Question

Lipids in a bilayer can diffuse laterally at a relatively fast rate, but \"flip-flop\" from one leaflet to the other very slowly without catalysis. three protein families –flippases (or flipases), floppases, and scramblases – catalyze the movement of lipids across the bilayer. sort each of the phrases as describing flippases, floppases, or scramblases. choose the best, most-specific enzyme name. note: if you answer any part of this question incorrectly, a single red x will appear indicating that one or more phrases are sorted incorrectly.

Answer 1

1)Flippases are proteins able translocate lipids from the outer leaflet( extracellular) to inner leaflet (cytosolic); They are enzymes that depend on ATP to function.
Phospholipid flippases,translocate phospholipids against a concentration gradient.
2)Floppases- move lipids from the inner leaflet (cytosolic) to inner leaflet ( extracellular). Floppases are ABC-transporters that do the opossite of the flippases.

3)scramblases- The activity of scramblases does not require energy (not ATP dependent). Their activation can result in increased symmetry between phospholipids of both leaflets of the lipid bilayer.
Scramblases translocate phosphatidylserine, preventing apoptosis and engulfment by macrophages.