What are the two types of proteins?

The two primary types of proteins are indeed best classified as globular and fibrous proteins. Globular proteins are characterized by their compact, spherical shapes and are typically soluble in water. They play critical roles in bodily functions, including enzymes, hormones, and antibodies. Examples include hemoglobin and enzymes. On the other hand, fibrous proteins are long, thread-like structures that are generally insoluble in water and provide structural support, such as collagen in connective tissues and keratin in hair and nails.

Essential and non-essential amino acids refer to the building blocks of proteins rather than types of proteins themselves; essential amino acids cannot be made by the body and must be obtained from the diet, while non-essential amino acids can be synthesized by the body. The distinction between animal and plant proteins speaks to sources of protein rather than their structural classification. Lastly, saturated and unsaturated proteins are terms used in lipid science to describe types of fats, not proteins. Therefore, the correct classification of proteins is by their shape and function as globular and fibrous.