Protein

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A 3D diagram of the protein myoglobin showing turquoise alpha helices. This protein was the first to have its structure solved by X-ray crystallography. Towards the right-center among the coils, a heme group (shown in grey) with a bound oxygen molecule (red)

Introduction[edit | edit source]

Proteins are intricate, long-chain molecules constructed from smaller components known as amino acids. Bound by peptide bonds, these biomolecules serve as the essential building blocks for almost every biological process in living organisms.

Composition and Structure[edit | edit source]

These biochemical compounds are made up of one or more polypeptides that take on either a globular or fibrous configuration.[1]

A single polypeptide is a linear polymer chain of amino acids, the order of which is determined by the DNA sequence of a specific gene.[2] The genetic code enumerates 20 standard amino acids. However, post-synthesis, several of these amino acids undergo chemical modifications, influencing the protein's folding, stability, activity, and overall function. Some proteins might also possess non-peptide groups, known as cofactors, which play a crucial role in their functions.

Functions and Importance[edit | edit source]

Proteins hold paramount importance in the life processes of all cells. Comparable to other biological macromolecules, such as polysaccharides and nucleic acids, proteins are involved in almost every cellular process:

Acting as enzymes, many proteins catalyze biochemical reactions essential to metabolism. Some proteins provide structural or mechanical roles, as evident in muscles and within cellular structures like the cytoskeleton, which maintains cell shape. Many others play crucial roles in cell signaling, immune responses, and the process of cell division.

Dietary Importance for Humans[edit | edit source]

Egg whites, a rich source of protein

Depending on their shape and structure, proteins assume varying functions. They can be predominantly found in meat, muscle, and are integral for growth, repair, and bone strengthening. Essential for the formation of tissue and cells, proteins are present in animals, plants, fungi, bacteria, and also in the human body.

Rich protein sources like milk, eggs, meat, fish, beans, spinach, and nuts are staples in many diets. The primary factors determining protein functions are:

Amino acid order, with 20 distinct amino acid types. Minor chain twists. Overall protein structure. The presence of different sub-units, like in Haemoglobin molecules, which consist of four sub-units. Upon digestion, proteins break down into amino acids, which are then reused to synthesize new proteins.

Impact of Damaging Mutations[edit | edit source]

A majority of proteins function as enzymes. Any mutations can impede their efficiency or halt their operation. About 50% of human cancer cases are attributed to mutations in the tumor suppressor p53,[3][4] a protein vital for regulating cell division.[5]

Essential Amino Acids[edit | edit source]

Dietary proteins are indispensable for animals since they cannot synthesize all necessary amino acids. Some amino acids must be derived from food and are termed essential amino acids. Upon digestion, animals convert ingested proteins to free amino acids, which subsequently aid in metabolism and produce necessary enzymes and structures.

Humans require nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.[6] While meats provide all essential amino acids, most plants do not. Consuming a combination of plants, such as wheat and peanut butter or rice and beans, however, offers all the requisite amino acids. Both soy products like tofu and quinoa are comprehensive protein sources.

Jöns Jacob Berzelius, the renowned scientist, was credited with naming proteins,[7] although numerous researchers have contributed to the field of protein study.

See also[edit | edit source]

Other websites[edit | edit source]

  • Protein from the Harvard School of Public Health
Protein Resources

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  1. See protein structure for a detailed exploration of this topic.
  2. For a deeper understanding, consult Translation (genetics) and RNA splicing.
  3. Fersht, Alan 1999. Structure and mechanism in protein sequence. New York: Freeman, p1. ISBN 0716732688
  4. Sidransky D. & Hollstein M. 1996. Annual Review of Medicine 47, p285.
  5. Surget S; Khoury M.P. & Bourdon J.C. 2013. Uncovering the role of p53 splice variants in human malignancy: a clinical perspective. OncoTargets and Therapy. 7: 57–68. [1]
  6. https://medlineplus.gov/ency/article/002222.htm
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