What Is a Protein?

A protein is a large, complex molecule that is a key building block of life. We all know that it is an important part of our diets, but how many of us know how protein actually works in our bodies, and why we need it?

What It Is

Protein is vital to the functioning of cells in living organisms. Proteins are required for the structure and regulation of the body’s tissues and organs. They are made up of long chains of amino acids—at least 20 different types of amino acids, in fact.

Nine of the amino acids that people need to for making protein—histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine—must come from food.

How It Works

There are as many as 100,000 unique types of proteins within a typical human cell. The functioning of each depends on its shape.

A protein begins in the cell as a long chain of about 300 building blocks (on average) known as amino acids. There are more than 20 different types of amino acids, and how they are ordered determines how the protein chain will fold upon itself and take shape.

Once a protein has its shape, it can bind to other selected molecules in order to carry out its function. That function could be signaling, storing, transporting, providing structure, fighting foreign invaders, acting as a catalyst, or another function.

Types of Protein and Their Uses

Proteins come in a variety of types, according to function. These include the following:

Antibody

These are components of the immune system that help to protect the body from foreign particles, such as viruses and bacteria. Proteins recognize and bind themselves to foreign substances in order to neutralize them and help protect the body. An example is of an antibody is immunoglobulin G (IgG).

Enzyme

Enzymes carry out almost all of the chemical reactions happen in cells, and also help new molecules to form by reading the genetic information stored in DNA. An enzyme increases the speed at which a chemical reaction happens.

An example of an enzyme is phenylalanine hydroxylase. This enzyme catalyzes the breakdown of the amino acid phenylalanine. Infants born unable to make this enzyme have toxic effects from the incomplete metabolism of phenylalanine.

Messenger

Also known as signaling proteins, they allow communication between cells. They include some types of hormones. These proteins transmit signals to coordinate biological processes between cells, tissues, and organs. An example of a messenger protein is somatotropin, also known as growth hormone.

Structural

Structural proteins allow cells to maintain their shape and organization. On a larger level, they provide the structural elements of connective tissues such as bone and cartilage and help muscles to function. An example of a structural protein is actin.

Transport and Storage

Transport and storage proteins attach themselves to atoms and small molecules, storing or carrying them within cells and throughout the body. An example is ferritin, which stores iron for use by blood cells and other body tissues.

How Much You Need

You likely won’t have problems getting enough protein. According to an analysis published in Public Health Nutrition, people in the U.S. consume more protein than is needed each day.

The study found that men ages 20 and above take in 234 grams (8.3 ounces) of protein per day (from sources including meat, dairy, fish, seafood, eggs, nuts, legumes, and soy), 72% coming from meat; while women take in 148 grams (5.2 ounces) of protein daily, with 70% from meat.

The daily nutritional goals set by the U.S. Department of Agriculture (USDA) are about 6.5 ounces of protein for men ages 19 and over and about 5 ounces for women. There is no single optimal recommended ounce amount of protein because many factors contribute to an individual's ideal protein consumption (age, exercise, hormones, medical conditions, and overall calorie requirements, to name a few).  

How to Get Enough in Your Diet

Since protein is integral to the function of every cell in your body, it’s important to get enough of the macronutrient in your diet—from healthy sources. Getting your protein from diverse sources, including ones that are plant-based, will give you the healthiest balance.

The protein food group includes meat, poultry, seafood, legumes (beans, peas, and soy products), eggs, nuts, and seeds. The USDA recommends opting for leaner, less fatty meat and poultry items, as well as consuming at least 8 ounces of cooked seafood per week if you are not a vegetarian.

Protein Deficiency

Protein deficiencies are rare for people in wealthier countries, such as the United States. Even vegetarians and vegans typically take in more than the daily recommended amount of protein, according to a review of scientific literature published in the journal Nutrients.

However, a form of malnutrition called kwashiorkor can develop in places experiencing famine, natural disasters, or other disruptions to the food supply. Caused by not having enough protein in the diet, kwashiorkor’s symptoms include:

• An enlarged, protruding belly
• Decreased muscle mass
• Diarrhea
• Failure to gain weight and grow in children
• Fatigue
• Fading skin color
• Changes to hair color or texture
• Increased and more severe infections
• Irritability
• Swelling ankles and feet

With early nutritional treatment, children with kwashiorkor can recover fully. However, permanent physical and mental impairments can take place if treatment is. If treatment comes too late, shock, coma, and death can result.

A Word From Verywell

As protein is contained in every cell of the body, it’s important to know how it works and how to get enough of it in your diet. However, it’s best to focus more on focus on taking in healthy sources of protein rather than consuming a lot of it.