About proteins

Proteins are very complex biomolecules presented in many type of organisms like bacteria (prokaryotic cells) and animals (eukaryotic cells). They are formed by the addition of many amino acids.

The lipid bilayer that covers the cell has many proteins encrusted in its surface. It makes the cell to be very selective in which molecules can cross the bilayer, allowing the simple diffusion for oxygen and other small molecules. Water is a big molecule to pass the bilayer so it needs to be help by a specific protein called aquaporin. The proteins presented in this bilayer function like selective transports. There is another important transmembrane protein like ATPasa that are involved in ATP production and located in the mitochondrial surface.

Proteins that go entirely across the lipid bilayer are known as integral membrane proteins and they have a big hydrophobic polypeptide region. On the other hand, we have proteins that are only located in the surface of one layer and they are called peripheral membrane proteins.

Proteins have different conformations; it means that they are able to fold themselves in order to take the most biochemical stable form. The two principal conformations are α-helixes and β-sheets. The conformation of a protein is stable in a specific physiological environment. If we change the pH (protons concentration) in order to make the medium more o less acidic, temperature or salt concentration, the protein will start denaturizing itself. And if bad conditions persist in time, the molecule could be destroyed.

Many animal proteins have carbohydrates covalently united. These carbohydrates are exposed to the surface of the cell and they function like signs to other molecules like those taking place in sperm-egg interaction, blood clotting and inflammatory responses.

We can extract and purify proteins by different methods. We could use detergents for this job like SDS (ionic) or Triton (nonionic) and then we could analyze the proteins using electrophoresis.