Why can Valinomycin cross the membrane?

Because valinomycin is uncharged and contains no ionizable groups, it acquires the charge of the complexed ion. Both the uncomplexed and complexed forms of valinomycin are able to diffuse across the membrane.

How do ions cross the lipid bilayer of the cell membrane?

Although ions and most polar molecules cannot diffuse across a lipid bilayer, many such molecules (such as glucose) are able to cross cell membranes. Once open, channel proteins form small pores through which ions of the appropriate size and charge can cross the membrane by free diffusion.

How does Valinomycin transport K ions?

Valinomycin is a naturally occurring dodecadepsipeptide used in the transport of potassium and as an antibiotic. It functions as a potassium-specific transporter and facilitates the movement of potassium ions through lipid membranes “down” the electrochemical potential gradient.

How does Valinomycin select potassium ions over other ions?

K-channels and valinomycin molecules share the exquisite ability to select K+ over Na+ ions. In such a phase-activated state, electrostatic interactions from these 8-fold binding sites, constrained to maintain high coordinations, result in K+/Na+ selectivity with no need for a specific cavity size.

What is Valinomycin used for?

Valinomycin is a potent antibiotic. It is commonly used as an agent to induce apoptosis and can also be used to calibrate potentiometric responses in membrane experiments involving potential-sensitive dyes such as di-4-ANEPPS.

How does Valinomycin affect cellular respiration?

Valinomycin produces higher steady state potassium phosphate swelling which can be reversed to give active shrinkage if mersalyl is added to block the Pi−/OH− antiporter. Respiration declines concurrently. Uncouplers accelerate the shrinkage and restore the respiration.

How are ions transported across the cell membrane?

The mechanisms that transport ions across membranes are facilitated diffusion and active transport. Facilitated diffusion of solutes occurs through protein-based channels. Active transport requires energy in the form of ATP conversion, carrier proteins, or pumps in order to move ions against the concentration gradient.

How are ions transported across the cell?

To move substances against a concentration or electrochemical gradient, the cell must utilize energy in the form of ATP during active transport. Primary active transport, which is directly dependent on ATP, moves ions across a membrane and creates a difference in charge across that membrane.

What is the structure of Valinomycin?

Valinomycin is a twelve-membered cyclodepsipeptide composed of three repeating D-alpha-hydroxyisovaleryl-D-valyl-L-lactoyl-L-valyl units joined in sequence. An antibiotic found in several Streptomyces strains.

What is the structure of valinomycin?

What type of inhibitor is valinomycin?

Combination of concanamycin A, a vacuolar proton-ATPase inhibitor, and valinomycin, an ionophore that promotes K(+) efflux from cells, powerfully prevented poliovirus infection.

How does Valinomycin inhibit ATP synthesis?

Valinomycin slows mitochondrial ATP synthesis without blocking electron transfer to O2 (Table 18-4). (b) Valinomycin combines reversibly with K+ ions to form a membrane-permeable complex that diffuses across the inner membrane and releases K+ on the inside.

Why do lipid molecules move about in the bilayer of the membrane?

Because the lipid bilayer is somewhat thicker in the rafts, certain membrane proteins (more…) For the most part, lipidmolecules in one monolayer of the bilayer move about independently of those in the other monolayer.

What happens when the bilayer of a cell membrane is torn?

A small tear in the bilayer creates a free edge with water; because this is energetically unfavorable, the lipids spontaneously rearrange to eliminate the free edge. (In eucaryotic plasma membranes, larger tears are repaired by the fusion of intracellular vesicles.)

What happens when a charged molecule tries to pass through the bilayer?

Charged molecules have polarity, just like the water. Lipid bilayer membrane is made of polar phosphate head and nonpolar lipid part. Even though the head is hydrophilic the tail part is hydrophobic, which means it repels the water. So, when a polar/charged molecule tries to pass through…

How does cholesterol enhance the permeability-barrier properties of the lipid bilayer?

The cholesterol molecules enhance the permeability-barrier properties of the lipid bilayer. They orient themselves in the bilayer with their hydroxylgroups close to the polarhead groups of the phospholipid molecules.