What are the classes of endocytic activities seen in animal cells and in general how do they differ What about any such activities in prokaryotic cells phagocytosis engulf particle using pseudophobia and enclosing it in vacuole specific cell surface determines uptake pinocytosis vesicles spontaneously and constitutively form smaller scale than phagocytosis receptor mediated endocytosis plasma membrane contains coated pits that bind extracellular molecules ex hormone reuptake Outline the typical fate of a bacterium internalized by a macrophage blue pathway early endosome secretory vesicle late endosome golgi ER green pathway early endosome late endosome lysosome digests vesicle contents red pathway ER golgi secretory vesicle late endosome lysosome early endosome late endosome lysosome there is a lot of traffic of these vesicles theme is that they moved because they are attached to motor proteins on microtubules part of specificity of vesicle direction is determined by the types of snares it may have these snares provide adapters that link vesicles to target membrane What are lysosomes What are the properties of their enzymes List five lysosomal enzymes and indicate the classes of substrates they act upon and the reactions they would catalyze membrane surrounded compartments hydrolytic enzymes within degarde internalized mat will not degrade each other or membranes work in optimal pH of 5 4 acidic and is protective in case contents leak out into cell which has pH of 7 2 enzymes will be sluggish and not cause accidental damage ATP is used to pump in H and make acidic pH nuclease break down nuclear membrane protease general protein digestion glycosidase breaks down bond between a sugar alcohol or sugar sugar lipases breaks down fats phosphatases removes a phosphate group sulphatases break down sulfate ester bond phospholipases break down phospholipids Give an example of a lysosomal disorder by indicating the nature of the deficit and the resulting outcome lysosome degrade matrix between cells and cartilage needed for development when the cells and tissues must be remodeled Hurler s syndrome lacks a lysosomal enzyme infant inherited 2 defective genes from parents alpha L iduronidase deficiency cannot degrade dermatan and heparan sulphate which must occur for proper developmental processes enlarged liver gargoyle like features heart failure mental retardation short life span Give examples of specific pathogens that block their own neutralizations in human hosts and manage to evade the host s immune responses Describe what happens in each case Outline the events involved in the uptake of iron and of LDL from the circulation by receptor mediated endocytosis You should include the details on how the ligands get internalized into cells and the proteins involved and their fates receptor mediated endocytosis in cholesterol is a disorder that leads to elevation in cholesterol levels involves problems with LDL receptor so that the receptor cannot aggregate at these sites uptake of iron iron is needed for oxygen binding in hemoglobin heme is associated with iron iron is needed in many cells but is very toxic 1 iron binds to transferrin Tf a small protein in circulation 2 Tf with attached iron bind to TfR receptor on plasma membrane pH 7 2 3 TfR iron Tf are engulfed by receptor mediated endocytosis via coated pits 4 internalized into vesicles move to the early endosome pH 5 5 due to proton pump 5 iron loses its affinity to Tf due to pH changes 6 iron is reduced from Fe III Fe II 7 Tf and TfR go into recycling endosome to be released to the plasma membrane 8 reduced iron is used in cell hemoglobin or ferritin Describe the composition of the coat on coated vesicles and pits involved in endocytic activities triskelion clathrin adaptin receptors ligands and the orientations of these components in the membranes coated pit picks up substances neck region forms and buds off use surface protein to trap ligands peripheral proteins are swept into the sinks and are internalized into vesicle two types of receptors and ligands 1 housekeeping receptors proteins on cell surface that bring substances that cells require ex pick up iron receptors are saved and recycled to membrane 2 signaling receptors hormones responses may only be needed for a certain time and may be degraded after use tryskelion 3 legged structure each tryskelion is clathrin protein made of 3 heavy and 3 light chains polyhedral structures in coated vesicles leg of one interacts with leg of other to form this coat clathrin will spontaneously form these coats low energy state 2 molecule types heavy chains 180 000 dalton and light chains 25 000 dalton big variety of triskelions in different vesicles adaptin anchor clathrin to membrane Ap1 2 3 etc focus on Ap2 found in plasma membrane other forms found in golgi Ap1 subunits alpha beta mu and sigma beta subunit anchors clathrin to membrane alpha subunit is shown by this ear on other side binds accessory proteins that add to curvature of the protein receptor being attached to coated vesicles typically has cytoplasmic segment that will bind to adaptor protein which holds it in place What is the role of dynamin in vesicle budding How does the presence of gamma S GTP affect the action of the protein dynamin assembled at site where membranes are budding for coated vesicles different types of dynamin help when cell is dividing by splitting mitochondria energy comes from GTP helical structure around neck which gets thinner and eventually buds off as GTP is used if GTP is there it is hydrolyzed if GTP gamma S sulfur instead of phosphate then cannot be hydrolyzed by dynamin so it freezes the dynamin structure continuous helices of dynamin elongated Give is the composition of LDL particles Be specific and detailed LDL monolayer of phospholipid and cholesterol molecules core of the LDL consists of cholesterol with attached fatty acids and 1 molecule of protein apoB100 Describe the endosomal compartments and outline some of the activities associated with the sorting and intracellular digestions that take place in those compartments give examples from LDL uptake cholesterol is very insoluble so must be packaged in particle low or high density lipoprotein in animal cells plasma membrane in nucleus for production of steroid hormones when cholesterol levels are low in cell cell can make cholesterol from scratch genetic expression of LDL receptors on tissue to pick up LDL from blood 1 LDL receptor and LDL is
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