Chapter 7: Cell Membrane (Test 2) Flashcards
Phospholipids are the most abundant lipid in the plasma membrane
Phospholipids are ___ molecules, containing hydrophobic and hydrophilic regions
The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it
amphipathic
___ studies of the plasma membrane supported the fluid mosaic model
Freeze-fracture is a specialized preparation technique that splits a membrane along the middle of the phospholipid bilayer
Freeze-fracture
Phospholipids in the plasma membrane can move within the bilayer
Most of the phospholipids drift laterally, but rarely does a molecule flip-flop transversely across the membrane
Some proteins drift within the phospholipid bilayer
Other proteins never move and are anchored to the cytoskeleton below
As temperatures cool, membranes switch from a fluid state to a solid state
Components of membrane types of lipids
Membranes rich in unsaturated fatty acids are more fluid that those rich in saturated fatty acids
Cholesterol acts as a “temperature buffer” for the membrane
At warm temperatures (such as 37°C), cholesterol restrains movement of phospholipids
At cool temperatures, it maintains fluidity by preventing tight packing
___ proteins penetrate the hydrophobic core
___ proteins are bound to the surface of the membrane
Integral
Peripheral
Six major functions of membrane proteins:
- Transport
- Enzymatic activity
- Signal transduction
- Cell-cell recognition
- Intercellular joining
- Attachment to the cytoskeleton and extracellular matrix (ECM)
___ molecules, such as hydrocarbons, can dissolve in the lipid bilayer and pass through the membrane rapidly
___ molecules, such as sugars and ions do not cross the membrane easily
Hydrophobic (nonpolar)
Hydrophilic (polar)
___ is the tendency for molecules to spread out evenly. (molecules move from areas of higher to lower concentration)
Although each molecule moves randomly, diffusion of a population of molecules may exhibit a net movement in one direction
At ___ , as many molecules cross one way as cross in the other direction
Diffusion
dynamic equilibrium
Substances diffuse down their ___, the difference in concentration of a substance from one area to another
No work must be done to move substances down the concentration gradient
The diffusion of a substance across a biological membrane is ___ because it requires no energy from the cell to make it happen
concentration gradient
passive transport
___ is the diffusion of water across a selectively permeable membrane
Water diffuses across a membrane from the region of lower solute(higher water molecules) concentration to the region of higher solute (lower water molecules) concentration
Osmosis
___ is the ability of a solution to cause a cell to gain or lose water
Tonicity
___: Solute concentration is less than that inside the cell; cell gains water
Hypotonic solution
___: Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane
Isotonic solution
___: Solute concentration is greater than that inside the cell; cell loses water
Hypertonic solution