AP Bio Ch. 7
Terms in this set (60)
The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids
Having both a hydrophilic region and a hydrophobic region
A transmembrane protein with hydrophobic regions that extend into and often completely span the (hydrophobic) interior of the membrane. Can also be found with hydrophobic regions that are in contact with the aqueous solution on one or both sides of the membrane (or lining the channel, if it is a channel protein).
A protein loosely bound to the surface of a membrane or to part of an integral protein. These are not embedded in the lipid bilayer.
A protein with one or more covalently attached carbohydrates
A lipid with one or more covalently attached carbohydrates
A property of biological membranes that allows them to regulate the passage of substances across them
A transport protein that helps a certain substance Orr class of closely related substances to cross the membrane
A channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis.
The spontaneous movement of a substance down its concentration or electrochemical gradient, from a region where it is more concentrated to a region where it's less concentrated
A region along which the density of a chemical substance increases or decreases
Diffusion of free water across a selectively permeable membrane
The ability of a solution surrounding a cell to cause that cell to gain or lose water
Referring to a solution that, when around the cell, will cause the cell to lose water
Referring to a solution that, when around a cell, will cause the cell to take in water
Referring to a solution that causes no net movement of water in or out of the cell
Swollen or distended, as in plant cells (happens if plant cell has less water inside than outside)
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall, occurs when the cell lose water to a hypertonic environment
Regulation of solute concentration and water balance by a cell or organism
The diffusion of a substance across a biological membrane with no loss of energy
The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure
a transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration gradient OR electrochemical gradient.
a transmembrane protein channel that opens or closes in response to a particular stimulus
movement of substance across a cell membrane AGAINST its concentration gradient, therefore requiring cell energy in the form of ATP.
This movement is controlled by specific transport proteins
A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell
the difference in electrical charge (voltage) across a cell's plasma membrane due to the differential distribution of ions.
This affects the activity of excitable cells and transmembrane movement of all charged substances
diffusion gradient of an ion, which is affected by both the
- concentration difference of an ion across a membrane (a chemical force)
- ion's tendency to move relative to membrane's potential (electrical force)
active transport proteins that generate voltage across a membrane while pumping ions
active transport proteins in a cell membrane that use ATP to transport hydrogen ions (H+, which are protons)out of a cell against their concentration gradient
this generates a membrane potential
the coupling of a "downhill" diffusion of one substance to the "uphill" movement of another substance against its own concentration gradient
the cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane
molecules that bind specifically to another molecule, usually a larger one.
Popular in receptor-mediated endocytosis
cellular uptake of biological molecules and particular matter by means of forming vesicles from the plasma membrane
type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It's carried out by some protists and by certain immune cells of animals.
a type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes
movement of specific molcules into a cell by the inward budding of vesicles that have proteins with receptor sites specific to the molecules (ligands) being taken in
enables a cell to get bulk quantities of specific substances
6 jobs of proteins
- transport of specific solutes
- receptor - relaying a message (from ligands, protein hormones, etc)
- cell to cell recognition: grouping of cells/identifying cells
- intercellular joining: gap or tight junction
- attachment: to ECM or cytoskeleton
Why are phospholipids amphipathic models?
they have a hydrophilic head and 2 hydrophobic fatty acid tails
describe the fluidity of components of a cell membrane and explain how membrane fluidity is influenced by temperature and membrane composition
- the components help to determine fluidity: unsaturated fatty acids have kinks which allow for fluidity/spacing; saturated fatty acids are more tightly packed
- temperature & composition: the components of the membrane help prevent the temperature around the cell from impacting the cell in a negative way.
- too hot: membrane could get too liquid-y and could not hold stuff in
- too cold: membrane could get too solid and would not be able to bring substances/particles in
explain how cholesterol resists changes in membrane fluidity with temperature change
cholesterol helps hold the membrane together, but not too tightly.
cholesterol is embedded in the membrane and helps keep good spacing (prevents solid-ness)
what is the difference between peripheral and integral membrane proteins?
- peripheral: not embedded in membrane but is on edges/outside of it
- integral: embedded in the membrane/inside it
explain role of membrane carbs in cell-cell recognition
carbohydrates (usually attached to proteins or lipids) act as markers on the cell surface to identify the cell as part of a particular group
- example: blood groups (each diff type of blood cell has special markers on outside)
what is the difference between channel proteins and carrier proteins?
- channel proteins: hydrophilic channel that certain molecules/ions can use as a channel through the membrane. Aquaporins are channel proteins
- carrier proteins: bind to molecules and change shape to shuffle molecules across membrane. Glucose pump, sodium/potassium (sump) pump
BOTH ARE TYPES OF TRANSPORT PROTEIN!
how do hydrophobic molecules cross cell membranes?
why is diffusion a spontaneous process?
contrast hypertonic, hypotonic, and isotonic solutions
- hypertonic: solutions that have less water than the other solution/cell that's in them, so this solution will draw water out of the cell/substance, causing the cell to shrivel/maybe die
- hypotonic (hypO=explOde):solutions that have more water than the cell inside them, so the cell will gain water, swell, and burst.
- isotonic: solution has roughly equal concentration of water, so there is no net movement of water across plasma membrane of cell inside the solution. Water moves across membrane, but at same rate in both directions.
how do animal cells and plant cells differ in their reactions to the tonicity of solutions?
- animal cells like isotonic solutions the best. If in hypotonic solution, cell takes in too much water and can burst. If in hypertonic solution, too much water is leaving the cell and the cell can shrivel and die.
- plant cells like hypotonic solutions the best because the cell has taken up as much water as it poss. can and its walls keep excess water from coming in. Turgid = terrific. Isotonic causes cell to become flaccid, causing wilting. If in hypertonic solution, plant will lose water and volume shrinks and plasmolysis can occur.
predict the direction of water movement during osmosis based on differences in solute concentrations (if there is ___ type of solution, where will the water go?)
- osmosis moves water from an area of high concentration to an area of low concentration.
- hypotonic: water coming into cell
- hypertonic: water leaving cell
- isotonic: no
explain how transport proteins facilitate diffusion
Osmosis notes (details)
- movement of water,
- moves water from high to low concentration,
- uses aquaporin protein,
- passive transport, no energy needed
- movement of ions, glucose, amino acids,
- moves stuff from high to low concentration,
- uses channel protein,
- passive transport, no energy needed
- movement of proteins (via protein pumps) or bulk objects (endo/exo-cytosis)
- protein pumps move proteins from a low to high concentration. Endocytosis brings things into cell, exo removes things from cell
- uses pumps or vesicles formed from cell membrane
- energy needed in form of ATP
What is cotransport, and what is the process of cotransport?
cotransport is a form of diffusion -- "downhill" diffusion of one substance combined with "uphill" diffusion of another substance that runs counter to the concentration gradient of the first substance.
- process: a proton pump works with another transport protein. While the pump transports one solute, it can indirectly drive the active transport of other solute(s).
how are large molecules transported across a cell membrane?
- through either exocytosis or endocytosis, processes in which vesicles mesh with the cell membrane and can pass through the lipid bilayer
- large molecules: polysaccharides and proteins
what is the difference between pinocytosis and receptor-mediated endocytosis?
- pinocytosis: "drinking" - takes in drops of extracellular fluid in order to obtain the molecules within the fluid.
- receptor-mediated: only certain material types because the receptors it uses
the types of passive transport
simple diffusion, facilitated diffusion, osmosis
the types of active transport
protein pumps, endocytosis, exocytosis
types of active transport pumps
proton (which help with cotransport) and sodium-potassium
types of facilitated diffusion
channel (includes osmosis) and carrier
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