lysosomes
- Created by: Amber Manley
- Created on: 13-01-14 14:44
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- Lysosomes
- Function
- major source of intracellular digestion
- cotain 40 hydrolytic enzymes e.g. proteases, nucleases
- acid hydrolases
- protected from own attack
- membrane keeps enzymes out of cytosol
- acid hydolases don't work at cellular pH 7.2
- membrane bound organelle
- pH of 5 is maintained by H+ pump in the membrane
- uses ATP
- pH of 5 is maintained by H+ pump in the membrane
- How
- enzymes are transported from ER where they were synthesised
- digestion products are transported out of the lysosome by transporters in the membrane
- acid hydrolases protected from digestion by high level of glycosylation
- transport of hydrolases
- signal peptide directs synthesis of lysosomal protein to the ER
- N-linked glycosylation
- signal patch directs phosphorylation of terminal mannose
- M6P binds to receptors on hydrolases (luminal)
- also to adaptin on the cytosol side
- packaging them into clathrin coated vesicles
- vesicle binds with late endosome
- acidic pH causes M6P to disassociate
- signal in the tail of M6P signals it to return to the golgi
- phosphate removed from mannose to ensure isn't transported back to golgi
- hydrolases digest macromolecues, endosome becomes lysosome
- signal peptide directs synthesis of lysosomal protein to the ER
- transport from lysosome
- passive diffusion
- membrane transporters
- digestion products transported out by transporters in the membrane
- endocytic pathway
- lysosomal secretion allows for break down of indigetable debris
- mainly when under stress
- defects can cause albiinism
- peroxisomes
- bags of oxidative enzymes
- sites of oxidative reactions
- beta-oxidation
- acetyl coenzyme a-exported to the cytoplasm for synthesis reactions and mitochondria for ATP production
- synthesis reactions
- e.g. first step in production of phosolipids in the myelin sheath
- protein import
- marked by c terminal signal
- proteins fully folded when imported
- use ATP
- Function
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