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Flashcards in Lysosomes Deck (14):

what is a lysosome?

an organelle of the endomembrane system that contains digestive enzymes capable of degrading all of the major classes of biological macromolecules


What does a lysosome look like?

0.5 um

single membrane - the lumenal side of membrane proteins is highly glycosylated which protects membrane proteins from lysosomal proteases



What type of environment is inside the lysosome - in terms of pH?

Acidic environment of 4.0-5.0

This favors enzymatic digestion of macromolecules both by activating acid hydrolases and by partially denaturing the macromolecules targeted for degradation


What types of acid hydrolases lie within the lysosome?

5 phosphatases, 14 proteases and peptidases, 2 nucleases,  6 lipases, 13 glycosidases and 7 sulfatases


Where do lysosomal enzymes come from?

synthesized by ribosomes, go from ER to Golgi for processing and packaging, from there they are endosomes and mature into lysosomes by the activation of acid hydrolases


what are heterophagic lysosomes?

lysosomes containing substances of extracellular origin (come from outside the cell)


What are autophagic lysosomes

lysosomes that contain materials of intracellular origin (from inside the cell)


How do the digested pieces of nucleic acids, proteins, carbohydrates etc, get across the membrane and into the cytosol?


some cross by faciliated diffusion while others need active transport to cross into the cytosol

the acidity of lysosomal lumen contributes  to an electochemical proton gradient across the lysosomal membrane


what is a residual body?

indigestable material in the lysosome that remains as digestion ceases


What is autophagy?

the digestion of old or unwanted organelles or other cell structures 


what is macrophagy?

a type of autophagy that begins when an organelle or other structure becomes wrapped in a double membrane derived from the ER


what is an autophagic vesicle?

a vesicle that resulted from macrophagy



What happens when there are lysosomal storage diseases?

skeletal deformaties, muscle weakness and mental retardation

Hurler syndrome and Hunter syndrome - both arise from defects in the degradation of glycosaminoglycans