Definition of protein
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Definition of Protein: A Comprehensive Overview
Protein Structure and Hierarchy
Indexed String of Elements in Protein Structures
Proteins are complex molecules defined as indexed strings of elements at various hierarchical levels, including sequence, secondary structure, and super-secondary structure. These elements, such as residues or secondary structure segments like helices and beta-strands, possess specific properties and engage in relationships with other elements. This hierarchical organization allows for the computation of element-by-element dissimilarity matrices, which are crucial for alignment procedures and exploring protein structure variability .
Evolution of the Term "Protein"
Historical Context and Modern Understanding
The term "protein" has evolved significantly since its inception. Initially coined in 1838 by Mulder, based on a suggestion from Berzelius, the word "protein" was derived from the Greek adjective meaning "of the first rank or position." This term was used to describe a complex radical believed to be combined with sulfur and phosphorus in natural proteins 67. Over time, the understanding of proteins has expanded, revealing their overwhelming heterogeneity in size, shape, chemistry, and function. Modern biologists recognize that the term encompasses a diverse group of macromolecules essential for life, challenging the early, more simplistic definitions .
Biological Roles and Functions of Proteins
Versatile Polymers in Cellular Functions
Proteins are essential and versatile polymers composed of sequenced amino acids, which often form organized three-dimensional structures. These structures determine their biological roles, including enzymatic catalysis, genetic information decoding, cell recognition, signaling, and substance transport. Proteins are involved in regulating both intra- and extracellular conditions, highlighting their critical role in cellular function .
Structural and Functional Diversity
Proteins play a variety of roles within cells, such as providing structural support (e.g., cytoskeleton), enabling mechanical functions (e.g., muscle contraction), facilitating biochemical reactions (e.g., enzymes), and participating in cell signaling (e.g., hormones). This diversity underscores the importance of proteins in maintaining cellular integrity and function .
Nutritional and Technological Importance
Essential Macronutrient in Diet
Proteins are a key structural component of many foods and an essential macronutrient in the human diet. The nutritional and technological properties of food proteins depend on their source, extraction, purification, and modification during food manufacture. Additionally, the interactions of proteins with other food components play a significant role in their functionality and sustainability .
Conclusion
Proteins are fundamental to life, serving a multitude of structural, functional, and nutritional roles. From their hierarchical structure and historical origins to their diverse biological functions and importance in diet, proteins represent a complex and essential class of macromolecules. Understanding the full potential and heterogeneity of proteins is crucial for advancing biological research and applications.
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