1. Catalysis: Proteins act as enzymes, which are biological catalysts. They speed up chemical reactions in cells without being consumed themselves. Enzymes are highly specific, meaning each enzyme catalyzes a particular reaction. Here's a breakdown:

* How it works: Enzymes lower the activation energy of a reaction, making it easier for the reaction to occur. They do this by providing an alternative reaction pathway that requires less energy.

* Examples:

* DNA polymerase: This enzyme is involved in DNA replication, where it copies DNA to create new strands.

* Lactase: This enzyme breaks down lactose, a sugar found in milk.

* Pepsin: This enzyme breaks down proteins in the stomach.

2. Structure and Support: Proteins provide structural support and shape to cells, tissues, and organs. They are the building blocks of many cellular components. Here's a breakdown:

* How it works: Proteins can form fibers, sheets, or other complex structures. They can interact with other molecules to build complex assemblies.

* Examples:

* Collagen: This fibrous protein is the most abundant protein in the human body. It provides strength and flexibility to skin, bones, tendons, and ligaments.

* Keratin: This fibrous protein is found in hair, nails, and skin. It provides protection and structure.

* Tubulin: This protein forms microtubules, which are important for cell division, intracellular transport, and maintaining cell shape.

These are just two examples of the many vital processes that proteins carry out. Their diverse functions are essential for life and make them one of the most important classes of biological molecules.