cell Membrane/Introduction to Electrophysiology Flashcards
Eukaryotic membranes contain?
Lipid bilayer matrix: Hydrophobic!
Intrinsic and extrinsic proteins
Glycolipids and glycoproteins
What are the functions of Eukaryotic membranes
Serve as a reactive surface
serve to compartmentalize the cell
Serve to control entry and exit of molecules
Is the peripheral protein located in the Intracellular or the extracellular space?
Extracellular space and intracellular space, but on one side
what bond exist btwn the peripheral and integral protein
They are non-covalently bonded
Integral proteins are linked to phospholipids Via?
Oligosaccharides or directly to fatty acids
Factors which determine the rate of movement during passive diffusion are
area, concentrations, and distance of diffusion
What are pores
A non-gated conduit/Channel that is always open
What are channels
These are conduits that are gated by a door and open and close periodically
FYI about the gut and transport mechanism
The gut epithelial cell is an example of a cell with multiple transport mechanisms whose function is to pass nutrients from the lumen of the gut to the blood
Ion channels demonstrate selectivity based on the size of the channel opening Types T/F?
True
Types of channels
Voltage-gated •Ligand-gated •Pressure/stretch gated •Non-gated (passive leak) •Water channel (aquaporins)
What are the components of each subunit voltage-gated channel
Six transmembrane Helices
What are ion channels made up of
The ion channel structure is derived from the primary amino acid sequence. It consists of multiple subunits, each with distinct trans-membrane segments (domains) that fulfill distinct roles. also areoligomeric complexes that compose of multiple subunits
Tetramer
Voltage gated ca+,K+,Na+ channels. This is a ca+ release release channel.
Pentamer
Nicotine Ach receptor channel
Hexamer
Half gap junction channel or connexon, made up of 6 connexins.
Ionic flux and direction is determined by?
Driving force(Voltage)
what dictates the direction of ion flux, the sign of the membrane potential and the value of the membrane potential
Ion concentration gradient
What is the Nernst Equation used for
Use for determination of equilibrium potentials for any ion (Eeq)
What is the Goldman-Hodgkin-Katz equation
Use for determination of Membrane Potentials of cells(Vm) (multiple ions)
When are membrane potentials generated
During passive diffusion through channels
What determines the permeability of the cell during an influx
Cross-sectional area, diffusion coefficient, membrane Thickness
What are the things that can cotransport with Sodium into the cells
Glucose and Amino Acids Can Be Transported into Most Cells through Sodium Co-Transport. The transport carrier protein has two binding sites on its exterior side—one for sodium and one for glucose or amino acids. Again, the concentration of sodium ions is very high on the outside and very low on the inside, providing the energy for the transport. A special property of the transport protein is that the conformational change to allow sodium movement to the cell interior does not occur until a glucose or amino acid molecule also attaches.
Which substances are counter-transported out of the cells through sodium counter transport mechanism
Calcium and Hydrogen Ions Can Be Transported out of Cells through the Sodium Counter-Transport Mechanism
XX Calcium counter-transport occurs in most cell membranes, with sodium ions moving to the cell interior and calcium ions moving to the exterior, both bound to the same transport protein in a counter-transport mode.
• Hydrogen counter-transport occurs especially in the proximal tubules of the kidneys, where sodium ions move from the lumen of the tubule to the interior of the tubular cells, and hydrogen ions are counter transported into the lumen.
What is a patch-clamp
Recording technique for a single ion channel/measuring ionic flux as an electrical current.
During Electrogenic reactions in the cell whats the movement of Na and K
3 Na+ out,2 K+ in.
In a cell membrane More positive is Depolarized or Hyperpolarized
Depolarized
In a cell membrane More negATIVE is Depolarized or Hyperpolarized
Hyperpolarized
the point where the Conc gradient(chemical force) pushes out, Membrane potential(Electrical force) pushes in becomes equal to each other is called
the Nernst potential
what is the selectivity of ion channels based on?
- Size of the channel
2. Distribution of the charges that line it.
What Facilitates the opening and closing of the Voltage-gated channels?
They open and close by the changes in the membrane potential
When does the activation gates in the Na+ channels open and when do they close
Opened during depolarization, when open the nerve membrane is permeable to Na+. Its closed during repolarization.
Voltage clamp measures?
The current of the whole cell
Patch-clamp measures?
The current through a single ion channel
what is action potential
Rapid depolarization that occurs in an excitable cell, initiated by electrical event or chemical stimulation.
Depolarization makes membrane potential less negative T or F
T , cell interior becomes less negative
Does inward or outward Na+ current cause rapid depolarization during upstroke?
Inward Na+ current.
What is overshoot in an action potential graph?
the brief portion at the peak of the action potential when the membrane potential is positive
What is the mechanism of action of TTX
Tetrodotoxin (TTX) and lidocaine block voltage-sensitive Na+ channels and abolish action potentials.
What causes repolarization
repolarization is caused by an outward K+current.
What is the absolute refractory period
the period during which another action potential cannot be elicited, no matter how large the stimulus
What is the relative refractory period
An action potential can be elicited during this period only if a larger than usual inward current is provided
What is the relationship between surface area and conductance?
The surface area is directly proportional to the conductance G of a Chanel.
What is the direction in relation to the cell of the Membrane potential(Electrical force) and concentration gradient.(Chemical force)
Conc gradient(chemical force) pushes out, Membrane potential(Electrical force) pushes in.
Speed of propagation of action potential is termed?
Conduction velocity
Inactivated state of action potential detects unidirectional propagation.T/F
T; It cannot get it to go to the opposite direction
Speed of action potential depends on?
Internal diameter and Internal resistance of axon
The steps of propagation per channel are
Close,open, inactivate,close.
If diameter is large, then
internal resistance is low
and conduction velocity
is high t/F
T
what changes the capacitance of the electrical component of the Axon?
Oligodendrocytes
What’s the function of Myelin?
Myelin decreases surface areas that needs to be charged or discharged. Leaves tiny little gaps to charge and discharge..saves energy and increases conduction.
Leake or pores can be found in every cell t/f
T
In what location can we find voltage-gated chanels
Voltage-gated Na and K channels are only found in some cells, especially in excitable tissues, such as in muscle, the heart, in the retina, in the nerve cells in the nervous system, and even in egg cells.
Action potential consists of?
There are three main parts to an AP. The first involves a strong depolarization which is due to voltage-gated Na channels opening and Na flowing into the cell. A strong hyperpolarization comprises the second part and is caused by delayed rectifying K channels that are slow to open. The third part is called the undershoot and it is when the voltage is more negative than the resting membrane potential. It is due to the fact that the delayed rectifying K channels are slow to open and slow to close.
What causes inward current in a voltage clamp
inward current is caused by Na ions entering into the cell through voltage gated Na channels
what is inactivation
This time dependant conductance of the Na channels is referred to as inactivation.
Important things about potassium chanells from voltage clamp curves
Slow to activate/They Do not inactivate
Important things about the sodium chanels from voltage clamp curves is that?
Fast to activate/Inactivate quickly
whats the sodium and calcium chaneln relationship
If there is a large amount of Ca extracellularly, the Na channels perceive the cells membrane potential to be lower than it really is. For example, it thinks the membrane potential of the cell is –70 rather than the normal –60. This makes it harder to activate the Na channels because you need a greater depolarization to activate them. If the extracellular Ca concentration is low, then the Na channel perceives the cells membrane potential to be higher than it really is. Therefore, less voltage is required to open these channels and they become hyperexcitable
Factors that determine the current generated by an ion as it moves through the Chanel are?
- equillibruim potential
- membrane potential
- conductance of a Chanel
- ohms law for the cell membrane
what is present in the node of Ranvier
High-density voltage-gated sodium chanels
The following are associated with the activation of the voltage-gated k+ channel
Relative refractory period
undershoot
the action potential duration
Repolarization of the action potential
