Proteins and Their Functions

Study Notes

Proteins are versatile molecules in the body with numerous functions.
The term "protein" comes from the Greek word "Proteus," meaning "primary."
Proteins are polymers of amino acids, composed of 20 different amino acids in varying numbers and sequences that are covalently linked.
The general formula for proteins is CHON.

Amino acids are large molecules (macromolecules) and the fundamental building blocks of proteins.
There are 20 different amino acids, with 8 essential amino acids that cannot be produced by the body and must be supplied through diet.
The essential amino acids are:
- Valine
- Leucine
- Isoleucine
- Phenylalanine
- Tryptophan
- Methionine
- Threonine
- Lysine

Amino acids have an electric charge that depends on the pH of the solution and the type of R group.
In basic solutions, amino acids have a negative charge, while in acid solutions, they have a positive charge.
This charge affects how proteins move in an electric field, allowing them to be separated.

The structure of a protein dictates its function.
The primary structure of a protein refers to the number and sequence of amino acids, which is determined by the DNA coding.
The primary structure determines the identity of proteins, molecular structure, binding capacity, and recognition capacity.
The secondary structure of a protein refers to the coiling and folding of the protein chain, determined by the interaction of adjacent amino acids.
The tertiary structure of a protein refers to the 3-dimensional shape governed by various covalent and non-covalent bonds.
The quarternary structure of a protein refers to the combination of two or more polypeptide chains that associate closely together.

Enzymes: biochemical catalysts that accelerate or decelerate biochemical reactions.
Structural proteins: provide structural support for the body, a tissue, or a cell, and are usually long, fibrous molecules.
Contractile proteins: involve in the contraction and relaxation of muscles, allowing movement of individuals, and are usually long, fibrous materials.
Antibodies: proteins produced by certain immune cells that effectively neutralize foreign material.