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21 Cards in this Set

  • Front
  • Back
3 Means of Intercellular Communication
1. gap junction
2. direct signaling
3. extracellular chemical messengers
Define gap junction.
def. communicating junctions that permit the passage of small molecules
Define direct signaling.
def. extracellular protein-protein interactions
Types of extracellular chemical messengers.
1. paracrine - local, no
electrical signal involved
2. hormone - global, through
bloodstream, no electrical
signal involved
3. neurotransmitter - local,
electrical singal involved
4. neurohormone - global,
electrical signal involved
How are extracellular chemicals secreted by one cell detected by another?
1. G protein coupled receptors, coupled to 2nd messenger pathway
- e.g. cAMP, IP3 pathway
- ultimately bring about a
cellular response by
altering the structure
and function proteins

2. Activation of ion channels
- 2 major type:
a. leak channels -
always open
b. gated channels -
open and close in
response to
various stimuli;
2 types
2 types of signaling for gated channel
1. ionotropic signaling-
activation of ion
channels by direct
binding of extracellular
chemical messenger
2. metabotropic signaling-
activation of ion channel
2nd messenger pathway
Define Membrane Transport.
def. the movement of substances across the PM for the purpose of homeostasis or carrying out of specific fncs
- the PM is selectively permeable to some certain substance; therefore some must be actively transported while other passively diffuse
Define passive transport.
def. substances which can permeate the PM can freely diffuse through it w/o the expenditure of cellular energy.
- this type of transport occur through movement along an electrical or chemical gradient or by carrier mediated mechanisms.
Define active transport.
def. movement across the PM that requires cellular energy expenditure
- this type of transport occurs for substances going against their electrochemical gradient or is impermeable to the PM
- 2 types of active transport
2 types of active transport
1. membrane pump
2. vesicular transport
Unassisted Membrane Transport Occurs via Two Mechanism:
1. Diffusion down a
concentration gradient -
random movment of
molecules from regions of
high conc. to regions of
low conc.
2. movement along an electrical gradient -
molecules that are
electrically change will
move in the direction
along an electrical
gradient that is
determined by their
Define Electricalchemical gradient
def. the combined force of concentration and electrical gradients that act on molecular and ionic substances
Factors affecting the rate of diffusion through a membrane:
1. magnitude of the concentration gradient
2. permeability of the membrane
3. S.A. of the membrane
4. distance over which diffusion takes place
Define Osmosis.
def. a special case of passive transport occurring when water diffuses down its concentration gradient to regions of higher solute concentration.
Define osmotic pressure.
def. the magnitude of the opposing hydrosttic pressure that is necessary to stop osmosis.
- when hydrostic pressure = osmotic pressure, equilibrium occurs
Define carrier mediated transport
def. this process occurs when a substance is bound to a transmembrane protein that undergoes a conformational change and the substance is released on the the other side of the membrane
Define Faciliated Diffusion.
def. The binding of the substance can directly cause the protein (CARRIER) to change its conformation (SHAPE, CONFIGURATION) and thereby facilitate its diffusion across the membrane (Figure 3-15), or the conformational change can be induced by a separate process, such as phosphorylation, that causes the protein to undergo an energy-dependent conformational change
Function of Membrane Pumps
- active transport of one or more ionic species against their electrochemical gradients. Examples include the hydrogen-ion pump and the Na+/K+ ATPase.
Function of Hydrogen-Ion Pump
active transport protein that moves H+ against its concentration gradient.
Function of Na+/K+ ATPase
def. Active transport protein that transports Na+ out of the cell and K+ into the cell .
Three Na+ ions are transported out for every two K+ ions in (Figure 3-22; 3-18).
This pump is present in every cell and has 3 main functions:
maintenance of Na+ and K+ concentration gradients
maintenance of osmotic balance
establishment of energy gradients are used for co-transport of other substances
Define vesicular transport.
def. The movement of large polar molecules or macromolecules across the plasma membrane by means of endocytosis and exocytosis.