Phospholipids have both hydrophobic and hydrophilic ends. How does this structure make the phospholipid ideally suited to the selectively permeable structure needed by the plasma membrane?

The hydrophobic core of plasma membrane made of hydrophobic tails of phospholipids allows only small, uncharged and non polar substances to cross the membrane.

Explanation:

Phospholipids are amphipathic molecules with hydrophobic tails and hydrophilic heads. The plasma membrane is made of a bilayer of phospholipids in which proteins are embedded. The hydrophobic tails of the phospholipids are buried in the core of the bilayer away from the water while their hydrophilic heads are oriented towards the surrounding watery medium.

This arrangement of phospholipids makes a hydrophobic core of bilayer through which only small, hydrophobic and uncharged molecules can be transported. This is the reason that plasma membrane is selectively permeable and allows only certain substances to pass through it.

Phospholipids have phosphate group heads that are hydrophilic while the fatty acid tails are hydrophobic.

They are able to form cell membrane as they automatically arrange themselves in the required pattern in water because of these properties. To form membranes, these line up next to each other with their heads on the outside of the cell and their tails on the inside. A second layer of phospholipids also forms with heads on the inside of the cell and tails facing away.

In this way a double layer is formed with phosphate group heads on the outside, and fatty acid tails on the inside. This double layer, called a lipid bi-layer, forms the main part of the cell membrane.