STPM Biology Structure of Cell and Organelle (Part 8)

Lysosomes

Distribution:

• Lysosomes are distributed randomly in cytoplasm of animal cells.
• Lysosomes occur the most abundant in white blood cells, especially macrophages because these cell actively ingests and breaks down pathogens, dead cells and foreign particles.
• Lysosomes is not found in plant cells except for certain plants such as Nepenthes, Utricularia and Dionaea.

  

  Structure of Lysosome
  

Structure:

• Shape: Spherial or almost spherical.
• General size: 200nm – 500nm
• Lysosome is bounded by a membrane. This membrane is resistant to actions of digestive enzymes in the lysosome.
• Lysosome contains hydrolytic enzymes and proteins. Among the enzymes present are:
  • RNAase
  • DNAase
  • Lipase
  • Sulphatase
  • Protease
  • Hydrolase
  • Nuclease
  • Phophatase
  • Glucosidase
• Primary lysosome is a newly formed lysosome. when primary lysosome fuses with vacuoles, secondary lysosomes are formed.

Functions:

• Digestion of food in cells.
• Carries out autophagy, the breaking down of old, worn organelles.
• Conducts cell autolysis, that is the automatic breakdown of old or worn cells.
• Involved in shrinking of tadpole’s tail during metamorphosis.
• Involved in destruction pathogens.
• Play and important role in insect metamorphosis. Enzymes of lysosomes break down the larvae/nymph tissues during metamorphosis.

  

  Function of Lysosome