proteins (transmembrane proteins)
partially or all the way through
uniport
one molecule one direction passing by facilitated diffusion
symport
2 molecules, same direction, one passing by facilitated diffusion the other by “piggyback”
antiport
2 molecules in opposite directions one passing by facilitated diffusion but generates energy to drive the other by active transport in the other direction
Carrier proteins (transporters permeases)
large organic molecules by various mechanisms passing facilitated diffusion or by active transport, except never by ATP hydrolysis
Diffusion
sometimes called simple diffusion to distinguish it from facilitated diffusion (later)
- the net, (no energy inherent tendency) movement that results from the random kinetic movement of individual molecules from a region of high to low concentrations
Measuring Diffusion
the rate of diffusion is a complex function of:
1. The concentration gradient
2. the “resistance” to flow a complex interaction of such characteristics
2.a) The physical and chemical properties of the medium through which the substance is diffusing (density, visiosity, polarity)
2.b) Molecular weight of the diffusing substance according to Graham’s law rate of diffusion
2.c) Temperature: increases the thermal agitation of all molecules
Facilitated Diffusion
The membrane protein “facilitated” diffusion through the membrane by opening a “tunnel”
Osmosis
The diffusion of a solvent through a semi-permeable membrane
- permeable to the solvent (water solvent can pass through) not permeable to the solute (solute cannot pass through) high to low concentration of water
