The special structures in the cell membrane that allow materials like water and sugar to pass through are called transport proteins. These proteins are made of amino acids, which are the building blocks of all proteins.

Here's a breakdown:

* Amino acids: These are small organic molecules that link together to form long chains called polypeptides.

* Polypeptides: These chains fold into complex three-dimensional structures to form functional proteins.

* Transport proteins: These proteins are specifically designed to bind to and move certain molecules across the cell membrane.

There are two main types of transport proteins:

* Channel proteins: These proteins form pores or channels through the membrane, allowing specific molecules to pass through passively, driven by a concentration gradient.

* Carrier proteins: These proteins bind to specific molecules and change shape to transport them across the membrane, sometimes requiring energy.

So, the structures in the cell membrane allowing passage of water and sugar are made of amino acids that form transport proteins with specific functions.