Voltage Gated Ion Channels

Active Transport

Involves the use of energy, primarily from the breakdown of ATP, to move a substrate against its gradient.

Passive transport

Involve substances moving across the cell membrane without the input of any energy.

Facilitated Diffusion

Transport process for small charged or polar solutes require assistance from plasma membrane proteins.

Channel-mediated and Carrier-mediated

What are the two types of facilitated diffusion?

electrochemical gradient

The desired movement of the ions is dependent on the?

Transport proteins

Proteins that assist in moving ions through the cell membrane.

Ion movement

A combination of the electrical and chemical concentration gradients (electrochemical gradi determines.

Inside

An ion with higher concentration outside the cell will move?

Outside

An ion with higher concentration inside the cell will move?

Electrical gradient

Neurons and other charged cells have differences in total positive and negative charges across the membrane. Inside is relatively negative and outside is relatively positive.

Na+ and K+

What are the usual positive ions in neurons?

membrane potential

The difference in charge.

Na+

Which ion is primarily found outside the neuron?

K+

Which ion is primarily found inside the neuron?

Voltage

Measure of the amount of potential difference in electrical charge as Volts (milivolts in neurons)

Current

Movement of charged particles (pumps, channels, and transporters). Greater movement, greater current (mili or picoamps in neurons).

Resting membrane potential (RMP)

Referred to as the charge across the membrane

-70 mV (under resting conditions, the inside of the cell is more negative relative to the outside).

What is the normal value of resting membrane potential.

Microelectrodes inside neuron and reference ground outside neuron

What causes the relative difference of cells?

Technique is used in conjunction with drugs to block channels allowing for isolation of specific ions, or specific channel activity. Can measure either voltage or current.

What is patch clamping?

voltage

Current clamp holds current measures?

current

Voltage clamp holds voltage and measures?

ATP

What does the sodium potassium pump (Na+ K+ pump) use to move sodium out of the cell and potassium inside?

Membrane potential

What can change allowing neuron to be excitable?

Stimulus from sensory cell → threshold of excitation is reached → repolarization occurs → membrane becomes hyperpolarized as K+ ions continue to leave cell → The K+ channel closes and restores RMP.

What are the steps of Impulse conduction?

Kir and K2p

Which two transmembrane segments portions cross the membrane

Hv

Voltage gated proton channel

TMS 4

Voltage sensor

TMS 5-6 line the pore

Act as selectivity filter