Cell Signaling Flashcards
mass balance in the body
mass balance= existing body load + intake or metabolic production - excretion or metabolic removal
clearance
rate at which a molecule disappears from teh body
mass flow=
concentration x volume flow
homeostasis and equilibrium relationship
not equal to one another
three types of equilibrium
-chemical disequilibrium
-electrical disequilibrium
-osmotic equilibrium
three body fluid compartments
plasma
interstitial fluid
intracellular fluid
what portion of the plasma membrane is highly permeable to nonpolar molecules?
lipid bilayer
the lipid bilayer is moderately permeable to
small, uncharged polar molcules
the lipid bilayer is impermeable to
ions and large, uncharged polar molecules
concentration gradient
is a difference in the concentration of a chemical from one place to another
an electrical gradient is a
difference in electrical charges between 2 regions
electrochemical gradient
refers to the combined influence of the concentration gradient and the electrical gradient on movement of a particualr ion across a membrane
K+ wants to be
inside the cell
active transport
requires energy
primary active transport is
the direct phosphorylation of ATP
secondary active transport
utilizes conditions based on secondary factors
-does not involve direct phosphorylation of atp
seven properties of diffusion
- passive process (obeying second law of thermodynamics)
- high concentration to low concentration
- net movement until concentration is equal
- rapid over short distances
- directly related to temperature
- inversely related to molecular size
- in open system or across a partition
diffusion (obeying second law of thermodynamics)
movement of a substance down its concentration gradient due to its kinetic energy
fick’s law of diffusion
rate of diffusion is directly proportional to surface area, concentration gradient, membrane permeability
indirectly proportional to membrane thickness
membrane thickness is based on
lipid solubility / molecular size
changing the composition of the lipid layer can
increase or decrease membrane permeability
a larger size molecule will ___ membrane permeability
decrease
diffusion across a membrane
simple and facilitated
simple diffusion
a solute moves across the lipid bilayer of the plasma membrane without the help of membrane transport proteins
facilitated diffusion
a solute moves across the lipid bilayer aided by a channel protein or a carrier protein
channel-mediated facilitated diffusion
gated channel
gated channel is
one in which a portion of the channel protein acts as a gate to pen or close the channel’s pore to the passage of ions
carrier-mediated facilitated diffusion
carrier protein
solute specificity
carrier protein binds to
a substance on one side of the membrane, undergoes a conformational change, and then releases the substance on the opposite side of the membrane
solute specificity (somewhat)
a given carrier protein transports only one solute or a group of solutes that are structurally related
properties of carrier proteins
saturation
competition (for related compounds)
glucose binds to a specific type of carrier protein called the
glucose transporter (glut). the binding site initially faces the outside surface of the membrane
the transporter undergoes a conformational change which causes
the binding site to face the inside of the cell
glucose dissociates from the
transporter and enters the cytosol
channel proteins
create a water-filled pore
channel proteins can be classified as
gated channels and open channels
carrier proteins
never form an open channel between the two sides of the membrane
carrier proteins can be classified as
uniport carriers
cotransporters
-symport carriers
-antiport carriers
the sodium potassium pump expels
sodium ions and brings potassium ions into the cell. note: k+ electrical and concentration gradients occur in opposite directions (high to low)
secondary active transport mechanisms use
the energy stored in an ionic electrochemical gradient (usually Na+)
because primary active transport pumps the hydrolyzed ATP to maintain the gradient, secondary active transport mechanisms consume ATP indirectly
both AT use energy
symporters
carry two substances across the membrane in the same direction
antiporters
carry two substances across the membrane in opposite directions
Na+ is moving ___ its electrochemical gradient
down
osmosis is
the diffusion of water
the body is mostly water
most water volume in intracellular
extracellular
plasma
principle of osmosis based off of
solute concentrations
osmolarity of a solution is a measure of the
total number of dissolved particles per liter of solution. the particles may be molecules, ions, or a mixture of both
isoosmotic
same osmolarity as another solution
hyperosmotic
higher osmolarity than another solution
hypoosmotic
lower osmolarity than another solution
tonicity
tonic= tension
measure of a solution’s ability to change the volume of cells by altering their water content
in a hypotonic solution
the cell swells
in a hypertonic solution
the cell shrinks
tonicity depends on the relative concentrations of
nonpenetrating solutes
tonicity only depends on
nonpenetrating solutes
intravenous solutions
fluid therapy is dependent on
osmolarity and tonicity
hypotonic solutions are used in conditions of
dehydration
isotonic solutions are used in
blood loss, fluid is needed to remain in the ECF (interstitial + plasma)
cell to cell communication overview (3)
- physiological communication signals
- target cells, or targets, receive signals
- 3 general methods of cell-to-cell communication
physiological communication signals
electrical
chemical
electrical
changes in the membrane potential of a cell
chemical
secreted by cells into ECF
responsible for most communication within the body
cells can communicate with one another through
gap junctions
cell to cell binding
extracellular chemical messengers
process of extracellular chemical messengers
- binding of the extracellular chemical messenger to a receptor
- signal transduction
- cellular response
binding of the extracellular chemical messenger to a receptor
the receptor may be present in the target cell’s plasma membrane or inside the target cell
signal transduction
sequence of events that occurs during signal transduction is referred to as a signal transudction pathway
cellular response
signal transduction pathway culminates in a cellular response by the target cell
3 major types of extracellular chemical messengers
- hormones
- neurotransmitters
- local mediators
hormones
mediate endocrine signaling
neurotransmitters
mediate synaptic signaling
local mediators
paracrines and autocrines
mediate local signaling
lipophobic bind to
membrane of cell
lipophilic
signal molecules and go in cell or bind to cell membrane
steroid
lipophilic have ____response
slower while lipophobic is more rapid
signal pathways: signal amplification
transducers
convert extracellular signals into intracellular messages which create a response
steps of signal transduction pathway form a
cascade
modulation of signal pathways
-specificity and competition
-agonist versus antagonist
-multiple receptors for one ligand (e.g. epinephrine)
alpha receptor
vasconstriction
beta receptor
vasodilation
antagonist
blocks receptor activity while an agonist activates the receptor for a response
the target response depends on the
target receptor
other modulation of signal pathway
up regulation
down regulation
termination mechanism
disease and drugs
down-regulation
-by decreasing the number of receptors
-by decreasing the binding affinity
-one explanation for drug tolerance
physiological control systems keep
regulated variables within a desired range during homeostasis
control systems: cannon’s postulates
- nervous regulation of internal environment
- tonic control
- antagonistic control (e.g. insulin and glucagon)
- one chemical signal can have different effects in different tissues (epinephrine)
tonic control regulates physiological parameters in an
up-down fashion
antagonistic neurons control
heart rate: some speed it up, while others slow it down
stimulation by ___ nerves increases heart rate
stimulation by ____ nerves decreases heart rate
sympathetic
parasympathetic
control pathways: setpoints
oscillation around the setpoint
acclimatization refers to
natural adaptation
acclimation refers to
induced adaptation
feedforward control refers to
anticipatory responses
the response counteracts the stimulus, shutting off the response loop
