Cell Biology: Functions of Lysosomes

Lysosomes

• Lysosomes are membrane-bound organelles that digest various molecules and substances within a cell.
• The root "lys" means "to cut or digest".
• Lysosomes have two main functions: Autophagy and Crinophagy.

Autophagy

• Autophagy means "self-eating" and involves the digestion of molecules that are part of the cell itself or other cells.
• Examples of autophagy include:
  • Breaking down non-functional organelles, such as old mitochondria.
  • Digesting engulfed bacteria and viruses in macrophages of the immune system.

Crinophagy

• Crinophagy involves the digestion of excess secretory products.
• Example: Breaking down excess hormones produced by a cell.
• In both Autophagy and Crinophagy, the lysosomes release the broken-down molecules into the cytoplasm as building blocks, which can be reused by the cell.

Environment in Lysosomes

• The enzymes in lysosomes, known as acid hydrolases, require an acidic environment to work properly.
• The pH inside a lysosome is approximately 5, which acts as a safety mechanism for the cell.
• If a lysosome were to burst, the acid hydrolases would not function properly in the cytoplasm due to its higher pH (approximately 7.4).

Peroxisomes

• Peroxisomes are membrane-bound organelles responsible for various metabolic activities.
• They are similar to lysosomes but have different functions.
• Examples of peroxisome functions include:
  • Lipid break down in some cells.
  • Detoxifying chemicals and drugs in liver cells.
• Peroxisomes contain enzymes, including catalase, which breaks down hydrogen peroxide into water and oxygen.
• Hydrogen peroxide is a by-product of certain enzyme activities and is dangerous to the cell if not isolated and broken down.

Learn about the roles of lysosomes in cellular digestion, including autophagy and crinophagy. Understand how they break down molecules and substances within cells.