Chapter 6 Flashcards
a membrane with 2 molecular layers
bilayer
the predominant sterol of animal cell membranes
cholesterol
a protein embedded in the cell membrane that forms a channel allowing selected polar molecules and ions to pass across the membrane
transport proteins
protein in the plasma membrane that identifies a cell as part of the same individual or as foreign
recognition proteins
protein that recognizes and binds molecules from other cells that act as chemical signals
receptor proteins
protein that binds cells together by recognizing and binding receptors or chemical groups on other cells or on the extracellular matrix
cell adhesion proteins
a lipid molecule with carbohydrate groups attached
glycolipids
protein with carbohydrate groups attached
glycoproteins
a carbohydrate coat covering the cell surface
glycocalyx
model proposing that the membrane consists of a fluid phospholipid bilayer in which proteins are embedded and float freely
fluid mosaic model
protein embedded in a phospholipid bilayer
integral proteins
protein held to membrane surfaces by noncovalent bonds formed with the polar parts of integral membrane proteins or membrane lipids
peripheral proteins
technique in which experimenters freeze a block of cells rapidly, then fracture the block to split the lipid bilayer and expose the hydrophobic membrane interior
freeze-fracture technique
the controlled movement of ions and molecules from one side of a membrane to the other
transport
the transport of substances across cell membranes without expenditure of energy, as in diffusion
passive transport
the mechanisms by which ions and molecules move against the concentration gradient across a membrane from the side with the lower concentration to the side with the higher concentration
active transport
the net movement of ions or molecules from a region of higher concentration to a region of lower concentration
diffusion
a difference in concentration molecules or ions between 2 areas
concentration gradient
membranes that selectively allow, impede, or block the passage of atoms and molecules
selectively permeable
mechanism by which certain small substances diffuse through the lipid part of a biological membrane
simple diffusion
mechanism by which polar and charged molecules diffuse across membranes with the help of transport proteins
facilitated diffusion
transport protein that forms a hydrophilic channel in a cell membrane through which water, ions, or other molecules can pass, depending on the protein
channel proteins
a specialized protein channel that facilitates diffusion of water through cell membranes
aquaporins
ion transporter in a membrane that switches between open, closed, or intermediate states
gated channels
transport protein that binds a specific single solute and transports it across the lipid bilayer
carrier proteins
the passive transport of water across a selectively permeable membrane in response to solute concentration gradients, a pressure gradient, or both
osmosis
a state of dynamic equilibrium in which the pressure of the solution on one side of a selectively permeable membrane exactly balances the tendency of water molecules to diffuse passively from the other side of the membrane due to a concentration gradient
osmotic pressure
the effect a solution has on a cell when the solution surrounds it
tonicity
solution containing dissolved substances at lower concentrations than the cells it surrounds
hypotonic
the internal hydrostatic pressure within plant cells
turgor pressure
solution containing dissolved substances at higher concentrations than the cells it surrounds
hypertonic
conditions due to outward osmotic movement of water, in which plant cells shrink so much that they retract from their water
plasmolysis
equal concentration of water inside and outside cells
isotonic
the mechanism by which ions and molecules move against the concentration gradient across a membrane, from the side with the lower concentration to the side with the higher concentration
active transport
an electrical voltage that measures the potential inside a cell membrane relative to the fluid just outside; it is negative under resting conditions and becomes positive during an action potential
membrane potential
transport in which the same protein that transports a substance also hydrolyzes ATP to power the transport directly
primary active transport
transport indirectly driven by ATP hydrolysis
secondary active transport
pump that moves hydrogen ions across membrane and pushes hydrogen ions across the plasma membrane from the cytoplasm to the cell exterior
proton pumps/ H+ pump
pump that pushes Ca2+ from the cytoplasm to the cell exterior, and also from the cytosol into the vesicles of the endoplasmic
Ca2+ pump
pump that pushes 3 Na+ out of the cell and 2 K+ into the cell in the same pumping cycle
Na+/K+ pump
a difference in chemical concentration and electric potential across a membrane
electrochemical gradient
the transport of 2 molecules in the same direction across a membrane
symport
a secondary active transport mechanism in which a molecule moves through a membrane channel into a cell and powers the active transport of a second molecule out of the cell
antiport/exchange diffusion
mechanism by which extracellular water is taken into a cell together with any molecules that happen to be in solution in the water
bulk-phase endocytosis
the selective uptake of macromolecules that bind to cell surface receptors concentrated in clathrin-coated pits
receptor-mediated endocytosis
a depression in the plasma membrane that contains receptors for macromolecules to be taken up by endocytosis
coated pit
the network of proteins that coat and reinforce the cytoplamic surface of cell membranes
clathrin
process in which some types of cells engulf bacteria or other cellular debris to break them down
phagocytosis
the outer limit of the cytoplasm responsible for the regulation of substances moving into and out of cells
plasma membrane
