Receptors are protein molecules that recognize and respond to the body’s own (endogenous) chemical messengers, such as hormones or neurotransmitters. Drug molecules may combine with receptors to initiate a series of physiological and biochemical changes. Receptor-mediated drug effects involve two distinct processes:

The presence of receptors for the hormones estrogen and progesterone is also determined, because these receptors play an important role in the cancer’s development and in decisions regarding the appropriate treatment.

…four groups—growth factors, growth factor receptors, signal transducers, and nuclear regulatory proteins (transcription factors). For a stimulatory signal to reach the nucleus and “turn on” cell division, four main steps must occur. First, a growth factor must bind to its receptor on the cell membrane. Second, the receptor must become…

…commonly involves specific proteins called receptors that are embedded in the cell membrane.

The ability of a cell to respond to an extracellular signal depends on the presence of specific proteins called receptors, which are located on the cell surface or in the cytoplasm. Receptors bind chemical signals that ultimately trigger a mechanism to modify the behavior…

…and activating specific molecules called receptors. Receptors are found on the surface of target cells in the case of protein and peptide hormones, or they are found within the cytoplasm or nuclei of target cells in the case of steroid hormones and thyroid hormones. Each receptor has a strong, highly…

Lymphocytes are distinguished from other cells by their capacity to recognize foreign molecules. Recognition is accomplished by means of receptor molecules. A receptor molecule is a special protein whose shape is complementary to a portion of a foreign molecule. This complementarity of shape…

Upon reaching their target organs by traveling with the blood vessels that supply them, sympathetic fibers terminate as a series of swellings close to the end organ. Because of this anatomical arrangement, autonomic transmission takes place across a junction rather than a synapse. “Presynaptic”…

…and peripheral nervous system have receptor proteins on their surfaces to which nicotine binds, much in the way that a key fits into a lock. When a molecule of nicotine binds to a nicotine receptor, it causes the neuron to transmit a nerve impulse to various target organs and tissues.…