Cell Biology/Lysosomes

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<< Golgi apparatus | Lysosomes | Peroxisomes >>

Lysosomes
Membrane-bound sacs called lysosomes contain digestive enzymes that can break down such macromolecules as proteins, nucleic acids, and polysaccharides (Figure 6-23). Lysosomes have several functions. They fuse with incoming food vacuoles and expose the nutrients to enzymes that digest them, thereby nourishing the cell. Lysosomes also function like safety officers when they help destroy harmful bacteria. In certain cells—for example, your white blood cells—lysosomes release enzymes into vacuoles that contain trapped bacteria and break down the bacterial cell walls. Similarly, lysosomes serve as recycling centers for damaged organelles. Without harming the cell, a lysosome can engulf and digest another organelle. This makes molecules available for the construction of new organelles.The structures vary in size from 0.2 to 2 micrometers in diameter. The staining reveals a crystal like matrix in spherical vesicles. The crystalloid matrix is urate oxidase. These are small organelles containing around 40 enzymes for intercellular digestion. The lysosome membrane helps to protect the enzymes as much as it helps protect the cell. This is because the optimal pH for these enzymes is around a pH of 5. The membrane of the lysosome is again a lipid bilayer and is thought to have a ATP hydrolysis to pump H+ into the lysosome to maintain the pH. This also has another affect, that is free protons. Other small molecules can pass through the lysosome membrane, but will then become charged by picking up a free proton, then they are less likely to be able to leave the lysososome. A good reference on Lysosomes is at
 * http://cellbio.utmb.edu/cellbio/lysosome.htm

<< Golgi apparatus | Lysosomes | Peroxisomes >>

Cell Biology | Parts of the cell Organelles