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.Not ATP-dependent, Activation may result in increased membrane lipid symmetry, ABC transporter, translocate lipids from outer (extracellular) leaflet to inner (cytosolic) leaflet, translocate phosphatidylserine, preventing apoptosis and engulfment by macrophages, move phospholipids from inner (cytoplasmic) leaflet to outer (extracellular) leaflet, move phospolipids across the lipid bilayer down the concentration gradient

Answer 1

Answer:

• flippases translocate lipids from outer (extracellular) leaflet to inner (cytosolic) leaflet,

• floppases, move phospholipids from inner (cytoplasmic) leaflet to outer (extracellular) leaflet, ABC transporter, move phospolipids across the lipid bilayer down the concentration gradient

• scramblases Not ATP-dependent, Activation may result in increased membrane lipid symmetry, translocate phosphatidylserine,  preventing apoptosis and engulfment by macrophages,  

Explanation:

Flipases are transportes that require energy for their functioning (ATP dependent) beause they move phospolipids across the lipid bilayer against the concentration gradient  (from extracellular side to cytosolic side).

Floppases are ABC transporters, opposite than flippases (move phospholipids from the cytosolic side).

Scrablases are bidirectional transporters, responsible for asymmetry formation. It also enables exposure of phosphatidylserineon the outer leaflet when it is necessary.