Term
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Definition
| membrane-enclosed compartments associated with endocytotic pathways. They are restricted to a portion of the cytoplasm near the cell membrane where vesicles originating from the cell membrane fuse. It has a slightly more acidic environment (pH 6.2 to 6.5) than the cytoplasm. |
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Term
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Definition
| Late endosomes are found near the Golgi and nucleus. They are more acidic, usually pH 5.5 |
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Term
| how substances are transported between the early and late endosomes |
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Definition
| via multivesicular bodies |
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Term
| role of M6P and its receptor in sorting to peroxisome |
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Definition
| M6P is added to the surface of prohydrolase enzymes and acts as a target for M6P receptor. M6P receptors are found in early and late endosomes, lysosomes and the Golgi. The Golgi sends the prohydrolases to endosomes. The acidic environment of the late endosomes causes the release of prohydrolases from the M6P receptors. |
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Term
| why are late endosomes called pre-lysosomes |
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Definition
| because they can turn into lysosomes |
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Term
| how do early endosomes sort proteins |
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Definition
| sort proteins that have been internalized by endocytosis via localized changes in pH |
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Term
| Compartment of Uncoupling Receptor and Ligands (CURLs) |
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Definition
| Another word for early endosome |
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Term
| contents and function of lysosomes |
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Definition
| Lysosomes are digestive organelles that are rich in hydrolytic enzymes, such as proteases, nucleases, glycosidases, lipases and phospholipases. They have a unique membrane that is resistant to hydrolytic digestion. |
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Term
| differences between primary and secondary lysosomes in function and EM |
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Definition
| primary lysosomes are newly formed and and are only solid color in EM. Secondary lysosomes occur when primary lysosomes swallow a substance to be hydrolyzed and have dark clumps within them on EM |
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Term
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Definition
| kills malarial parasites by raising the pH of lysosomes, inactivating many lysosomal enzymes, which interferes with digestive processes |
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Term
| Constitutive secretory pathway of targeting lysosomal membrane proteins to lysosome |
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Definition
| lysosomal integral membrane proteins exit the Golgi in coated vesicles and are delivered to the cell surface. Here, they are endocytosed and, via early and late endosomes, reach the lysosomes |
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Term
| Golgi-derived coated vesicle pathway of targeting lysosomal membrane proteins to lysosome |
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Definition
| the membrane proteins exit the Golgi in clathrin-coated vesicles. They travel and fuse with late endosomes |
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Term
| why lysosomal membrane proteins are not digested by lysosomal enzymes. |
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Definition
| because sugar molecules cover almost the entire luminal surface of these proteins. This protects them from digestion. |
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Term
| names of the three pathways for delivery of substances to lysosome for digestion |
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Definition
| using phagosome, using receptor-mediated endocytosis or pinocytosis, autophagy |
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Term
| delivery of substances to the lysosome for digestion using phagosomes |
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Definition
| Extracellular large particles are phagocytosed. A phagosome, with the material internalized within the cytoplasm, receives hydrolytic enzymes to become a late endosome, which matures into a lysosome |
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Term
| delivery of substances to lysosome for digestion using pinocytosis or receptor-mediated endocytosis |
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Definition
| Small extracellular particles are internalized by pinocytosis and receptor-mediated endocytosis. They follow the endocytotic pathway through early and late endosomal compartments and are finally degraded in lysosomes |
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Term
| delivery of substances to lysosome for digestion using macroautophagy |
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Definition
| In macroautophagy, a portion of the cytoplasm or an entire organelle is first surrounded by a double or multilamellar intracellular membrane of ER to form a vacuole called an autophagosome. After delivery of lysosomal enzymes, the autophagosome matures into a lysosome. The isolation membrane disintegrates within the hydrolytic compartment of the lysosome. |
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Term
| delivery of substances to lysosome for digestion using microautophagy |
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Definition
| In microphagy, cytoplasmic proteins are degraded in a slow, continuous process under normal physiologic conditions. Small cytoplasmic soluble proteins are internalized into lysosomes by invagination of the lysosomal membrane. |
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Term
| List two cell types that secrete lysosomal contents into the extracellular space |
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Definition
| Osteoclasts and neutrophils release lysosomal enzymes directly into the extracellular space to digest components of the extracellular matrix. |
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Term
| Lysosomal storage diseases |
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Definition
| Lysosomal storage diseases are caused by the absence of certain lysosomal enzymes, which causes the patholoic accumulation of undigested substrate in residual bodies. |
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Term
| Appearance and function of peroxisomes |
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Definition
| Peroxisomes are single spherical, membrane-bound organelles. They contain oxidative enzymes. Catalase present in peroxisomes breaks down hydrogen peroxide. Peroxisomes also are responsible for β–oxidation of fatty acids. Peroxisomes in hepatocytes convert alcohol to acetaldehyde. |
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Term
| Explain what is produced by the oxidation that occurs in peroxisomes. Name the enzyme in peroxisomes that breaks down the substance produced by oxidation |
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Definition
| Hydrogen peroxide is produced in most oxidation reactions and is broken down by catalase in peroxisomes. |
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Term
| Generation and targeting of peroxisomal enzymes |
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Definition
| Peroxisomal enzymes are synthesized on cytoplasmic ribosomes and are imported into the peroxisome via peroxisomal targeting signal (Ser-Lys-Leu) attached to its carboxy-terminus |
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Term
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Definition
| Zellweger syndrome is when peroxisomes lose their ability to function because of a lack of necessary enzymes. It is caused by a mutation in the gene encoding the receptor for peroxisome targeting signal so that it does not recognize the signal Ser-Lys-Leu at the carboxy terminus of enzymes directed to peroxisomes |
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Term
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Definition
| Lipofuscin is a brownish-gold pigment visible in H&E staining that accumulates during the years as a result of aging. It is a conglomerate of oxidized lipids, phospholipids, metals and organic molecules |
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Term
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Definition
| Hemosiderin is an iron-storage complex found in the cytoplasm. It is visible in light microscopy as a deep brown granule and is basically indistinguishable from lipfuscin. |
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Term
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Definition
| Glycogen is a branched polymer used as the storage material for glucose. It is not stained in H&E, but can be seen by PAS and also appears in EM as clusters of granules that occupy significant portions of the cytoplasm. |
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Term
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Definition
| droplets are usually extracted by organic solvents used to prepare tissue for EM and light microscopy. Fat droplets in light microscopy are actually holes in the cytoplasm wehere the lipid had been extracted. |
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