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Lysosomes are organelles in eukaryotic cells that contain digestive enzymes to digest macromolecules. They are built in the Golgi apparatus. At pH 4.8, the interior of the lysosomes is more acidic than the cytosol (pH 7). The lysosome single membrane stabilizes the low pH by pumping in protons (H+) from the cytosol, and also protects the cytosol, and therefore the rest of the cell, from the degradative enzyme s within the lysosome. The digestive enzymes need the acidic environment of the lysosome to function correctly. All these enzymes are produced in the endoplasmic reticulum, and transported and processed through the Golgi apparatus. The Golgi apparatus produces lysosomes by budding. The most important enzymes in lysosomes are:
- Lipase, which digests lipids,
- Carbohydrase s, which digest carbohydrates (e.g., sugars),
- Proteases, which digest proteinmyoglobin, showing coloured alpha helices. This protein was the first to have its structure solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, which led to them receiving a Nobel Prize in Chemistry. A protein is a complex,s,
- NucleaseA nuclease is an enzyme capable of cleaving the phosphodiester bonds between the nucleotide subunits of nucleic acids. Introduction In the late 1960's, scientists Stewart Linn and Werner Arber isolated examples of the two types of enzymes responsible fors, which digest nucleic acidA nucleic acid is a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information. The most common nucleic acids are deoxyribonucleic acid ( DNA) and ribonucleic acid ( RNA). Nucleic acids are founds.
The lysosomes are used for the digestion of macromolecules from phagocytosisIn phagocytosis (literally, "cell eating"), large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a food vacuole. In animals, phagocytosis is performed by specialized phagocytotic cells or phagocytes, which (ingestion of food), from the cell's own recycling process (where old components such as worn out mitochondria are continuously destroyed and replaced by new ones, and receptor proteins are recycled), and for autophagic cell deathAutophagy or autophagocytosis is a process of organelle degradation that takes place inside the cell. It is executed by lysosomes and is part of everyday normal cell growth and development. Its main purpose is to maintain a balance between biogenesis (pro, a form of programmed self-destructionProgrammed cell death PCD is the deliberate suicide of an unwanted cell in a multicellular organism. In contrast to necrosis, which is a form of cell death that results from acute tissue injury and provokes an inflammatory response, PCD is carried out in of the cell, which means that the cell is digesting itself.
Other functions include digesting foreign bacteria that invade a cell and helping repair damage to the plasma membrane by serving as a membrane patch, sealing the wound.
There are a number of illnesses that are caused by the malfunction of the lysosomes or one of their digestive proteins, e.g., Tay-Sachs disease, or Pompe's disease. These are caused by a defective or missing digestive protein, which leads to the accumulation of substrates within the cell, resulting in impaired cell metabolism. Broadly, these can be classified as mucopolysaccharidoses, GM2 gangliosidoses , lipid storage disorder s, glycoproteinoses , mucolipidoses , or leukodystrophies .
The constant pH of 4.8 is maintained by hydrogen ion pumps and Cl- ion channels.
This article or image contains material from the Science Primer published by the NCBI, which, as a US government publication, is in the public domain [1].
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