The importance of proteins
Proteins could be called the body's "multi-purpose workers". They serve living things in five main ways.
1. As a source of energy
The body uses protein for energy only as a last resort. Only when the energy from carbohydrates and fats is not enough does it break down proteins to get energy.
2. For building structural parts
Protein is one of the main materials the body is built from. An important part of the cell membrane is made of protein. The connective tissues of animals contain collagen, and hair and bird feathers contain keratin.
3. Acting as enzymes
It is enzymes that speed up every biochemical reaction that takes place inside a living thing. All of those enzymes are built from protein.
4. Acting as hormones
Many hormones are proteins. They carry messages between parts of the body, helping to coordinate them and to keep the internal conditions steady (homeostasis). Examples: insulin and growth hormone.
5. Acting as antibodies
When disease-causing microorganisms enter the body, the body produces antibodies to fight them. Those antibodies are proteins too. So the weapons of your immune system are proteins.
Remember
Put simply: carbohydrates are the body's fuel. Proteins are the building materials the body is made from, and the machines that keep it working.