Biology 121 Chapter 7
Terms in this set (43)
That is, it allows some substances to cross it more easily than others
Meaning it has both hydrophobilic("water-loving") region and hydrophobic("water-fearing") region
Fluid Mosaic Model
The membrane is mosaic of protein molecules bobbing in a fluid nilayer of phospholipids
Unsaturated hydrocarbon tails(kinked) prevent packing, enhancing membrane fluidity
Saturated hydrocarbon tails pack together, increasing membrane viscosity
Penetrate the hydrophobic interior of the lipid bilayer
Are not embedded in the lipid bilayer at all; they are loosely bound of the surface of the membrane, often to exposed parts of integral proteins
A protein hat spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute. Other transport proteins shuttle a substance from one side to the other by changing shape. Some as an energy source to actively pump substances across the membrane
A protein built into the membrane may be an enzyme with active site (where the reactant binds) exposed to the substances in the adjacent solution.
A membrane protein (receptor) may have a binding site with a specific shape that fits the shape of a chemical messenger, such as a hormone. The external messenger (signaling molecules) may cause the protein to change shape, allowing it to relay the message to inside of the cell, usually by binding to the cytoplasmic protein
Some glycoprotein serve as identification tags that are specifically recognized by membrane proteins of other cells(short term)
Membrane proteins of adjacent cells may hook together in various kinds of junctions, such as gap junctions or tight junctions(long term)
Membrane carbohydrates are usually short, branched chains of fewer than 15 sugar units. Some are covalently bonded to lipids, forming molecules
Most are covalenty bonded to proteins
These hydrophilic substances can avoid contact with the lipid bilayer by passing through it that spans the membrane
The passage of water molecules throught the membrane in certain cells is greatly facilitated by channel proteins
The movement of particles of any substance so that they spread out into the available space
The region along which the density of a chemical suntance increases or decreases
The diffusion of a substance across a biological membrane, because the cell does not have to expend energy to make it happen
The diffusion of free water across cell membrane, whether artificial or cellular
The ability of surrounding solution to cause a cell to gain or lose water.
If a cell without a cell wall is imersed in an environment that the cell has the same amount of water there will be no net movement of water across the plasma membrane
The cell will lose water, shrivel, and probably die
Water will enter the cell faster than it leaves, and the cell will swell and lyse(burst) like an overfilled water balloon
The control of solute concentrations and water balance
(very firm) Healthy state for most plant cells
(limp)The plant wilts
This happens when a cell shrinks inside its cell wall while the cell wall remains intact.
many polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins that span the membrane
channel proteins that transport ions
A protein channel in a cell membrane that opens or closes in response to a particular stimulus.
The transport proteins that move solutes against their concentration gradients are carried proteins rather than channel proteins
Can induce the proteins to change shape in a manner that translocates a solute bound to the protein across the membrane. Exchanges Na+ and K+ across the plasma membrane of animal cells
The voltage across a cell's plasma membrane.
Combination of forces acting on an ion
A transport protein that generates voltage across a membrane
The main electrogentic pump, of plants, fungi, and bacteria
A transport protein can couple the "downhill" stance against its own concentration gradient
The cell secretes certain molecules by the fusion of vesicles with plasma membrane.
The cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane
A cell engulfs a particle by extending pseudopodia around it and packaging it within a membranous sac called a food vacuole
A cell continually "gulps droplets of extracellular fluid into tiny vesicles, formed by inholdings of the plasma membrane
Specialized type of pinocytosis that enables the cell to acquire bulk quantities of specific substances, even though those substanes may not be very concentrated in the extracellular fluid