The Biology of Cell Molecules: What Are Lipids and Proteins

In the field of biology, one thing that can be difficult for a lot of people understand is what lipids and proteins are. Lipids are used for long-term energy storage within the body and other helpful things. They have several unique characteristics that set them apart from the other types of molecules in cells. For example, all lipids are insoluble in water due to long nonpolar hydrocarbon chains and relative lack of hydrophilic functional groups.

One type of lipid group is fats and oils. These are used for long-term energy storage. Oils can help waterproof skin, hair, and in the case of birds, even feathers. For example triglycerides is composed of one glycerol and three fatty acids. There are two of fatty acids: saturated and unsaturated. A saturated fatty acid has no double bonds between carbon atoms. This is why, for example, butter is solid at room temperature. Unsaturated fatty acids, on the other hand, have one or more double bonds between their Carbon atoms. This is what makes oils liquid at room temperature.

Phospholipids are yet another type of lipid group. What these do is form the bulk of plasma membrane. One end, the polar phosphate head, is water soluble. However the other end, the nonpolar fatty acid tail, is not water soluble.

Another type of lipid group are steroids. A steroid is essentially a lipid that is made of four fused rings. They do not have fatty acids but they are insoluble in water. The way they are made is that they are derived from cholesterol. The only difference amongst steroids is that they differ in functional groups only.

Proteins have many functions, such as supporting metabolism defense, regulation, and transportation. They are composed of amino acid monomers. The central carbon is bonded to a hydrogen atom, amino group, carboxyl group, and a side chain. There are 20 different amino acids that are formed by these bonds.

A peptide bond is formed by the dehydration reaction between two amino acids. A peptide is two or more amino acids that have been covalently linked. Furthermore, a polypeptide is a chain of many amino acids that have joined my peptide bonds. The sequence determines the final shape of the protein.

Proteins differ in shape because they all have different functions. The primary structure is determined by the amino acid sequence. The secondary structure are portions of chain that have formed helices or pleated sheets. Tertiary structure is the overall 3-D shape of the secondary structures.