Chapter 5 Vocab Flashcards
a property of biological membranes that allows them to regulate the passage of substances across them
selective permeability
having both a hydrophilic region and a hydrophobic region
amphipathic
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.
fluid mosaic model
a transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane (or lining the channel in the case of a channel protein).
integral protein
a protein loosely bound to surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer
peripheral protein
a lipid with one or more covalently attached carbohydrates
glycolipid
a protein with one or more covalently attached carbohydrates
glycoprotein
a transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane
transport protein
a channel protein in the plasma membrane of a plant, animal or microorganism cell that specifically facilitates osmosis, the diffusion of free water across the membrane
aquaporin
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 is less concentrated.
diffusion
a region along which the density of a chemical substance increases or decreases.
concentration gradient
the diffusion of a substance across a biological membrane with no expenditure of energy
passive transport
the diffusion of free water across a selectively permeable membrane
osmosis
the ability of a solution surrounding a cell to cause that cell to gain or loose water.
tonicity
referring to a soultion that, when surrounding a cell, causes no net movement of water into or out of a cell
isotonic
referring to a solution that, when surrounding a cell, will cause the cell to lose water
hypertonic
referring to a solution that, when surrounding a cell, will cause the cell to take up water.
hypotonic
regulation of solute concentrations and water balance by a cell or organism
osmoregulation
swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a lower water potential then its surroundings, resulting in entry of water.
turgid
lacking turgor (stiffness or firmness), as in the plant cell in surroundings where there is a tendency for water to leave the cell. ( A wall cell becomes flaccid if it has a higher water potential than its surroundings, resulting in the loss of water.)
flaccid
a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment
plasmolysis
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.
facilitated diffusion
a transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.
ion channels
a transmembrane protein channel that opens or closes in response to a particular stimulus
gated channels
the movement of a substance across a cell membrane against its concentration gradient, mediated by specific transport proteins and requiring an expenditure of energy
active transport
a transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell an potassium into the cell
sodium-potassium pump
the difference in electrical charge (voltage) across a cell’s plasma membrane due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances.
membrane potential
the diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion’s tendency to move relative to the membrane potential (an electrical force).
electrochemical gradient
an active transport protein that generates voltage across a membrane while pumping ions.
electrogenic pump
an active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process
proton pump
the coupling of the “downhill” diffusion of one substance to the “uphill” transport of another against its own concentration gradient
cotransport
the cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.
exocytosis
cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.
endocytosis
molecule that binds specifically to another molecule, usually a larger one.
ligands
a 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.
phagocytosis
a type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes
pinocytosis
the movement of specific molecules into a cell by the inward budding of vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances
receptor-mediated endocytosis
a secreted molecule that influences cells near where it is secreted
local regulators
in multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids and act on specific target cells in other parts of the body, changing target cells functioning. Important in long distance signalling
hormones
the binding of a signaling molecule to a receptor protein, activiating the receptor by causing it to change shape
reception
a process in which phages (viruses) carry bacterial DNA from one bacterial cell to another. When these two cells are members of different species, results in horizontal gene transfer
also
in cellular communication, the conversion of a signal from outside the cell to a form that can bring about a specific cellular response.; also called signal transduction
transduction
a series of steps linking a mechanical, chemical or electrical stimulus to a specific cellular response
signal transduction pathway
1) in cellular communication thechange in specific cellular activity brought about by a transduced signal from outside the cell
2) in feedback regulation a physiological activity triggered by a change in a variable
response
a signal receptor protein in the plasma membrane that responds to the binding of a signaling molecule by activating a G protein.
GPCR
a transmembrane protein containing a pore that opens or closes as it changes shape in response to a signaling molecule (ligand) allowing or blocking the flow of specific ions; also called an ionotrophic receptor
ligand gated ion channel
an enzyme that transfers phosphate groups from ATP to a protein thus phosphorylating the protein
protein kinase
an enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase.
protein phosphatase
a small non-protein water soluable molecule or ion such as a calcium ion (ca2+) or cyclic AMP that relays a signal to a cell’s interior in response to a signaling molecule bound by a signal receptor protein
second messengers
cyclic adenosine monophosphate is a ring shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells. It is also a regulator of some bacterial operons.
cAMP cyclic AMP
