1/25: Cell Membrane, Membrane Transport, and Membrane Potential V Flashcards
What is a membrane potential?
Charge difference across the plasma membrane
What is a membrane potential created by?
Unequal distribution of anions and cations across the cell membrane
What is the source of energy in a membrane potential?
Charge separation
What is the resting membrane potential?
Is the charge difference across the plasma membrane when the cell is at rest
What is normal resting Vm (membrane potential)?
-70mV (varies by cell type)
What does the sign in a Vm (membrane potential) represent?
The charge inside the cell
What does the membrane potential create?
Electrical gradients for movement of ions into/out of cells
What does the membrane potential do to ion channels?
Opens or closes gated ion channel
What does membrane potential regulate?
Exocytosis
What is an electrochemical gradient?
Two gradients for the passive transport of charged substances across the membrane
What are the two types of membrane potentials?
- Chemical gradient
- Electrical gradient
What is a chemical gradient?
Ions will move passively down concentration gradients
What is an electrical gradient?
Ions will move passively down electrical gradient
*positive ion like Na or K they will move to the negative side of the membrane because opposites attract (move to a site of unlike charge)
What does the strength of the electrical gradient depend on?
Valence of the ion and the magnitude of the membrane potential
In which direction will there be net movement of K+?
Depends which is bigger
When would there be no net movement of K+ through K+ channels?
Equal magnitude but opposite in direction
What does equilibrium potential do?
Vm that creates a ΔE that is equal in strength but opposite in direction of the ΔC (ΔE-ΔC=0)
- electrochemical equilibrium
- no net ion movement through channels via facilitated diffusion
What does the nernst equation calculate?
The equilibrium potential (E) when ion concentrations are known
If Vm= -70mV, in which direction will there be net movement of K+ via facilitated diffusion?
Net flow out of cell; down EC gradient
If Vm= -100mV, in which direction will there be net movement of K+ via facilitated diffusion?
Net flow into the cell
If Vm= -90mV, in which direction will Cl- flow via facilitated diffusion?
Out of the cell
At cell’s resting membrane potential, the equilibrium potentials for Na, K, Cl, and Ca are such that when an ion channel for one of these ions opens, the ions __________ their concentration gradient
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