Lecture 1: Cell Communication PDF

Lecture 1 Presented by Dr/Shimaa Ali Abass  Overview Mode of cellular communication Intracellular receptors Cell surface receptors Mode of cell communication  Cell communication definition Any of several ways in which living cells of an organism communicate with one an...

Lecture 1 Presented by Dr/Shimaa Ali Abass  Overview Mode of cellular communication Intracellular receptors Cell surface receptors Mode of cell communication  Cell communication definition Any of several ways in which living cells of an organism communicate with one another, whether by direct contact between cells or by means of chemical signals carried by neurotransmitter substances, hormones, and cyclic AMP. Mode of cell communication Contant-dependent Paracrine Autocrine Endocrine  Contant-dependent Occur when surface molecules on one membrane bind to surface molecules on another cell membrane. Require direct membrane- membrane contact.  Paracrine cell communication In paracrine signaling the signaling molecule affects only target cells in the proximity of the signaling cell. An example is the conduction of an electric signal from one nerve cell to another or to a muscle cell. In this case the signaling molecule is a neurotransmitter.  Synaptic cell communication Synaptic signalling is performed by neurons that transmit signals electrically along their axons and release neurotransmitters at synapses, which are often located far away from the neuronal cell body  Autocrine cell communication In autocrine signaling cells respond to molecules they produce themselves. Examples include many growth factors. Prostaglandines, lipophilic hormones that bind to membrane receptors, are often used in paracrine and autocrine signaling. They generally modulate the effect of other hormones. Autocrine cell communication  Endocrine cell communication In endocrine signaling hormones are produce by an endocrine gland and sent through the blood stream to distant cells. Types of cell communication Binding of extracellular signal molecules to receptors  Intracellular receptors The signaling molecules must be hydrophobic molecules that are able to diffuse through the membrane Polar molecules (e.g. hormones) cannot cross the membrane rapidly enough and must bind to a plasma membrane receptor Cell surface receptor  Cell surface receptor Most signal molecules are hydrophilic and are therefore unable to cross the target cell membrane directly They bind to cell-surface receptors, which in turn generate signal in the target cell.  Hormones They are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, skin, muscles and other tissues.  The lipid soluble hormones They can easily passes through the plasma membrane. They have their receptor inside the cell, freely floating in the cytoplasm. Binding of hormone to the specific receptor activates the enzymatic activity of the cell for biochemical changes.  The lipid soluble hormones Some hormones (testosterone, progesterone, estrogen, cortisol, thyroxine) have their receptor localized inside the nucleus, the hormone-receptor complex are carried inside the nucleus. The hormone-receptor complex initiate transcription of the DNA to form specific mRNA. mRNA initiate protein synthesis in the cytoplasm.  Hydrophillic hormones They bind to specific receptor proteins on the surface of the target cells They influence and do not enter the cystol or nucleus. The cell-surface receptors act as signal transducers by converting an extracellular ligand-binding event into intracellular signals that alter the behavior of target cells.