BIOLOGY_111_Lecture_5-Receptors.

BIOLOGY_111_Lecture_5-Receptors. - BIOLOGY 111 Lecture...

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BIOLOGY 111 Lecture 5-Receptors Cell Communication -Cells must interact with their environment. -Cells in multicellular organisms must coordinate activities. -Act as a single unit: a tissue or an organ. -Communication between cells require: -Ligand: the signaling molecule. -Receptor protein: the molecule to which the receptor binds. -Ligand-receptor binding conveys information. -Causes a response through signal transduction. FIGURE 9.1 Four Mechanisms -There are four basic mechanisms for cellular communication: 1. Direct contact. 2. Paracrine signaling. 3. Endocrine signaling. 4. Synaptic signaling. -Can allow the communication to be localized or throughout the system as a whole. Direct Contact -Molecules on the surface of one cell are recognized by receptors on the adjacent cell. -The signaling molecule is passed from one cell to another and the cells are touching. FIGURE 9.2 Paracrine Signaling -Signal released from a cell has an effect on neighboring cells. -Signals sent and received around a very small area. -Ex: a cut on your finger. The body needs to fix the cut, but only the cells around the cut, not the whole body. FIGURE 9.2 Endocrine Signaling -Hormones released from a cell effects other cells throughout the body. -Affects any cell that has the receptor in the body. -Can travel a great distance, throughout the whole body. -Ex: a viral infection, all cells would have to be on the lookout to defend themselves from the virus. FIGURE 9.2 Synaptic Signaling -Nerve cells release the signal (neurotransmitter) which binds receptors on nearby cells. -A really small distance is traveled. -Only used in the nervous system, on the nerve cells and the cells they are involved with. FIGURE 9.2
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Signal Transduction -When a Ligand binds to a receptor protein, the cell responds. -Signal transduction: the events within the cell that occur in response to a signal. -Transmitting & relaying the signal (to the proteins to cause the change). -Controls or alters flow of information in the cell (these signals trigger the transcription factors). -Controls activities in the cell. -Growth, maturation, production, metabolism, death (what the cell is doing, is it ready for apoptosis, etc. It signals for changes in cells). -Different cell types can respond differently to the same signal. Cellular Responses -A cell’s response to a signal often involves activating or inactivating proteins. -Phosphorylation is a common way to change the activity of a protein. -Cleavage of a signal peptide can activate a protein.
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