Question

this is an image of the phospholipid bilayer. what are the structures forming the sheets on the outside called (labeled 3)?
a) sodium - potassium pump
b) helper protein
c) hydrophobic tail
d) hydrophilic head
(image by openstax (cc by 3.0)
via wikimedia commons.)

Explanation:

In a phospholipid bilayer, phospholipids have a hydrophilic (water - attracting) head and a hydrophobic (water - repelling) tail. The hydrophilic heads are oriented towards the outside (aqueous environment) and inside of the cell, while the hydrophobic tails are in the middle. The structures on the outside (labeled 3) are the hydrophilic heads. Option A (sodium - potassium pump) and B (helper protein) are proteins involved in transport or other functions, not the main structural components of the bilayer's outer sheets. Option C (hydrophobic tail) is in the interior of the bilayer, not on the outside.

Answer:

D) Hydrophilic head