Lysosome

Lysosome

A lysosome is a membrane-bound organelle found in most animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, both as to its membrane proteins, and its lumenal proteins.

Structure

The lysosome is surrounded by a membrane that maintains an acidic environment within the interior via a proton pump. This membrane protects the cytosol, and therefore the rest of the cell, from the degradative enzymes within the lysosome. The lysosomal membrane also contains proteins necessary for fusion with other organelles and transport of materials into and out of the cell.

Function

Lysosomes act as the waste disposal system of the cell by digesting unwanted materials in the cytoplasm, both from outside of the cell and from within the cell. They are responsible for the breakdown and recycling of cellular waste products, cellular signalling and energy metabolism. The enzymes within lysosomes are responsible for breaking down waste materials and cellular debris.

Clinical significance

Defects in lysosomal enzyme synthesis can lead to a variety of diseases, collectively known as lysosomal storage diseases. These diseases result from an accumulation of specific substrates, due to the inability to break them down. These diseases are most commonly caused by the malfunction of a single enzyme.

See also

• Autophagy
• Endocytosis
• Exocytosis
• Phagocytosis
• Proteolysis

References

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  Diagram of lysosome digestion
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  Lysosome in biological context
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  Endocytic pathway involving lysosomes