L1. Excitable Cells Flashcards
What is the composition of Extracellular fluid “interstitial fluid”
Primarily ions, proteins, and other molecules. Similar to plasma with respect to ionic composition. Therefore, has a high NaCl (high NA and CL).
What are the 3 components of Cell excitation
ECF, intracellular fluid, membrane.
What is the composition of Intracellular fluid “cytosol”
Ions, much higher concentrations of proteins and other molecules. Predominant salt: KCL (k & Cl) so, Inside and outside of cell are very different - this allows cells to communicate
T/F the concentrations of predominant cations (Na vs. K) in the cytosol are the same in the inside and outside of a cell.
False. They’re different.
What does the “membrane” consist of
Phospholipid bilayer and proteins. About equal amounts of protein and lipid, and a small (5%) amount of carbs.
What characteristic is essential to cell excitation?
permeability
The permeability of a membrane to an ion is an index of the ability of the ion _________
to cross the membrane.
Changes in permeability that are ______ and _____, are essential to excitation in cells.
ion-specific and exquisitely timed
During Simple diffusion. Non polar organic molecules diffuse rapidly through the membrane which is 50% _____.
Solubility in lipid is low or high? do you need energy?
50% lipid
is high
no energy
During simple diffusion what do ions cross?
they cross protein channels (several subunits and ion specific) Ex: K channels and Na-Channels.
what are some examples of non-polar substances:
02, CO2, fatty acids, steroid hormones
____ = amount of substnace crossing a surface per unit of time
flux
Diffusion between 2 compartments is always:
bi-directional
Net flux is
the difference between the two unidirectional fluxes.
What state is the system referred to as when the net flux = 0
diffusion equilibirum
2 types of mediated transport
Facilitated diffusion & Active transport
T/F
Facilitated Diffusion requires energy
FALSE
What serves as a carrier to translocate a molecule across a membrane in faciliated diffusion?
Membrane protein
Glucose is a ____ and ___ molecule
large and polar
All cells have what transporters?
glucose
Active transporters are referred to as
pumps
What can energy affect?
Affinity of the transporter for the ligand on one side of the membrane more than on the other side & rate (of transporter conformational change)
Describe the process of the primary active transport model
the energy source is the hydrolysis of atp –> transpoter becomes phosphorylated –> changes affinity for solute (ligand) –> increases transport rate.
Give me 2 examples of primary active transport:
- Transport of Na ions out of cells
2. Transport of K ions into cells
Describe the process of the secondary active transport model
uses energy in ion conc. gradient across membrane. Transporter has two binding sites.
e.g. transport of amino acids, uses [Na] gradient.
3 steps in mediated transport
- Ligand binds to transporter
- Transporter undergoes conformational change
- Ligand is released on other side of membrane
“osmalirty”
the total solute concentration in a solution. 1.0 osmol = 1.0 mole of solute. 1.0 mole of NaCl = 2.0 osmoles.
What is the osmolarity of extracellular fluid?
300 mOsm
Name the 3 types of EXTERNAL solutions?
Isotonic
hypotonic
hypertonic
Isotonic external solution?
Is there a change in cell volume?
= 300 mOsm of non-penetrating solutes –> no change in cell volume
Hypotonic external solution?
Is there a change in cell volume?
< 300 mOsm of non-penetrating solutes –> cells swell
Hypertonic external solution?
Is there a change in cell volume?
> 300 mOsm of non-penetrating solutes –> cells shrink
isoosmotic means what?
= 300 mOsm of non penetrating PLUS penetrating plus (this is the osmotic portion)
what is a normal tonicity of a cell?
300 mosmol
Lower concentration of mOsm =
higher concentration of water
ex: 200 mOsm non penetrating solutes in solution = the hypotonic solution and the cells swells.
ex: 300 mOsm non penetrating solutes = isotonic no change in volume
ex: 400 mOsm = hypoertonic –> cell shrinks because sol is higher and less water.
Define:
Endocytosis
Pinocytosis
Phagocytosis
- engulfment of fluid and particles from extra. space
- drinking small particles with or without small volume of ECF; performed by all cell types
- phagocytosis: engulfment of large particles or cellular debris; performed by specialized cells - phagocytes.
In the distribution of ions across the plasma membrane the intracellular Ca2+ is ___________. The free Ca2+ is very ____.
The organic anions aka PROTEINS are where? why?
bound or sequestered; very low (
Ohms law
V = IR V= voltage I = current R = resistance
Conductance =
membrane property. Conductance does NOT = current
Conductance is the reciprocal of resistance: G=1/R
If the R is high then the G is low. if the R is low then the G is high.
Diffusion potentials can be ______ ie. they can disappear over time. They are due to ______ ion flow which is ______________.
transient
they are due to asymmetric ion flow - an imbalance in the flow of an ion or several ions between two compartments. `
