How do proteins act as hormones?

Proteins act as hormones by binding to specific receptors on target cells, triggering a cascade of biochemical reactions within the cell.

Proteins, including those that function as hormones, are large molecules made up of amino acids. They are synthesised in the body according to the instructions encoded in our DNA. Hormones are chemical messengers that are produced in one part of the body, but act on cells in other parts of the body. Protein hormones, like all hormones, are crucial for maintaining homeostasis and regulating various physiological processes.

Protein hormones work by binding to specific receptors on the surface of target cells. These receptors are proteins themselves, and their shape is complementary to the shape of the hormone. This ensures that each hormone will only bind to its specific receptor, like a key fitting into a lock. This specificity is crucial for the precise regulation of biological processes.

When a protein hormone binds to its receptor, it triggers a cascade of biochemical reactions within the cell. This is often referred to as a signal transduction pathway. The hormone acts as the initial signal, and the reactions that follow amplify this signal, leading to a response within the cell. This response could involve changes in the cell's metabolism, growth, division, or even its death.

For example, insulin is a protein hormone that regulates blood sugar levels. When blood sugar levels rise, insulin is released from the pancreas. It travels through the bloodstream to cells throughout the body, where it binds to insulin receptors on the cell surface. This triggers a series of reactions within the cell that result in the uptake of glucose from the blood, thereby lowering blood sugar levels.

In summary, proteins can act as hormones by binding to specific receptors on target cells, triggering a series of biochemical reactions that lead to a response within the cell. This mechanism allows protein hormones to regulate a wide range of physiological processes, from metabolism to growth and development.