What are three important examples of proteins?

December 12, 2025 •

2 min read

As the workhorses of the cell, proteins perform a vast array of functions vital for life, from providing structural support to enabling biochemical reactions. They are large, complex macromolecules made from smaller units called amino acids.

Quick Summary

This article examines three critical proteins—structural collagen, oxygen-transporting hemoglobin, and catalytic enzymes—detailing their unique functions and importance in biological systems.

Key Points

Structural Support: Collagen is the most abundant protein in the body, providing strength and structure to skin, bones, and connective tissues.
Gas Transport: Hemoglobin, located in red blood cells, is a globular protein that transports oxygen from the lungs to the rest of the body.
Biological Catalysis: Enzymes are proteins that speed up thousands of vital biochemical reactions, such as digestion and metabolism, without being consumed in the process.
Functional Diversity: Proteins exhibit a wide range of functions, from building and repairing tissues (collagen) to transporting molecules (hemoglobin) and catalyzing reactions (enzymes).
Structure Determines Function: The specific three-dimensional shape of each protein, determined by its amino acid sequence, dictates its unique function, as seen in the differences between fibrous collagen and globular hemoglobin.

Proteins are fundamental to the structure, function, and regulation of all living organisms. While thousands of different proteins exist, with each having a unique purpose, some prominent examples stand out for their critical roles. Three particularly important examples are collagen, hemoglobin, and enzymes.

Collagen: The Structural Framework

Collagen is the most abundant protein in the human body, constituting about 30% of its total protein content. This fibrous protein is the primary component of connective tissues, including skin, bones, tendons, ligaments, and cartilage, providing them with structure, strength, and support. Its signature triple helix structure gives it high tensile strength, making it ideal for holding tissues together and withstanding stretching.

The Role of Collagen

Collagen's functions are primarily structural and protective. It helps create the framework for most of the body's tissues and organs. Key functions include providing structure and elasticity to skin, supporting bones and tendons, aiding wound healing, and protecting organs. Natural collagen production declines with age, contributing to wrinkles and joint pain.

Hemoglobin: The Oxygen Transporter

Hemoglobin is a globular protein found in red blood cells that transports oxygen throughout the body. It has four polypeptide chains, each with an iron-containing heme group, allowing it to bind up to four oxygen molecules.

The Mechanism of Oxygen Transport

Oxygen binding to hemoglobin is cooperative; binding one oxygen increases the protein's affinity for more oxygen, making it efficient at picking up oxygen in the lungs and releasing it in oxygen-poor tissues. Hemoglobin also transports some carbon dioxide and helps maintain blood pH.

Enzymes: The Biological Catalysts

Enzymes are proteins that act as biological catalysts, speeding up thousands of chemical reactions essential for life, such as metabolism and digestion. They are highly specific, typically catalyzing only one or a few reactions.

Examples of Digestive Enzymes

Digestive enzymes, produced mainly by the pancreas, break down food molecules. Amylase in saliva and the pancreas breaks down carbohydrates into sugars. Lipase, primarily from the pancreas, breaks down fats into fatty acids and glycerol. Without enzymes, vital metabolic reactions would be too slow to sustain life.

Comparison of Collagen, Hemoglobin, and Enzymes


Feature	Collagen	Hemoglobin	Enzymes (Amylase/Lipase)
Primary Function	Structural support and strength	Oxygen and carbon dioxide transport	Accelerating metabolic reactions
Protein Type	Fibrous	Globular	Globular
Location	Connective tissues (skin, bone, tendons)	Red blood cells	Mouth, stomach, pancreas (digestive enzymes)
Structure	Triple helix; long, fibrous fibers	Four polypeptide chains (tetramer)	Compact, spherical shape with an active site
Solubility	Insoluble	Soluble in aqueous solutions	Soluble in aqueous media

Conclusion

Collagen, hemoglobin, and enzymes exemplify the diverse and crucial roles proteins play in the body. Collagen provides structural integrity, hemoglobin ensures oxygen transport, and enzymes facilitate essential chemical reactions. Their distinct structures and functions highlight the importance of proteins in biological systems and the need for a diet providing essential amino acids.

Learn more about protein function from the National Institutes of Health (NIH).

Frequently Asked Questions

The primary function of collagen is to provide structural support, strength, and elasticity to connective tissues throughout the body, including skin, bones, tendons, and ligaments.

Hemoglobin transports oxygen by binding to it in the lungs via its iron-containing heme groups. It then releases the oxygen to tissues and cells throughout the body where oxygen concentrations are lower.

Enzymes act as biological catalysts to accelerate the chemical reactions that break down food molecules. For example, amylase breaks down starches, while lipase digests fats, allowing for nutrient absorption.

Hemoglobin is a globular protein because it is folded into a compact, spherical shape. This contrasts with fibrous proteins like collagen, which have long, linear, and rope-like structures.

As a person ages, their body's production of collagen naturally decreases. This decline can lead to visible signs of aging like wrinkles, decreased skin elasticity, and an increased risk of joint problems.

Yes, a lack or malfunction of certain enzymes can cause health problems. For instance, pancreatic enzyme insufficiency can lead to digestive issues, and deficiencies can cause specific diseases like phenylketonuria (PKU).

No, proteins are incredibly diverse in their functions. Their specific amino acid sequence and resulting three-dimensional structure determine their unique role, whether it's providing structure, transport, catalysis, or other functions.