Thursday, December 20, 2018
'Ap Biology Notes Cellular Communication Essay\r'
'Cell-to- carrellular telephone communication is all-important(a) in multi prison prison cellular organisms. They must go by to unionize bendivities such as growth and development, and reproduction. In extension unicellular organisms communicate with each other. Signals may part light, or touch scarce we will center on on chemical manoeuvers.\r\n1. External signals atomic number 18 converted to resolutions within the cell a. Evolution of cell sign of the zodiac i. In yeast a cells and ÃÂ±cells both loose chemicals, which bathroom wholly be received by the alternate type yeast. This signals the 2 cells to join via fusion 1. The process by which the signal on the prove of the cell is converted to a series of locomote by the cell in solution is called a signal transduction channel ii. Signal transduction pathways ar rattling similar in yeast and in mixed multicellular organisms 2. This leads scientists to believe that this pathway evolved first in ancient p rokaryotes b. Local and abundant distance signboard iii. Local foretoken\r\n3. Adjacent cells of plants and animals may communicate with cell junctions a. Signaling substances dissolved in the cytol travel between cells i. Plants = plasmodesmata\r\nii. animals = gap junctions\r\n4. Animal cells may accustom the following\r\nb. Cell-to-cell recognition\r\niii. deport contact between tissue layer-bound cell- start shreds iv. Important in immature development and immune reaction\r\nc. Paracrine signaling\r\nv. Uses local regulators which are released and travel only a abruptly distance to nigh cells vi. Ex. Growth factors target nearby cells to grow and divide d. Synaptic signaling\r\nvii. galvanic signal a wide a nerve cell jaunts a chemical release across a synapse to trigger resolution in target cell viii.\r\nEx. Nerve cells\r\niv. Long- distance signaling\r\n5. Both plants and animals use hormones\r\ne. Animals (endocrine signaling) cells release hormones which tra vel in the circulatory corpse to target cells f. Plants hormones travel in vessels or by scattering through with(predicate) the air as sport g. Hormones vary in size and regulate\r\n6. anxious system signals can likewise be long distance c. The three stages of cell signaling: A preview\r\nv. resolution: when the target cell detects a signaling tittle. The signaling molecule binds to a sense organ protein on the target cellÃ¢â¬â¢s surface vi. Transduction: After rachis the sense organ protein is lurchd in or so way, this converts the signal to a image that will contribute about a ad hoc cellular response\r\n7. May occur in a unity step or a series of changes vii. reaction: The transduced signal triggers a peculiar(prenominal) cellular response. 8. catalysis of an enzyme, rearrangement of the cytoskeleton, activation of a specific gene 2. Reception: A signaling molecule binds to a sense organ protein, causing it to change class d. To ensure signals are sent to th e correct cell signaling molecules act as a ligand. viii. Ligand- molecule that specifically binds to some other (normally larger) molecule ix. The receptor protein then usually changes word form x. May be located on the membrane or inside the cell e. Receptors in the germ plasm membrane\r\nxi. Water-soluble signaling molecule binds to receptor on the membrane causing it to change shape or aggregate. f. Intracellular Receptors xii. Found in cytoplasm or nucleus of target cells\r\n9. Signaling molecule must be hydrophobic enough or small enough to pass through the germ plasm membrane h. Steroid hormones, thyroid hormones, nitric oxide | Examples| nerve tract| Other|\r\nG-Protein Coupled Receptors| Yeast mating factors, epinephrine, hormones, neurotransmitters| 1. signaling molecule binds to the g-protein receptor 2. receptor changes shape and the cytoplasmatic side binds to the inactive G protein 3. GTP then displaces to form GDP and activates the protein 4. Activated G protein diffuses along the membrane to an enzyme altering the enzyme to trigger the next step| bacteria such as whooping cough, botulism and cholera disrupt this pathway| Receptor Tyrosine Kinases| Enzymes that catalyze the transfer of inorganic phosphate groups| 1. binding of two signaling molecules to two tyrosine chains causes the two to associate with each other forming a dimer\r\n2. dimerization activates the tyrosine kinase country to add a phosphate from and ATP to each tyrosine in the polypeptide 3. each tail can directly bind to and activate a different specific relay protein within the cell| One receptor may activate ten+ pathways. Absence can result in cancer| Ion Channel Receptors| loathsome system| 1. signaling molecule binds to the ion channel in the membrane 2. protein changes shape creating a channel through the membrane 3. specific ions can now watercourse through the membrane which may cause a change in the cell or trigger another pathway| Some ion gated channels are controlled by change in voltage quite than binding of a ligand|\r\ng. Intracellular Receptors\r\nxiii. Ex. Testosterone\r\n10. Hormone passes through the plasma membrane 11. Testosterone binds to a receptor protein in the cytoplasm activating it 12. The hormone-receptor complex enters the nucleus and binds to a specific gene 13. The bound protein acts as a transcription factor, stimulating the transcription of the gene into template RNA 14. The mRNA is translated into a specific protein 3. Transduction: cascades of molecular(a) interactions relay signals from receptor to target molecules in the cell h. Protein phosphorylation and dephosphorylation\r\nxiv. Proteins can be activated by the accessory of a phosphate group (often broken gain of ATP or GTP) 15. Phosphates are transferred from ATP to a protein by a general group of enzymes cognize as protein kinases i. Phosphorylation often causes the protein to change shape j. This happens because the added phosphate group interact s with polar or charged amino acids within the protein xv. Protein phosphatases are enzymes that remove phosphate groups from a protein 16. Mechanism for turning off signal transduction 17. These also allow for turning off and reusing pathways i. Small molecules and ions as endorsement couriers\r\nxvi. Molecules other than proteins act as second messengers 18. Small and water soluble such as ions\r\nk. This allows them to rapidly spread throughout the cell via diffusion 19. Second messenger refers to anything after the first messenger which is the extracellular signaling molecule that binds to the membrane 20. well-nigh common second messengers are cyclic amp and Ca+2 xvii. Cyclic angstrom unit as a second messenger in response to the hormone epinephrine 21. Epinephrine binds to receptor molecule protein activates adenylyl cyclase which can catalyze the synthesis of numerous molecules of mob l. Adenylyl cyclase catalyzes the conversion of ATP into cAMP ix. cAMP usually activat es a serine/threonine kinase known as protein kinase A which phosphorylates many other proteins m. cAMP is converted back to AMP by phosphodiesterase xviii. Calcium ions and inositol tripohosphate\r\n22. Increasing calcium assimilation causes responses such as muscle contraction, secretion of substances, and cell grade in animals, and greening in response to light in plants 23. Calcium is usually in high concentrations outside of the cell and in the ER but in low concentrations in the cytosol 24. pass\r\nn. Signaling molecule binds to receptor o. Phospholipid pinches off membrane IP3 is released as second messenger p. IP3 binds to receptor on ER causing protein channel to open q. Ca+2 is released into cytosol\r\n4. Response: Cell signaling leads to command of transcription or cytoplasmic activities j. Nuclear and cytoplasmic responses\r\nxix. Pathways lead to the regulation of one or much cellular activities\r\n25. Regulate protein synthesis\r\nr. Turning specific genes on or off (calls for the synthesis of mRNA from DNA)\r\n26. Regulate protein activity\r\ns. Cause a shape change to turn a protein on or off\r\n27. Regulate overall shape change of cell\r\n28. Release of mating factors\r\n29. Cell division\r\nk. Fine-tuning of the response\r\nxx. Signal amplification\r\n30. Enzyme cascades aggrandize effects by increasing the product at each step t. Enzymes stay active long enough to work on multiple products before becoming inactive xxi. The specificity of cell signaling and coordination of the response 31. Different types of cells are programmed to respond to only original types of signals u. Some cells will respond to the same signals but in different ways v. This is because different cells bear different collections of proteins xxii. Signaling efficiency: scaffolding proteins and signaling complexes\r\n32. Scaffolding proteins increase the efficiency of the response w. A large protein with multiple protein kinases attached x. Decreases the time o f the response because diffusion between proteins is not needed 33. Pathways are not linear, in fact the same protein may act in multiple pathways 34. Relay proteins coiffure as branch points where the signal may go in one of two directions xxiii. Termination of the signal\r\n35. Each step in the pathway lasts only a short time, this makes the proteins ready for a hot signal 36. When the signaling molecule leaves leave the receptor it reverts to its inactive form and the relay molecules follow\r\n'