Pure proteins are large, complex molecules that are essential for the structure and function of all living cells. Peptides are smaller molecules consisting of two or more amino acids linked together by chemical bonds. Proteins consist of hundreds or even thousands of amino acids, while peptides typically contain only a few amino acids. You can find peptides in all living cells, but they are not as abundant as proteins. Peptides typically have specific functions within the cell, such as acting as hormones or enzymes. On the other hand, proteins can have a wide variety of functions, including providing structure and support, transporting molecules, and catalyzing chemical reactions. Peptides are usually much less stable than proteins and can be broken down by enzymes. High quality proteins are generally more stable and can withstand harsh conditions, such as extreme temperatures or acidity. Because of their stability, proteins can be stored in the body for long periods of time and used when needed. On the other hand, Peptides are typically used only when needed and then broken down and excreted. Another main difference between protein and peptide is that proteins are the main component of muscles, organs, and skin. You can find peptides in all body tissues, but they are especially abundant in the brain and other nervous tissue. Peptides play important roles in cell signaling and communication. They are also involved in immune response and metabolism regulation. Peptides are sometimes referred to as "signaling molecules" because they can bind to receptors on cells and alter the activity of those cells. Peptides can also be used to transport drugs or other molecules into cells.