Biological processes require communication between cells and between individuals. In all kinds of living organisms, this communication begins at the molecular level. Small signaling molecules (proteins, amino acids, steroids, and other substances) are the messages that pass from one cell to the next; large protein receptors are the receivers of the message. Receptors bind the smaller molecules much as a lock receives a key or a glove receives a hand . Other proteins in the cell membrane associated with the receptors convey the message to the interior of the cell.
Very few biochemical or physiological functions in our bodies are not somehow touched by these molecules or by the process of cellular communication. Here are some examples of how receptors are involved in a variety of biological processes:
• Spermand eggmeet, recognize each other, and bind by a receptor mechanism.
• Embryos develop by cell communication: one cell releases a hormone that binds to a receptor on another cell, and the second cell changes its shape and function, initiating the process of differentiation.
• Hormone-like neurotransmitters are released from one cell (a nerve) and bind to receptors on the surface of a nearby cell (another nerve or a muscle) to cause thought or movement.
• The digestive system propels food and releases enzymes according to the binding of hormones to cells lining the digestive tract.
• Immune system cells contain on their surfaces receptors that are able to recognize foreign proteins and attack invading cells.
• Diseases often act by subverting normal receptor function.
This introductory chapter covers general concepts of communication and how chemical communication compares with human communication; how evolution applies to receptor molecules; and how a pure chemical entity such as a receptor can initiate such large-scale functions as thought.
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|July 2, 2016|
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