2) Cell to Cell Communication
2) Cell to Cell Communication
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This 4 page Class Notes was uploaded by Andrea Starkman on Tuesday February 9, 2016. The Class Notes belongs to at George Washington University taught by Dr. Randall Packer in Spring 2016. Since its upload, it has received 16 views. For similar materials see Human Phisiology in Biological Sciences at George Washington University.
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Date Created: 02/09/16
(2) Cell to Cell Communication 01/20/2016 ▯ Phagocytosis: Cell Eating. Macrophage: Nucleated and eats other cells. Have receptors that respond to carbohydrates in cell wall of bacteria or substances released when body cells break apart. Clean up the mess and recycles the material. First line of defense for infection. o General Chemotaxis: Responding/sensitive to certain kinds of chemicals. This starts the process of phagocytosis. o Pseudopods: Extend from the macrophage. Fuse and form a membrane bound vacuole with the bacteria inside. o Enzymes fuse with the vacuole and break up/kill the bacteria. ▯ ▯ Pinocytosis (Endocytosis): Losing membrane to the interior so has to recycle its cell membrane. Receptors: on the cell membrane and used to recognize ligand (s). Usually recycled back out to the membrane. Ligand: Always in a solution. Binds to the receptor which then recognizes it. Protein Invagination of the membrane: When the ligand binds to the receptor. This then seals off. Vesicle Formation: Smaller vesicle rather than a vacuole. It holds the ligand inside. Can fuse with lysosome whose enzymes break down the ligand. ▯ ▯ Exocytosis: Something is produced out of golgi apparatus in a vesicle. Could be a protein. Adding membrane to the cell. Vesicle: Migrates to the cell membrane to its specific docking point. It then opens up to the exterior allowing the protein to be released into the environment. Coded Pit: The empty vesicles are collected together and recycled back into the interior of the cell. Pancreas beta cells secrete insulin using this technique. ▯ ▯ WITHIN THE TISSUE: ▯ Endocrine and Nervous System: Rely on chemical signaling to communicate with each other. Difference is the distance through wich the chemicals are ▯ ▯ Gap Junctions: Chemical pass directly from one cell to another. Proteins in the cell membranes create an open pore between the two cytoplasms. Cardiac and visceral smooth muscle. Communication electrical potential differences. ▯ ▯ Contact dependent: Receptor binds to protein (glycol) expressed on outside of other cell. Hooking up sends a signal. Immune system (macrophage) ▯ ▯ Autocrins: Released chemical actins on a receptor on the cell itself. Communicated through interstitial fluid (within the tissue) ▯ Paracrine: Released chemical stimulates receptor on a neighboring cell. Communicated through interstitial fluid (within the tissue) ▯ ▯ WHOLE BODY: ▯ Hormones: Long distance cell communication. Go through the bloodstream throughout the body ▯ ▯ Target Cells: Have specific receptors for particular hormones. Only the cells with the correct receptor will respond. ▯ ▯ Neurohormone: Cell secreting is a modified neuron rather than traditional endocrine cell. Starts out as a neuron and turns into secretory. Neurotransmitter binds to cell membrane of receiving cell (usually another neuron or muscle cell). Hormones go through synaptic cleft (gap). Posterior pituitary. ▯ ▯ SIGNAL AMPLIFICATION: When hit a target cell the signal becomes significantly amplified. - Signal Transduction Pathways: Receptors bind the ligand(s) and the number of receptors are also regulated by the cells. Is the receptor there and how many are there. Can respond more strongly at one time and less at another. ▯ ▯ Ligand Gated Ion Channels: Ligand binds to a receptor and opens the previously closed channel allowing mineral ions (NA+, K+, CL-) to flow in and out of the cell down the concentration gradient. Fastest ▯ ▯ Tyrosine Kinase Receptor: Channel has the receptor. Ligand binds to specific receptor site. Activates tyrosine kinase activity in that area of the protein. Proteins with kerosene residue, the enzyme phosphorolates. Resulting in activation of an enzyme. ▯ G Protein Coupled Receptors: Receptor is connected to a G protein. When inactive has a bound GDP. 1) When ligand binds to receptor the GDP is replaced by GTP and G proteins dissociate. One of the Alpha G proteins binds to a receptor in an ion channel in another portion of the cell. o Takes longer than when there is direct control of the ligand but has a greater amplification effect and channels stay open longer. o G proteins: Alpha, Beta, Gama. o Only carries information if the signal varies, otherwise its only on or off. The frequency and amplitude is what is studied in the signals. 2) Adenyl cyclase converts ATP into cAMP. Signaling cascade then activates another enzyme (PKA) which phosphorolates different kinds of proteins. (This activates the protein enzymes. One ligand results in lots of cAMP resulting is phosphorolation of target proteins inside the cell amplifying everything.) o Phosphodiasporase: Knock off phosphate from protein. Inhibited by caffeine. 3) Phospholipid C activated, its enzyme that breaks down lipids. PIP2 breaks down into DAG hydrophobic portion (inside membrane) that activates PKC and into IP3 less hydrophobic that then leaves the cell (fairly polar so can dissolve in cytoplasm). IP3 binds receptors in membrane bound calcium storage sites and calcium is released. Intercellular fluid calcium concentration spikes. o Usually intercellular calcium levels are low but when they increase dramatic events can occur such as muscle contractions. ▯ ▯ Contact dependent integrin receptors: Receptors are attached to cellular cytoskeleton and seem to connect the two. Could affect both or just one of the cells. Intergrins: Proteins attached to the cytoskeleton. Can cause changes in cell shape. ▯ ▯ Steroids: Derived from cholesterol and built on Cyclopantano(…..) They are usually hydrophobic. Able to cross some membranes with ease. Travel through the blood bound loosely to plasma proteins (transport protein), there is a dissociation between the two. ▯ Estrogen enters the cell and there are receptors inside the cell. Only attaches to the dissociated protein. Binds its way into the nucleus using hormone receptor complex. This binds to Hormone Response Element (HRE) (part of the DNA). Step in initiation of transcription, enzymes working to produce mRNA. ▯ ▯ CONTROL SYSTEMS: ▯ ▯ Tonic: Regulate by changing frequency of signals. Few signals results in little to no contraction (norepinephrine level low). Increased frequency of signaling causes constriction of blood vessels (increased blood pressure, cortisol levels, decreased blood flow in skin). ▯ ▯ Antagonistic: Opposing forces to control mechanism. ▯ Sympathetic Neurons: Release epinephrine and increase heart rate and force of contraction. ▯ Parasympathetic: Heart rate slows. ▯ ▯ ▯
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