Among the many important membrane-bound organelles in the cell is the sac-like Lysosome. Its basic function is digestion. A cell ingests food or any other material into it, and stores it in a vesicle-like structure called an endosome. We do not pretty much know how this ingested substance reaches the lysosome from the endosome. However, a rough guess is that either the endosome fuses with the Lysosome, or matures and develops into it.
Lysosomes contain about 40 different types of hydrolytic enzymes, including those that degrade proteins, nucleic acids, oligosaccharides, and phospholipids. All of these enzymes are optimally active in the acidic conditions (pH~5) maintained within Lysosomes, against the basic cytosol outside. The Lysosome not only contains a unique collection of enzymes but also has a unique surrounding membrane.
The Lysosomal membrane is very special indeed. It contains transport proteins that allow the final products of the digestion of macromolecules to be transported to the cytosol, from where they can be either excreted or utilised by the cell. It also contains an ATP-driven H+ pump which pumps H+ (protons) into the lysosome, thereby maintaining its contents at an acidic pH. Most of the Lysosomal membrane proteins are unusually highly glycosylated: the sugars, which cover much of the protein surfaces facing the lumen, protect the proteins from digestion by the Lysosomal proteases.
A Lysosome may digest one of the cell’s own organelles, or even the cell itself (by rupturing the Lysosomal wall and letting the acids within to flow out)- this it does when destruction becomes necessary to protect the other cells nearby from acquiring same infection that its own cell has caught. Hence, Lysosomes are often referred to as the ‘suicide bags’ of the cell.
Lysosomes contain about 40 different types of hydrolytic enzymes, including those that degrade proteins, nucleic acids, oligosaccharides, and phospholipids. All of these enzymes are optimally active in the acidic conditions (pH~5) maintained within Lysosomes, against the basic cytosol outside. The Lysosome not only contains a unique collection of enzymes but also has a unique surrounding membrane.
The Lysosomal membrane is very special indeed. It contains transport proteins that allow the final products of the digestion of macromolecules to be transported to the cytosol, from where they can be either excreted or utilised by the cell. It also contains an ATP-driven H+ pump which pumps H+ (protons) into the lysosome, thereby maintaining its contents at an acidic pH. Most of the Lysosomal membrane proteins are unusually highly glycosylated: the sugars, which cover much of the protein surfaces facing the lumen, protect the proteins from digestion by the Lysosomal proteases.
A Lysosome may digest one of the cell’s own organelles, or even the cell itself (by rupturing the Lysosomal wall and letting the acids within to flow out)- this it does when destruction becomes necessary to protect the other cells nearby from acquiring same infection that its own cell has caught. Hence, Lysosomes are often referred to as the ‘suicide bags’ of the cell.
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