Lysosome

A lysosome is a membrane-bound organelle in eukaryotic cells that contains digestive enzymes. It functions as the cell's "recycling center", breaking down excess or worn-out cell parts, macromolecules (proteins, carbohydrates, lipids, nucleic acids), and even invading pathogens.

• Lysosomes maintain an acidic internal pH (~5) optimal for their enzymes; if a lysosome leaks, the released enzymes are inactive in the neutral cytosol, protecting the cell.
• They play a key role in <u>autophagy</u> (digesting the cell's own broken organelles) and in defending against infection by digesting engulfed bacteria or viruses.
• Don't confuse lysosome (cellular organelle) with lysozyme (an enzyme in saliva and tears that breaks down bacterial cell walls) - a common exam trap!

• Often mentioned in questions about intracellular digestion - e.g., "Which organelle breaks down waste materials and worn-out organelles?" -> lysosome.
• Name trap -> *Lysosome* vs *Lysozyme*: Lysosomes are organelles; lysozyme is an enzyme (a classic trick to watch for).
• Organelle confusion -> Lysosomes vs peroxisomes: Lysosomes use acid hydrolase enzymes to digest materials, whereas peroxisomes carry out oxidative reactions (e.g., fatty acid breakdown and detoxification via hydrogen peroxide).