Cell Physiology 1: Membrane Potentials Flashcards
electrical signalling is the ability of ____ and ___ cell types to ___ and ___ electrical signals
muscle and nerve; generate and carry
electrical signalling is dependent on distribution of ___ across a cell membrane
ions
total body water is approximately what % of a human’s body weight?
50-70%
what amount of of total body water is intracellular fluid?
2/3 (two thirds)
what amount of total body water is extracellular fluid?
1/3
what percent of extracellular fluid is interstitial fluid?
80%
what percentage of extracellular fluid is plasma?
20%
the concentration of K+ ions is higher ___ (inside or outside) the cell
inside
the concentration of Na+ ions is higher __ (inside or outside) the cell
outside
the concentration of Cl- is higher __ (inside/outside) the cell
outside
the concentration of non-Cl- anions is higher ___ (inside/outside) the cell
inside
the concentration of Ca2+ ions is higher __ (inside/outside) the cell
outside
how are the ion concentrations across a cell membrane maintained?
the lipid bi-layer doesn’t allow free passage of ions
the lipid bi-layer is permeable to ____ but not __
fat soluble things; water soluble things
the core of the lipid-bilayer is very __ (hydrophilic or hydrophobic)
hydrophobic
where do the concentration gradients across cell membranes come form in the first place?
proteins that move ions across by active transport
what is the name of the protein that pumps Na+ and K+ across the cell membrane
sodium/potassium ATPase
the sodium potassium pump actively transports __ (#) Na+ __ (in/out) and __(#) K+ ___ (in/out)
3 Na out; 2K in
the sodium potassium pump moves Na/K ___ (down/against) their concentration gradient
against
what energy source is used for the sodium potassium pump to actively transport ions?
ATP hydrolysis
Describe the steps of the transport done by the sodium potassium pump
- Protein opens to the inside and 3 sodium bind
- protein is phosphorylated by ATP (ATP becomes ADP)
- phosphorylation caused protein to open to the outside and release Na+
- the open protein can then bind 2 K
- dephospho rylation of the protein causes it to open to the inside and release the K+
T/F the sodium potassium pump is constantly working in the background, even when nothing else is happening in the cell
true
what is the benefit of the protein needing to be either phosphorylated/dephosphorylated to change direction of opening?
prevents protein from being open to both sides, allowing regulation of which ad how many ions come in/out
what type of proteins are largely involved in creating electrical gradients?
ion channels
T/F ion channel proteins can be continuously open
true
T/F ion channel proteins only allow 1 specific type of ion to pass
true
t/f ion channel proteins have gates that can close
true
channel-mediated movement is both __ and __
very fast and passive!
channel proteins allow for __ diffusion down a ___ gradient
passive;
electrochemical
b/c ion channels are gated and selective they can change their __ to different ions independently
permeability
the extracellular fluid has a very slight __ charge
positive
the intracellular fluid have a very slight __ charge
negative
the very small imbalance of charge across a cell membrane creates a __
resting potential
charge imbalance across a membrane causes a ___ force, promoting the __ of ions across a membrane
electro-motive; movement
T/F charge distribution affects the movement if ions across a membrane
true
the charge imbalance across a membrane that creates an electro-motive force results in a membrane __
potential
the membrane potential affects the distribution of ions by __
electrostatic attraction and repulsion
explain how an electrochemical gradient is made across the cell membrane
the movement of ions down their concentration gradients will eventually create an electrical gradient that will cause an ion to move against its concentration gradient until equilibrium is reached
what is the equilibrium potential of sodium?
+60 mV
what is the equilibrium potential of potassium?
-90mV
the equilibrium potential of sodium being +60mV means __
that the inside of the cell will be +60mV more positive than the outside
the equilibrium potential of potassium being -90mV means__
that the inside of the cells will be -90mV more negative that the outside of the cell
what equation is used to calculate equilibrium potential?
Nernst
what is an equilibrium potential?
the electrical gradient (voltage) needed to balance the concentration gradient
t/f leak ion channels are constantly working as background function in cells
true
if you want to calculate resting potential of a cell considering all ions that are capable of crossing the membrane, what equation would you use?
the GHK
what is th resting potential of muscle and nerve cells?
-70mV
why is the resting potential closer to the equilibrium potential of potassium than sodium?
the resting permeability of potassium is much (25x) greater than that of sodium
at the resting potential, the K electrochemical gradient is __ (inward/outward)
outward
how can we change the resting potential value?
by changing the permeability of ions
what would happen to the resting potential if we increased the permeability of K? what is this process called?
K will leave cell, causing it to become more negative, thus moving more towards the equilibrium potential of K. Hyperpolarization
what would happen to the resting potential if we increased the permeability to Na? what is this process called?
Na will enter cell, becoming more +, this moving towards ENa. Depolarization
when changing the permeability, what equation can be used to predict the new membrane potential?
GHK
