Question

why do phospholipids form a bilayer in water?
the phosphate portions repel each other
the hydrophilic and hydrophobic parts attract each other
the phosphate portions attract water, and the lipid portions repel water
the lipid portions attract water, and the phosphate portions repel water

Explanation:

Phospholipids have a phosphate - containing hydrophilic (water - attracting) head and lipid - based hydrophobic (water - repelling) tails. In water, the hydrophilic heads interact with water, while the hydrophobic tails cluster together away from water. This arrangement forms a bilayer.

• The first option is incorrect because phosphate portions are hydrophilic and interact with water, not repel each other.
• The second option is wrong as hydrophilic and hydrophobic parts do not attract each other; they have different interactions with water.
• The fourth option is incorrect since lipid portions are hydrophobic (repel water) and phosphate portions are hydrophilic (attract water).

Answer:

The phosphate portions attract water, and the lipid portions repel water.