how thick is the plasma membrane?
what is a special characteristic of the plasma membrane and that does it mean?
-selective permeability-allows some substance to cross it more easily than others
what are the main ingredients of membranes?
lipis and proteins
what are the most abundent lipids in membranes?
what is an amphipathic molecule?
has both a hydrophilic region and a hydrophobic region
fluid mosaic model
-various proteins embedded in or attached to a double layer (bilayer) of phospholipids.
-lipis (phospholipids) has cholesterol lipids stuck in between
-carbohydrate (outside)-establish identity foe cell
-cholesterol helps stabilize lipid bilayer
inbetween lipid bilayer
on one side or other,
-often to expose parts of integral protein
sugar units covalently bonded to lipids
-on extracellular side of the plasma membrane use them to distinguish one cell from another
permeability of lipid bilayer
only hydrophobic and slightly charged molecules are permeable
a protein that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute
transport protein for water
-the passage of water molecles through the membrane in certain cells is greatly facilitated by channel proteins
-no energy needed
-diffusion of a substance across a membrane with no energy investement
holds on to their passengers and change shape in a way that shuttles them across the membrane.
-made for only a certain kind of substance that it will shuttle
the movement of molecules of any substance so that they spread out evenly into the available space
the region along which the density of a chemical substance decreases
diffusion of water molecules along semipermeable membrane
what are the kinds?
the ability of a solution to cause a cell to lose or gain water.
(remember opposited, goes to solute)
hypotonic-lysed, turgid (normal)
polar molecules and ions imoeaded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins that span the membrane
uses energy to move solutes against their gradients
a single ATP powereed pump that transports a specific solute can indirectly drive the active transport of several other solutes in a solution.