Npb_Membrane Transport

Front 1

3 Means of Intercellular Communication

Back 1

1. gap junction
2. direct signaling
3. extracellular chemical messengers

Front 2

Define gap junction.

Back 2

def. communicating junctions that permit the passage of small molecules

Front 3

Define direct signaling.

Back 3

def. extracellular protein-protein interactions

Front 4

Types of extracellular chemical messengers.

Back 4

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

Front 5

How are extracellular chemicals secreted by one cell detected by another?

Back 5

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
i/ionotropic
signalizing
ii/metabotropic
signaling

Front 6

2 types of signaling for gated channel

Back 6

1. ionotropic signaling-
activation of ion
channels by direct
binding of extracellular
chemical messenger
2. metabotropic signaling-
activation of ion channel
2nd messenger pathway

Front 7

Define Membrane Transport.

Back 7

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

Front 8

Define passive transport.

Back 8

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.

Front 9

Define active transport.

Back 9

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

Front 10

2 types of active transport

Back 10

1. membrane pump
2. vesicular transport

Front 11

Unassisted Membrane Transport Occurs via Two Mechanism:

Back 11

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
polarity

Front 12

Define Electricalchemical gradient

Back 12

def. the combined force of concentration and electrical gradients that act on molecular and ionic substances

Front 13

Factors affecting the rate of diffusion through a membrane:

Back 13

1. magnitude of the concentration gradient
2. permeability of the membrane
3. S.A. of the membrane
4. distance over which diffusion takes place

Front 14

Define Osmosis.

Back 14

def. a special case of passive transport occurring when water diffuses down its concentration gradient to regions of higher solute concentration.

Front 15

Define osmotic pressure.

Back 15

def. the magnitude of the opposing hydrosttic pressure that is necessary to stop osmosis.
- when hydrostic pressure = osmotic pressure, equilibrium occurs

Front 16

Define carrier mediated transport

Back 16

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

Front 17

Define Faciliated Diffusion.

Back 17

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

Front 18

Function of Membrane Pumps

Back 18

- active transport of one or more ionic species against their electrochemical gradients. Examples include the hydrogen-ion pump and the Na+/K+ ATPase.

Front 19

Function of Hydrogen-Ion Pump

Back 19

active transport protein that moves H+ against its concentration gradient.

Front 20

Function of Na+/K+ ATPase

Back 20

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

Front 21

Define vesicular transport.

Back 21

def. The movement of large polar molecules or macromolecules across the plasma membrane by means of endocytosis and exocytosis.