Cell Membrane, Membrane Transport and Membrane Potential Flashcards
structural proteins form
cell to cell attachments that hold adjacent epithelial cells together
structural proteins sometimes anchors
cells to ECM
tight junctions
prevents intercellular movement of fluid and dissolved substances
desmosomes
structural support
gap junctions
cell to cell communication via ions
enzymes
integral membrane, transmembrane, or peripheral membrane proteins that catalyze specific chemical reactions either on the extracellular surface of cell oe inside cell
properties of enzymes (3)
specificity
saturation
competition
how long does it take to synthesize proteins
2 hours
when are most proteins synthesized?
in advance and stored in an inactive form, activated when needed
proteins provide a means for
immediate protein regulation
interaction between substance and protein binding site follows the
mass action model
glycococalyx
attached to EC surface of membrane lipids and proteins
glycocalyx plays an important role in
enabling cells to identify and interact with each other
characteristics of membrane structure (4)
selectively permeable barrier
mosaic
dynamic
fluid
which concentrations are higher outside of the cell (5)
Na+ Ca++ Cl- HCO3- Glucose
which concentrations are higher inside the cell (6)
K+ Mg++ Phosphates Animo acids pH Proteins
passive transport (3)
no energy required
down gradients (high to low; deltaC, deltaP, or deltaE)
diffusion, osmosis, bulk flow
active transport (3)
energy required
up gradients (low to high)
active transporters, bulk (vesicular) transport
random thermal motion
molecules in a fluid are continuously and randomly bouncing around
rate of movement is proportional to
(temp)/(mass)
diffusion
movement of substances other than water down a gradient (deltaC; deltaE or deltaP; how to low)
net movement stops at
equilibrium
random movement is
continuous
diffusion is — specific
substance
passive transport moves the system towards
equilibrium
mass and heat flow model
concentration gradient (higher energy, lower energy)
driving force
mass or energy flow
resistance
what can the mass and heat flow model be used to describe? (5)
diffusion osmosis blood flow through blood vessels air flow through airways capillary exchange
type of substances
simple diffusion:
facilitated diffusion:
hydrophobic/lipophilic substances
hydrophilic/lipophobic substances
movement
simple diffusion:
facilitated diffusion:
move directly through phospholipid bilayer
require membrane channels or carriers
speed
simple diffusion:
facilitated diffusion:
slower
faster
regulation
simple diffusion:
facilitated diffusion:
unregulated
regulated (specificity, saturation, competition)
plasma membrane?
simple diffusion:
facilitated diffusion:
does not require
requires
simple diffusion rate (SDR) equation
((gradient)(temp)(surface area))/((resistance)(diffusion distance))
facilitated diffusion rate (FDR) IONS equation
(gradient)(temp)(#channels)(probability channels are open)
facilitated diffusion rate (FDR) MOLECULES equation
(gradient)(temp)(#carriers)
why are the kinetics of simple and facilitated diffusion different?
facilitated diffusion results in saturated carriers, would need more carriers to to increase rate of diffusion
osmosis
movement of water across a plasma membrane down a free [h2o] gradient
water movement via osmosis is facilitated by
awuaporins
water permeability can be
regulated
[free h2o] is proportional to
1/[solute]
how will water molecules move?
passively down a free water gradient (toward the area with a higher solute concentration)
which 3 values change during osmosis?
solute conc
water conc
container volume
is osmosis substance specific?
no
what determines h2o movement via osmosis?
impermeable substances
osmolarity
the total (free) solute concentration of a solution (permeable and impermeable)
one osmol is equal to
1 mol of solute particles
a 1M solution of glucose has a concentration of —, whereas a 1 M solution of NaCl is —
1 Osm (1 osmol/L)
2 Osm (2 Osm of solute/1 L of solution)
isosmotic
bathing solution Osm=cytosolic Osm
hyposmotic
bathing solution Osm
hyperosmotic
bathing solution Osm>cytosolic Osm
tonicity
defined by the number of impermeable substances only
tonicity determines the
direction of h2o movement via osmosis
bc only impermeable substances determine the movement
isotonic solution (2)
concentration of impermeable substance=cell cytosol
cells in an isotonic bathing solution will have no net change in volume
hypotonic solutions (2)
concentration of impermeable substance
hypertonic solutions (2)
concentration of impermeable substance>cell cytosol
cells in an isotonic bathing solution will lose water and shrink
normal ECF is – mosm of nonpenetrating solute
300
normal cytosol is – mosm of nonpenetrating solute
300
under normal circumstances, ECF Osm, is — to cell cytosol
isotonic
cells do not have a net change in
volume
what exists to maintain ECF Osm. isotonic?
homeostatic processes
pressure is required to – the flow of water into a compartment
stop
permeable solutes (7)
ethanol FA O2 CO2 steroids urea glucose (dextrose)
impermeable solutes (6)
Na+ K+ Cl- CHO3- protein others
any given cell, at any given moment may or may not be permeable to
glucose or urea
any given cell, at any given moment may or may not be permeable to glucose or urea. this depends on (2)
cell type (ex. RBC always permeable to urea/glucose)
chemical signals present at the time (ex. liver and muscle cells only permeable to glucose if insulin present)
if asked about a single cell and cell identity is not provided, assume
glucose and urea may be impermeable
if asked about whole water over time, assume
glucose and urea are permeable
how abundant is water in the body
most abundance molecule, accounts for 60% of body weight
think about water as either
intracellular or extracellular
the volume of water in the intracellular vs extracellular spaces is
unequal
the osmolarity of the extracellular and intracellular spaces is
equal
blood plasma accounts for
5% ECF
interstitial fluid accounts for
15% ECF
intracellular fluid accounts for
40%
active transport requiers an
input of energy
two types of active transport
- active transport with membrane proteins (typically what is meant)
- bulk (vesicular) transport
active transporters
transmembrane protein that moves ions and hydrophilic building blocks across the plasma membrane up a deltaC (requires energy)
classification of active transporters is based on (3)
- number of substances being transported
- directions substances are transported
- source of energy for transport
types of active transporters are based on (2)
number and direction of movement
uniporter
moves only one substance
symptorters/cotransporters
all substances moving in same directions
antiporter/countertransporter
substances moving in different directions
primary active transporters
energy comes directly from breakdown of ATP
secondary active transporters
energy released from one substance moving down a gradient is used to pump a second substance up a gradient
examples of active transport (3)
sodium potassium pump
calcium pump
hydrogen pump
sodium potassium pump functions (2)
maintain Na+ and K+ concentration differences
electrogenic- establishes negative membrane potential
cotransporteres (symporters) examples (2)
Na/glucose symporter
Na/aa symptorter
countertransporters (antiporters) ex
Na/Ca exchanger
Through a H+ channel (diffusion; DOWN concentration gradient), H+ moves
outside of
the cell
However, if H+ is moving via active transport
(against its concentration gradient), then it will be moving
into the cell
What type of H+ transporter is found in the
apical epithelium of the stomach??
vesicular transport/bulk transport
moves large substances across the PM
vesicular transport/bulk transport is — dependent
gradient
vesicular transport/bulk transport requires
energy
two types of vesicular transport/bulk transport
endocytosis
exocytosis
endocytosis (3)
brings substances into cell
forms vesicle
removes membrane from PM
exocytosis (3)
removes substances from cell
vesicle fuses to membrane
adds membrane to PM
vesicular transport/bulk transport is how the cell modifies….
composition of the PM
membrane potentials (Vm)
charge difference across the PM
membrane potentials (Vm) is created by
unequal distribution of anions and cations across the cell membrane
charge separation =
source of energy
resting membrane potential
the charge difference across the plasma membrane when the cell us ate rest
normal resting Vm
!-70mV (varies by cell type)
– represents the charge inside the cell
sign
membrane potential creates the electrical gradients for
movement of ions into/out of cells
membrane potential opens or closes
gated ion channels
membrane potential regulates
exocytosis
