a plasma phospholipid bilayer controlling traffic into and out of the cell
allowing some substances to cross the membrane more easily than others
lipids and proteins
staple ingredients of a membranes
a phospholipid having a hydrophilic and hydrophobic region
fluid mosaic model
currently accepted model of a cell membrane structure. Envisions it as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids.
penetrate the hydrophobic core of the lipid bilayer
span the entire membrane, going through all layers of the cell membrane.
not embedded into the lipid bilayer AT ALL, appendages loosely bound to the surface of the membrane, often exposed to parts of the integral proteins.
transport, enyzmatic activity, signal transduction, cell to cell recognition, intercellular joining, attachment to cytoskeleton
6 major functions performed by proteins
a.) proteins that span the membrane can provide hydrophilic channel across the membrane. b.) others shuttle a substance from one side to the other by changing shape
ex: hydrolyzing ATP as an energy to actively transport substances across the membrane.
a protein built into the membrane may be an enzyme with its active site exposed to substances in the adjacent solution. also organize as a team to carry out metabolic pathways.
membrane protein called a receptor may have a binding site with a specific shape that fits the shape of a chemical messenger, such as a hormone. The signaling molecule may cause a shape change.
cell to cell recognition
some glycoproteins serve as identification tags that are specifically recognized by membrane proteins of other cells. distinguish one type of neighboring cell from another. basis for rejection of foreign cells.
membrane proteins of adjacent cells may hook together in various kinds of junction, i.e. gap junctions or tight junctions.
attachment to cytoskeleton
microfilaments or other elements of the cytoskeleton may be noncovalantly bound to membrane proteins, this helps maintain cell shape and stabalizes the location of certain membrane protens.
*Proteins that bind to Extra Cellular Membrane molecules can coor
a lipid with a covalently attached carbohydrates., membrane carbohydrates that are covalently bonded to lipids
a protein with one or more carbohydrate covalently attached to it. distinguish one cell from another.
transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane, lipid bilayer acts as gate keeper.
function by having a hydrophilic channel that certain molecules or atomic ions use as a tunnel thru the membrane
channel protein in plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of water across the membrane.
transport proteins that hold onto their passengers and change shape in a way that shuttles them across the membrane
molecules posses an energy called this, which results in diffusion
result of thermal motion, the movement of molecules of any substance so that they spread out evenly in the available space.
the region along which the density of a chemical substance decreases
the diffusion of a substance across a biological membrane. The cell does not ave to use energy to make it happen
the diffusion of water across a selectively permeable membrane, balance of water between cell and environment
the ability of a solution to cause a cell to gain or lose water
a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell, stableness
a solution that, when surrounding a cell, will cause the cell to lose water, causing a cell to die.
a solution that, when surrounding a cell, will cause the cell to take up water. water enters faster than it leaves causing the cell to burst
control of water balance
very firm cell in plants
limp cell in plants
the cytoplasm shrivels and the plasma membrane pulls away from the cell walls, when cell loses water to a hypertonic environment.
diffusion of molecules across the lipid bilayer with help from proteins
funciton as gated channels which open or close in response to a stimulus
movement of a substance across a cell membrane, with an expenditure of energy. to pump and solute across a membrane against its gradient requires work!
1. transport protein in plasma membrane that actively transports sodium out of the cell and potassium in.
voltage difference across cell membrane, inside is neg and outside is positive.
combinations of forces acting on an ion
2. transport protein that generates voltage across a membrane
3. occurs when active transport of a solute indirectly drives the transport of another solute
ex: active transport out and passive transport in
4. cell secretes certain biological molecules by the fusion of vesicles with the plasma membrane, removing from the cell
5. cell takes in biological molecules to form new vesicles from the plasma membrane.
cellular eating of solids
cellular drinking of liquids
enables cell to acquire bulk quantities of specific substances, even though those substance may not be very concentrated
any molecule that binds specifically to a receptor site of another molecule