1. Enzymes: Proteins act as catalysts, speeding up biochemical reactions essential for life. These reactions include everything from breaking down food to building complex molecules. Examples include DNA polymerase (replicating DNA) and lactase (breaking down lactose).
2. Structural components: Proteins provide shape and support to cells and tissues. Examples include collagen (found in skin, tendons, and bones), keratin (found in hair, nails, and skin), and tubulin (forming microtubules in the cytoskeleton).
3. Signal transduction: Proteins act as messengers, relaying information between different parts of the cell or between cells. This allows cells to respond to changes in their environment, communicate with each other, and coordinate their activities. Examples include insulin receptor (responding to insulin signals) and growth hormone receptor (mediating growth).
