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What are proteins and what do they do?
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Howgeneswork

What are proteins and what do they do?

Proteins are large, complex molecules composed of amino acid chains that perform the vast majority of work within cells to maintain the body's tissues and organs.

Structure and Function

Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached in long chains. There are 20 different types of amino acids. The specific sequence of these amino acids determines each protein’s unique 3-dimensional structure and its specific function. These amino acids are coded by combinations of three DNA building blocks (nucleotides) determined by the sequence of genes.

Examples of Protein Functions

Proteins perform a wide range of critical roles in the body:

  • Antibody: These bind to specific foreign particles, such as viruses and bacteria, to help protect the body.
  • Enzyme: These carry out almost all of the thousands of chemical reactions that take place in cells and assist with the formation of new molecules by reading genetic information stored in DNA.
  • Messenger: These proteins, such as some types of hormones, transmit signals to coordinate biological processes between different cells, tissues, and organs.
  • Structural component: These proteins provide structure and support for cells and allow the body to move.
  • Transport/storage: These proteins bind and carry atoms and small molecules within cells and throughout the body.

Frequently Asked Questions

The general recommendation is about 0.8 grams of protein per kilogram of body weight for most adults. If you’re older than 65, you might need 1.0–1.2 grams/kg to help preserve muscle mass. Athletes, people doing heavy resistance training, or those recovering from injury may benefit from 1.2–1.6 grams/kg. Adjusting intake based on weight, activity level, and health goals is key.
Yes, plant‑based diets can meet protein needs. Focus on high‑protein foods such as lentils, chickpeas, black beans, quinoa, tofu, tempeh, edamame, seitan, and nuts. Pair different plant proteins (e.g., rice with beans) to ensure you get all essential amino acids. A well‑planned vegan diet can provide 1.0–1.2 grams/kg of protein.
In healthy individuals with normal kidney function, high protein intake (up to 2.0–2.5 grams/kg) is generally safe and does not cause kidney damage. However, people with pre‑existing kidney disease should limit protein to prevent further stress on the kidneys. Always discuss your protein goals with a healthcare provider if you have kidney concerns.===
Common signs include muscle weakness, fatigue, hair thinning, slow wound healing, and frequent infections. In severe cases, you may notice swelling (edema) or a loss of appetite. If you notice these symptoms, check your dietary intake and consider a blood test for albumin or pre‑albumin levels.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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