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Subject - cell biology

Lysosomes are organelles bound by a single membrane, which play an important role in the degradation of substances taken up by the cell. They contain numerous lysosomal enzymes, including proteases, nucleases (German learning unit), lipases, and phosphatases, whose optimal pH values are adapted to the acidic pH values between about 4.5 and 5 found within the lysosomes. Lysosomes are formed in a manner similar to secretory vesicles in the endoplasmic reticulum and are separated off in the distal compartment of the Golgi apparatus.

These primary lysosomes fuse with endocytic vesicles. This fusion produces secondary lysosomes in which the hydrolytic breakdown of diverse molecules taken up from the exterior through endocytosis occurs. Some intracellular parasites like Plasmodium (cause of malaria) are taken into the cell by endocytosis but can prevent fusion with a primary lysosome, which allows them to survive.

Recessively inherited lysosomal storage diseases are known. They are caused by disruption of lysosomal enzyme function, which prevents certain substances from being broken down; instead, they accumulate in vacuoles in the cytoplasm.

Recommended Learning Units

Cell Structure and Cell OrganellesLevel 160 min.

BiochemistryBiological FundamentalsCell Morphology

Cytology is introduced by means of illustrations, animations, and a comprehensive collection of references and selected links.