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How do proteins act as structural parts of cells and tissues?

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Peptide — Protein The molecular structure of a peptide (a small protein) consists of a sequence of amino acids.

Proteins serve as essential structural components of cells and tissues by providing mechanical support, maintaining shape, and facilitating tissue integrity. They function primarily through two systems: the intracellular cytoskeleton and the extracellular matrix.12

Intracellular Structure: The Cytoskeleton

Within eukaryotic cells, the cytoskeleton is a complex network of protein filaments that organizes cellular constituents and maintains cell shape. Three primary types of protein filaments perform these roles:3
* Actin filaments: Form meshworks or bundles that determine cell shape and mediate adhesion to substrates.3
* Microtubules: Long, dynamic filaments that provide structural support and facilitate the movement of organelles and chromosomes.3
* Intermediate filaments: Highly stable structures that act as the cell's "skeleton," anchoring the nucleus and providing the elasticity needed to withstand mechanical tension.3

Extracellular Structure: The Matrix

Outside the cell, proteins form the extracellular matrix, a scaffold that binds cells together into tissues.41
* Collagen: The most abundant protein in vertebrates, it forms ropelike fibers with high tensile strength, providing the framework for bones, tendons, ligaments, and skin.456
* Elastin: A cross-linked protein that imparts elasticity to tissues, allowing them to return to their original shape after stretching.45