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Amino acids

Amino acids

Amino acids are the monomers that comprise proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom, or the alpha (α) carbon, bonded to an amino group (NH2), a carboxyl group (COOH), and to a hydrogen atom. Every amino acid also has another atom or group of atoms bonded to the central atom known as the R group. There are 20 common amino acids present in proteins, each with a different R group. Variation in the amino acid sequence is responsible for...

What are Proteins?

What are Proteins?

Proteins are polymers of amino acids linked together by peptide bonds. Proteins and polypeptides are interchangeably used to refer to long chains of amino acids. However, polypeptides have a molecular weight of fewer than 10,000 daltons, while proteins have greater molecular weight. Polypeptides with less than 20 amino acids are called oligopeptides or simply peptides. Interactions among the constituent amino acid side chains of proteins help them fold into a stable 3-dimensional structure...

What are Proteins?

What are Proteins?

What are Proteins?

What are Proteins?

Proteins are polymers of amino acids linked together by peptide bonds. Proteins and polypeptides are interchangeably used to refer to long chains of amino acids. However, polypeptides have a molecular weight of fewer than 10,000 daltons, while proteins have greater molecular weight. Polypeptides with less than 20 amino acids are called oligopeptides or simply peptides. Interactions among the constituent amino acid side chains of proteins help them fold into a stable 3-dimensional structure...

What are Proteins?

What are Proteins?

Protein Organization

Protein Organization

Proteins are polymers of amino acid residues. They are versatile and responsible for different cellular functions, including DNA replication, molecular transport, catalysis, and structural support. Proteins have a hierarchical structure comprising at least three levels of organization: primary, secondary, and tertiary structure. Some large proteins have a quaternary structure where individual protein subunits are linked together.
The primary structure of a protein is its amino acid sequence.

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Related Experiment Video

Updated: Jun 17, 2026

Residue-Specific Exchange of Proline by Proline Analogs in Fluorescent Proteins: How "Molecular Surgery" of the Backbone Affects Folding and Stability

Residue-Specific Exchange of Proline by Proline Analogs in Fluorescent Proteins: How "Molecular Surgery" of the Backbone Affects Folding and Stability

Published on: February 3, 2022

Proline: a multifunctional amino acid.

László Szabados¹, Arnould Savouré

¹Institute of Plant Biology, Biological Research Center, Temesvári krt. 62., H-6726 Szeged, Hungary. szabados@brc.hu

Trends in Plant Science

|December 29, 2009

Summary

Plants accumulate proline under stress. This amino acid aids cellular balance, signaling, and recovery, offering potential for engineering stress-tolerant crops.

Area of Science:

Plant Physiology
Biochemistry
Molecular Biology

Background:

Proline accumulation is a common plant response to environmental stress.
While proline metabolism is understood, its precise biological functions remain partially unclear.

Purpose of the Study:

To review the compartmentalization of proline metabolism (biosynthesis, accumulation, degradation) in plant cells.
To discuss the roles of proline in cellular homeostasis, signaling, and stress recovery.

Main Methods:

Literature review and synthesis of existing research on proline metabolism and function.
Discussion of proline's roles in cellular compartments like cytosol, chloroplasts, and mitochondria.

Main Results:

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Proline is compartmentalized in cytosol, chloroplasts, and mitochondria.

Proline contributes to redox balance, energy status, and acts as a signaling molecule.

Proline signaling influences mitochondrial function, cell proliferation/death, and gene expression for stress recovery.

Conclusions:

Proline's functions in cellular homeostasis and signaling are crucial for plant stress response.
Further understanding of proline regulation and function can guide engineering for improved plant stress tolerance.