Chapter 7 Flashcards
Aquaporin
A membrane protein that enables water molecules to pass through the membrane.
Amphipathic
Has both a hydrophilic region and a hydrophobic region
Fluid mosaic model
The membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.
A membrane is held together primarily by ____
Hydrophobic interactions
The membrane remains fluid to a lower temperature if it is rich in phospholipids with ….
Unsaturated hydrocarbon tails.
Cholesterol can be thought of as a…
Fluidity buffer for the membrane because it resists changes in membrane fluidity that can be caused by changes in the temperature.
Like a tile mosaic, a membrane is…
A collage of different proteins, often clustered together in groups, embedded in the fluid matrix of the lipid bilayer.
Proteins determine most of the membrane’s functions.
True
Integral proteins
Penetrate the hydrophobic interior of the lipid bilayer. Transmembrane proteins span through the entire membrane.
The hydrophobic interior of an integral protein consists of…
Non polar amino acids usually coiled into alpha helices
Peripheral proteins
Are not embedded in the lipid bilayer at all; they are appendages loosely bound to the surface of the membrane, often to exposed parts of integral proteins.
Six major functions performed by proteins of the plasma membrane
Transport
Enzymatic activity
Signal transduction
Cell-cell recognition
Intercellular joining
Attachment to the cytoskeleton and ECM
How membrane sidedness arises:
The asymmetrical arrangement of proteins, lipids, and their associated carbohydrates in the plasma membrane is determined as the membrane is being built by the ER and Golgi apparatus.
What molecules can cross the lipid bilayer of the membrane easily?
Non-polar, hydrophobic, molecules
The hydrophobic interior of the membrane impedes direct passage through the membrane of….
Ions and polar molecules, which are hydrophilic
Channel proteins
-Transport proteins
Have a hydrophilic channel
Ex. Aquaporins
Carrier proteins
-Transport protein
Hold onto their passengers and change shape in a way that shuttles them across the membrane.
The concentration gradient itself represents ___________ and drives diffusion
Potential energy
Tonicity
The ability of a surrounding solution to cause a cell to gain or lose water.
Non penetrating solutes
Concentration of solutes that cannot cross the membrane.
If there is a higher concentration of non-penetrating solutes in the surrounding solution,
Water will tend to leave the cell, and vice versa
In a solution that is hypertonic to the cell,
Hypertonic means
More non-penetrating solutes
-the cell will lose water
A solution that is hypotonic to the cell means
Less non-penetrating solutes
-Water will enter the cell
A cell without rigid cell walls can tolerate…
Neither excessive uptake nor excessive loss of water
Osmoregulation
The control of solute concentrations and water balance.
Cell wall helps maintain water balance
True
Healthy state for most plant cells:
Turgid in a hypotonic solution
Ion channels
Channel proteins that transport ions
Many ion channels function as ________
Gated channels
Gated channels
Open or close in response to a stimulus
Facilitated diffusion is considered passive transport because the solute is moving down its concentration gradient, a process that requires no energy.
True
The transport proteins that move solutes against their concentration gradients are all _________
Carrier proteins
Sodium-potassium pump
Exchanges Na+ for K+ across the plasma membrane of animal cells.
All cells have voltages across their plasma membrane
True
Voltage
Electric potential energy
Membrane potential
The voltage across a membrane
Ranges from about -50 to -200 millivolts (mV)
The cytoplasmic side of the membrane is negative in charge relative to the extracellular side
True
The membrane potential favors the passive transport of cations into the cell and anions out of the cell because the inside of the cell is negative compared with the outside
True
Two forces drive the diffusion of ions across a membrane
A chemical force (the ion’s concentration gradient)
An electrical force (the effect of the membrane potential on the ion’s movement)
Electrochemical gradient
The combination of forces acting on an ion
An ion diffuses down its …
Electrochemical gradient
Electrogenic pump
A transport protein that generates voltage across a membrane
Proton pump
-electrogenic pump
Actively transports protons (H+) out of the cell.
Exocytosis
The process where the cell secretes certain molecules by the fusion of vesicles with the plasma membrane
In endocytosis,
The cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane.
Three types of endocytosis
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis
Ligands
A term for any molecule that binds specifically to a receptor site on another molecule
