CHAPTER 03: MEMBRANE POTENTIAL Flashcards
active expiration
Emptying of the lungs more completely than when at rest by contracting the expiratory muscles; also called forced expiration
active force
A force that requires expenditure of cellular energy (ATP) in the transport of a substance across the plasma membrane
active transport
Active carrier-mediated transport involving transport of a substance against its concentration gradient across the plasma membrane
adenylyl cyclase
The membrane-bound enzyme that is activated by a G protein intermediary in response to binding of an extracellular messenger with a surface membrane receptor and that in turn activates cyclic AMP, an intracellular second messenger
anion
Negatively charged ion that has gained one or more electrons in its outer shell
apoptosis
Programmed cell death; deliberate selfdestruction of a cell
ATPase
An enzyme that possesses ATP-splitting ability
calmodulin
An intracellular Ca2 binding protein that, on activation by Ca2, induces a change in structure and function of another intracellular protein; especially important in smoothmuscle excitation-contraction coupling
carrier molecules
embrane proteins, which, by undergoing reversible changes in shape so that specific binding sites are alternately exposed at either side of the membrane, are able to bind with and transfer particular substances unable to cross the plasma membrane on their own
carrier-mediated transport
Transport of a substance across the plasma membrane facilitated by a carrier molecule
cascade
A series of sequential reactions that culminates in a final product, such as a clot
cations
Positively charged ions that have lost one or more electrons from their outer shell
caveolae
Cavelike indentations in the outer surface of the plasma membrane that contain an abundance of membrane receptors and serve as important sites for signal transduction
cell adhesion molecules
proteins that protrude from the surface of the plasma membrane and form loops or other appendages that the cells use to grip each other and the surrounding connectivetissue fibers
channels
Small, water-filled passageways through the plasma membrane; formed by membrane proteins that span the membrane and provide highly selective passage for small water-soluble substances such as ions
chemical mediator
A chemical that is secreted by a cell and that influences an activity outside of the cell
chemically gated channels
Channels in the plasma membrane that open or close in response to the binding of a specific chemical messenger with a membrane receptor site that is in close association with the channel
cholesterol
a type of fat molecule that serves as a precursor for steroid hormones and bile salts and is a stabilizing component of the plasma membrane
concentration gradient
A difference in concentration of a particular substance between two adjacent areas
cyclic adenosine monophosphate (cyclic AMP or cAMP)
An intracellular second messenger derived from adenosine triphosphate (ATP)
desmosome (dez+-muh-soxm)
(dez+-muh-soxm) An adhering junction between two adjacent but nontouching cells formed by the extension of filaments between the cellsU plasma membranes; most abundant in tissues that are subject to considerable stretching
diffusion
Random collisions and intermingling of molecules as a result of their continuous thermally induced random motion
electrical gradient
A difference in charge between two adjacent areas
electrochemical gradient
The simultaneous existence of an electrical gradient and concentration (chemical) gradient for a particular ion
endocytosis
Internalization of extracellular material within a cell as a result of the plasma membrane forming a pouch that contains the extracellular material, then sealing at the surface of the pouch to form a small, intracellular, membrane-enclosed vesicle with the contents of the pouch trapped inside
equilibrium potential
The potential that exists when the concentration gradient and opposing electrical gradient for a given ion exactly counterbalance each other so that there is no net movement of the ion
exocytosis
Fusion of a membrane-enclosed intracellular vesicle with the plasma membrane, followed by the opening of the vesicle and the emptying of its contents to the outside
extracellular matrix
An intricate meshwork of fibrous proteins embedded in a watery, gel-like substance; secreted by local cells
facilitated diffusion
Passive carrier-mediated transport involving transport of a substance down its concentration gradient across the plasma membrane
Fick’s law of diffusion
The rate of net diffusion of a substance across a membrane is directly proportional to the substanceUs concentration gradient, the membraneUs permeability to the substance, and the surface area of the membrane and inversely proportional to the substanceUs molecular weight and the diffusion distance
first messenger
An extracellular messenger, such as a hormone, that binds with a surface membrane receptor and activates an intracellular second messenger to carry out the desired cellular response
G protein
A membrane-bound intermediary, which, when activated on binding of an extracellular first messenger to a surface receptor, activates the enzyme adenylyl cyclase on the intracellular side of the membrane in the cAMP second-messenger system
gap junction
A communicating junction formed between adjacent cells by small connecting tunnels that permit passage of charge-carrying ions between the cells so that electrical activity in one cell is spread to the adjacent cell
hormone
A long-distance chemical mediator that is secreted by an endocrine gland into the blood, which transports it to its target cells
hydrogen ion
The cationic portion of a dissociated acid
hypertonic
Having an osmolarity greater than normal body fluids; more concentrated than normal
hypotonic
Having an osmolarity less than normal body fluids; more dilute than normal
impermeable
Prohibiting passage of a particular substance through the plasma membrane
ion
An atom that has gained or lost one or more of its electrons, so that it is not electrically balanced
isotonic
Having an osmolarity equal to normal body fluids
membrane potential
A separation of charges across the membrane; a slight excess of negative charges lined up along the inside of the plasma membrane and separated from a slight excess of positive charges on the outside
Na-K pump
A carrier that actively transports Na out of the cell and K into the cell
net diffusion
The difference between two opposing movements
neurohormones
Hormones released into the blood by neurosecretory neurons
neurotransmitter
The chemical messenger that is released from the axon terminal of a neuron in response to an action potential and influences another neuron or an effector with which the neuron is anatomically linked
osmosis
Movement of water across a membrane down its own concentration gradient toward the area of higher solute concentration
paracrine
A local chemical messenger whose effect is exerted only on neighboring cells in the immediate vicinity of its site of secretion
passive force
A force that does not require expenditure of cellular energy to accomplish transport of a substance across the plasma membrane
permeable
Permitting passage of a particular substance
phosphorylation
Addition of a phosphate group to a molecule
plasma membrane
A protein-studded lipid bilayer that encloses each cell, separating it from the extracellular fluid
primary active transport
A carrier-mediated transport system in which energy is directly required to operate the carrier and move the transported substance against its concentration gradient
protein kinase
An enzyme that phosphorylates and thereby induces a change in the shape and function of a particular intracellular protein
receptor site
Membrane protein that binds with a specific extracellular chemical messenger, thereby bringing about a series of membrane and intracellular events that alter the activity of the particular cell
resting membrane potential
The membrane potential that exists when an excitable cell is not displaying an electrical signal
saturation
When all the binding sites on a carrier molecule are occupied
second messenger
An intracellular chemical that is activated by binding of an extracellular first messenger to a surface receptor site and that triggers a preprogrammed series of biochemical events, which result in altered activity of intracellular proteins to control a particular cellular activity
secondary active transport
A transport mechanism in which a carrier molecule for glucose or an amino acid is driven by a Na concentration gradient established by the energy-dependent Na pump to transfer the glucose or amino acid uphill without directly expending energy to operate the carrier
signal transduction
The sequence of events in which incoming signals (instructions from extracellular chemical messengers such as hormones) are conveyed to the cellUs interior for execution
specificity
Ability of carrier molecules to transport only specific substances across the plasma membrane
state of equilibrium
No net change in a system is occurring
target cell receptors
Receptors located on a target cell that are specific for a particular chemical mediator
target cells
The cells that a particular extracellular chemical messenger, such as a hormone or a neurotransmitter, influences
tight junction
An impermeable junction between two adjacent epithelial cells formed by the sealing together of the cellsU lateral edges near their luminal borders; prevents passage of substances between the cells
transport maximum (Tm)
The maximum rate of a substanceUs carrier-mediated transport across the membrane when the carrier is saturated; known as tubular maximum in the kidney tubules
vesicular transport
Movement of large molecules or multimolecular materials into or out of the cell by means of being enclosed in a vesicle, as in endocytosis or exocytosis
active expiration
Emptying of the lungs more completely than when at rest by contracting the expiratory muscles; also called forced expiration
