protein

American  

[proh-teen, -tee-in] / ˈproʊ tin, -ti ɪn /

Also proteid

noun

• proteins
  plural

1. Biochemistry. any of numerous, highly varied organic molecules constituting a large portion of the mass of every life form and necessary in the diet of all animals and other nonphotosynthesizing organisms, composed of 20 or more amino acids linked in a genetically controlled linear sequence into one or more long polypeptide chains, the final shape and other properties of each protein being determined by the side chains of the amino acids and their chemical attachments: proteins include such specialized forms as collagen for supportive tissue, hemoglobin for transport, antibodies for immune defense, and enzymes for metabolism.

2. the plant or animal tissue rich in such molecules, considered as a food source supplying essential amino acids to the body.

3. (formerly) a substance thought to be the essential nitrogenous component of all organic bodies.

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adjective

1. Biochemistry. of the nature of or containing protein.

protein British  

/ ˈprəʊtiːn /

noun

1. any of a large group of nitrogenous compounds of high molecular weight that are essential constituents of all living organisms. They consist of one or more chains of amino acids linked by peptide bonds and are folded into a specific three-dimensional shape maintained by further chemical bonding

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protein Scientific  

/ prō′tēn′ /

1. Any of a large class of complex organic chemical compounds that are essential for life. Proteins play a central role in biological processes and form the basis of living tissues. They consist of long chains of amino acids connected by peptide bonds and have distinct and varied three-dimensional structures, usually containing alpha helices and beta sheets as well as looping and folded chains. Enzymes, antibodies, and hemoglobin are examples of proteins.

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Closer Look

Proteins are the true workhorses of the body, carrying out most of the chemical processes and making up the majority of cellular structures. Proteins are made up of long chains of amino acids, but they don't resemble linear pieces of spaghetti. The atoms in these long chains have their own attractive and repulsive properties. Some of the amino acids can form bonds with other molecules in the chain, kinking and twisting and folding into complicated, three-dimensional shapes, such as helixes or densely furrowed globular structures. These folded shapes are immensely important because they define the protein's function in the cell. Some protein shapes fit perfectly in cell receptors, turning chemical processes on and off, like a key in a lock, whereas others work to transport molecules throughout the body (hemoglobin's shape is ideal for carrying oxygen). When proteins fail to take on their preordained shapes, there can be serious consequences: misfolded proteins have been implicated in diseases such as Alzheimer's, mad cow, and Parkinson's, among others. Exactly how proteins are able to fold into their required shapes is poorly understood and remains a fundamental question in biochemistry.

Other Word Forms

Derived Forms

• nonprotein
  noun
• proteinaceous
  adjective
• proteinic
  adjective
• proteinous
  adjective

Inflected Forms

Nouns

• proteins
  plural

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Etymology

Origin of protein

First recorded in 1835–45; from German Protein, from Greek prōte(îos) “primary” + German -in -in ²; replacing proteine, from French; cf. proto- ( def. )

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Explanation

Protein makes up your nails, your hair, and the egg on your plate. This nitrogenous substance we call protein consists of chains of amino acids and is necessary for life functions. The linguistic origins of protein — from the Greek proteios, meaning “first place” or “primary” — are fitting for a substance that is one of life’s chief components. Although protein is a word often heard in labs and biology classes, it has everyday context too, particularly in the kitchen. Protein-rich foods like eggs, cheese, meats, peanuts or beans are an essential part of good nutrition.

Example Sentences

See Examples For:

protein proteins

When they restored the cellular cleanup process or removed synuclein protein in their experiments, the neurons were protected from damage.

From Science Daily ● Nov. 1, 2026

However, the protein can accumulate in abnormal clumps that are closely associated with Parkinson's disease.

From Science Daily ● Nov. 1, 2026

It produces claudin-4, a protein that helps neighboring cells form tight junctions, the seals that limit the movement of substances between cells and help maintain the intestinal barrier.

From Science Daily ● Oct. 31, 2026

This was a soluble protein carrying sequences from claudin-4, designed to attract BFT without allowing it to attack the colon's protective lining.

From Science Daily ● Oct. 31, 2026

“Not with your fingers, Pigeon. And have you had any protein today?”

From "Liar & Spy" by Rebecca Stead

Their experiments pointed to a disruption in autophagy, a natural cellular maintenance process that helps remove damaged proteins and other unwanted material.

From Science Daily ● Nov. 1, 2026

Small molecules are compounds that can sometimes be developed into medicines, while biologics are treatments made from or involving biological materials, such as proteins.

From Science Daily ● Oct. 31, 2026

BFT belongs to a class of enzymes called proteases, which cut other proteins.

From Science Daily ● Oct. 31, 2026

The poster child of scientific AI is the UK-based firm Google DeepMind, which in 2020 solved one of biology's biggest problems: how proteins in living things fold into their precise shapes.

From BBC ● Oct. 28, 2026

Matter changes hands, atoms flow in and out, molecules pivot, proteins stitch together, mitochondria send out their oxidative dictates; we begin as a microscopic electrical swarm.

From "All the Light We Cannot See" by Anthony Doerr

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