What are the 20 Types of Proteins?
There's a slight misunderstanding in the original question. Proteins aren't categorized into 20 types in the way that, say, different species of animals are categorized. Instead, proteins are built from 20 different amino acids. These amino acids are the building blocks, and the specific sequence and arrangement of these amino acids determine the type of protein. The diversity of proteins arises from the almost infinite number of possible combinations of these 20 amino acids.
The 20 amino acids that serve as the building blocks for all proteins are:
- Alanine
- Arginine
- Asparagine
- Aspartic acid
- Cysteine
- Glutamic acid
- Glutamine
- Glycine
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Proline
- Serine
- Threonine
- Tryptophan
- Tyrosine
- Valine
Several sources confirm this list, including Britannica, StatPearls, and Ajinomoto.
Types of Proteins Based on Function
While there aren't 20 types of proteins based on their inherent nature, proteins are categorized based on their function. Examples include:
- Enzymes: Catalyze biochemical reactions (e.g., lactase, which breaks down lactose).
- Antibodies: Part of the immune system, fighting off infection (e.g., immunoglobulins).
- Structural proteins: Provide support (e.g., collagen in connective tissue).
- Hormones: Chemical messengers (e.g., insulin, regulating blood sugar).
- Transport proteins: Carry molecules across cell membranes (e.g., hemoglobin carrying oxygen).
- Contractile proteins: Enable muscle movement (e.g., actin and myosin).
Physiopedia mentions seven types of proteins, but this is just a subset of the many functional classes. The number of protein types is vast and constantly being expanded as new proteins are discovered.
Essential vs. Non-Essential Amino Acids
It's important to note that while our bodies can produce eleven of these amino acids (non-essential), the remaining nine (essential amino acids) must be obtained through diet. This distinction is vital for maintaining proper nutrition.
