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. classify each phrase as describing flippases, floppases, or scramblases.

Flippase, floppase and scramblases are transport protein that helps in the movement of lipid molecules between the two leaflets of the Phospholipid bilayer of the plasma membrane.

Explanation:

Flippases

They are the trans membrane protein that helps in the transport of lipid molecules from the extracellular region to the cytoplasmic region.Flippases belong to ATP binding cassette (ABC) transporter protein family.

Floppases

They also act as lipid transporter which helps in the movement of lipid from cytoplasmic region to the extracellular region of the phospholipid bilayer.

Scramblases

These proteins help in the movement of lipid molecules between the two leaflet of the lipid bilayer of the plasma membrane.Scramblase with its catalytic activity helps in the transport of negative charged phospholipid such as phosphotidly ethanolamine from the inner leaflet to the outer leafet and viceversa.