04 Resting Potential Flashcards
2 What is the formula for salt?
NaCl
2 Water molecules are nonpolar.
False
2 What is an anion and cation?
Negatively and positively charged molecules respectively
3 How thick is the lipid bilayer?
5 nm
4 How is separation of charges responsible for potential?
Charges line up along the membrane and the rest of the fluid is electrically neutral. You only get the membrane potential right up against the membrane because the + and - charges line up on the membrane.
4 What are the two basic properties that account for resting membrane potential?
1)Unequal distribution of key ions across the cell membrane. (like more sodium than potassium ions) 2) Differences in membrane permeability to these ions.
5 How long does it take for charge to become evenly distributed after depolarization?
100 picoseconds or 10-10 seconds
6 Hyperpolarization and what cause it?
Increase in potential (polarization). Membrane more negative than resting membrane potential. Reason: The extra K+ that go out of the channel because the gate is slow to close.
8 How do Ions get across the membrane:
through pumps, channels and exchangers
8 What is a gated channel?
A channel that is only open when it is bound by a specific molecule or ion.
8 What are exchangers in a cell membrane?
A channel that will trade an ion from the cytosol with an ion outside the cell.
8 Which pore is designed to maintain polarity across the cell membrane?
Na/K pump.
8 Why is it that potassium ions are more free to move in and out of the cell, while sodium ions are not?
Potassium ions are free to move across many channels, while sodium relies on gated channels.
8 How long does it take for ions to find gate and move through it?
Milliseconds
11 How does diffusion work?
Molecules move from an area of high concentration to low concentration
12 What does Ohm’s Law describe?
Describes ionic current flow across the membrane for a particular ion.
14 What keeps the cell polarized?
Transmembrane potential
15 What do you find mostly in the cytosol?
Potassium
15 Considering that the cytosol has a lot of potassium ions (positively charged), how is it that the cytosol carries a negative charge?
Cytosol also contains many negatively charged proteins, phosphates, and chlorine anions.
16 The equilibrium state for charged molecule (ions) is determined by what?
electrochemical gradient
16 What is the Electrochemical equilibrium potential (Eion) ?
When electrical and concentration gradients exactly balance one another. Resulting in no net movement of a specific ion across the membrane.
17-18 What are the concentration gradients for K+ and Na+? And what is the electrical gradient for K+ and Na+?
Concentation gradient for K+ is outward, for Na+ is inward. Electrical gradient: inward for both.
17 It takes a large change in ion concentration to trigger depolarization.
False: a change of 10-5 mM of K is sufficient to change membrane potential from 0mV to - 80mV
18 How thick is the cell membrane?
Membrane is less than 5nm thick
22 Potassium is _____X more permeable than sodium.
40
19 Each ion has its own equilibrium potential.
True
21 How do you measure resting membrane potential?
Nernst equation
21 What is the resting membrane potential of potassium ions?
-80mV
21 What is the resting membrane potential of sodium ions?
61.54 mV
22 Which way is chlorine going to move if the resting potential outside the cell is 65 mv and inside the cell is 65 mv?
Not moving anywhere because chlorine is the same value as the resting membrane potential
23 What does the Goldman equation calculate?
Calculates the resting membrane potential based on the relative permeability of different ions
23 What is the ratio of sodium outside the cell to inside the cell?
10: 1
23 According to Goldman’s equation, what is the average resting membrane potential of a cell?
-65mV
24 Concentration gradients are created and maintained by ______?
Active transporters: ATPase pumps; Ion exchangers; Co- transporters etc.
26 What does the blood brain barrier limit?
Potassium
26 ____________ have potassium pumps and channels that move K+ into the cell.
Astrocytes
