Gates and Channels

animal toxins

(blank) act similarly to LQT syndrome because they target Na+ inactivation gates. This leads to more Na+ enter the cells and causing a longer AP

K+ ion channels

(blank) are composed of 4 subunits with 6 transmembrane domains each (24 transmembrane domains total) forming a tetramer.

ion channels

(blank) are membrane proteins that open and close, like a "gate"

Na+ ion channels

(blank) are monomers, unlike K+ ion channels. However, they are still composed of 4 proteins with 6 transmembrane domains each - they're just linked together and thought of as one single monomer.

long QT syndrome

(blank) is a disease characterized by a prolongation of the QT interval of the electrocardiogram.

LQT syndrome type I

(blank) was discovered to be due to a mutation in the K+ channel, specifically changing the arginine to cysteine. Without the positive charge of the arginine, the K+ channel's ability to sense voltage is altered, and it doesn't open as easily, prolonging the action potential.

pain sensors

(blank) work through sensing channels (ASICs, TRPV1, or TASKs) that are connected to specific Na+ ion channels.

late

Drugs like Mexiletine, Ranolazine, and Flecainide block (blank) currents, which is why they are used to treat LQT syndrome

voltage sensing domains

How do voltage gated ion channels sense stimuli?

selectivity filter

K+ ion channels select for K+ ions through a (blank) in which molecules pointing inside the ion channel mimic the configuration that water molecules usually have around K+ ions.

inactivation

LQT syndrome is caused by a mutation in the sodium (blank) gate

increase

LQT syndrome is defined by an (blank) in the time it takes for myocytes (heart cells) to repolarize or recover from their excited state back to rest.

true

True or false: different tissues in the body have different mixtures of the same channels (i.e. they do not depolarize and repolarize the same way)

false (would not)

True or false: if TTX was added intracellularly, it would still block voltage gated sodium channels

true

True or false: ion channels are present both in the plasma membrane and in membranes of intracellular organelles

true

True or false: some drugs bind independently of the position of the activation/inactivation gates and some drugs are dependent on the position of the activation/inactivation gates

false (they have 2 gates)

True or false: voltage gated sodium channels just have one gate

charged

Voltage gated ion channels have a voltage sensing domain, which is usually made of (blank) amino acids like arginine

temperature, membrane potential, intracellular and extracellular agents (ligands)

What are 3 of the main stimulants that control gating of ion channels?

sense stimuli, open/close gate, allow ion flow

What are the three main functions of ion channels?

the Na+ channel is open longer, causing a longer AP (aka longer QT)

What is the result of a defect in the sodium inactivation gate?

patch clamping

What technique is used to measure ion flow through ion channels?

inactivation

When a membrane potential is depolarized, the (blank) gate of the voltage gated sodium channel will close to help the cell repolarize

activation

When a membrane potential reaches threshold, the (blank) gate of the voltage gated sodium channels open to help the cell depolarize

selectivity

When ion channels are open, they only allow certain substances to pass, this is called (blank)

TTX completely blocks sodium channels from the outside (we want to block late currents)

Why can we not use drugs like TTX to treat patients with LQT syndrome?