Chapter 7 Flashcards
amphipathic
has both a hydrophilic (water loving) region and a hydrophobic (water fearing) region
fluid mosaic model
accepted model of a cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids
cholesterol within the cell membrane
reduces membrane fluidity at moderate temperatures by reducing phospholipid movement, but at low temperatures it hinders solidification by disrupting the regular packing of phospholipids
unsaturated hydrocarbon tails
kinked, prevent packing, enhancing membrane fluidity
saturated hydrocarbon tails
pack together, increasing membrane viscosity
integral proteins
penetrate the hydrophobic interior of the liquid bilayer
transmembrane proteins
span the membrane
peripheral proteins
are not embedded in the lipid bilayer at all, loosely bound to the surface of the membrane
functions of membrane proteins
transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to the cytoskeleton and extracellular matrix
glycolipid
a lipid with one or more covalently attached carbohydrates
glycoproteins
a protein with one or more covalently attached carbohydrates
selective permeability
the membrane allows some substances to cross more easily than others; non polar, hydrophobic molecules (like hydrocarbons, CO2, O2) can cross the lipid bilayer easily; polar, hydrophilic molecules (like sugars water, charged molecules) cross the lipid bilayer slowly
transport proteins
a transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane
aquaporins
channel proteins that allow water to cross a lipid bilayer
diffusion
movement of particles of any substance so that they spread out into available space
concentration gradient
a region along which the density of a chemical substance increases or decreases
passive transport
diffusion of a substance across a biological membrane without requiring energy
osmosis
the diffusion of water across a selectively permeable membrane
tonicity
the ability of a surrounding solution to cause a cell to gain or lose water
isotonic
no net movement of water across the plasma membrane; makes animal cells normal and plant cells flaccid
hypertonic
referring to a solution that when surrounding a cell will cause the cell to lose water; makes animal cells shriveled and plant cells plasmolyzed
hypotonic
referring to a solution that when surrounding a cell will cause the cell to take up water; makes animal cells lysed and plant cells turgid (normal)
osmoregulation
the control of solute concentrations and water balance
facilitated diffusion
the passage of molecules or ions down the electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure
ion channels
channel proteins that transport ions
gated channels
open or close in response to a stimulus
active transport
pumps a solute across a membrane against its concentration gradient, requiring energy
sodium-potassium pump
a transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell
membrane potential
the difference in electrical charge (voltage) across a cell’s plasma membrane due to the differential distribution of ions, affects the activity of excitable cells and the transmembrane movement of all charged substances
electrochemical gradient
the diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (chem force) and the ion’s tendency to move relative to the membrane potential (elec force)
electrogenic pump
a transport protein that generates voltage across a membrane; main one of plants, fungi, and bacteria is the proton pump
cotransport
the coupling of the downhill diffusion of one substance to the uphill transport of another against its own concentration gradient
exocytosis
the cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane
endocytosis
cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane
