Lysosomes
Cell biology
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• Lysosomes are spherical organelles that
contain enzymes (acid hydrolases). They break
up food so it is easier to digest. They are found
in animal cells, while in yeast and plants the
same roles are performed by lytic vacuoles.
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• The size of lysosomes varies from 0.1–1.2 μm.
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• Lysosomes are common in animal cells but
rare in plant cells contain hydrolytic enzymes
necessary for intracellular digestion.
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• Some important enzymes found within
lysosomes include:
• Lipase, which digests lipids
• Amylase, which digest carbohydrates (e.g.,
sugars)
• Proteases, which digest proteins
• Nucleases, which digest nucleic acids
• phosphoric acid monoesters.
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• All these hydrolytic enzymes are produced in
the endoplasmic reticulum, and to some
extent in cytoplasm are transported and
processed through the Golgi apparatus.
• and through golgi apparatus they pinch off as
single membrane vesicles.
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• It is called
• "The Police Force of the Cell"
• "suicide bags“
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• Lysosomes are produced in the Golgi
Apparatus
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• Lysosomes are sometimes called "suicide
bags“
• A lysosome is a membrane bag containing
digestive enzymes
• to digest food, the lysosome membrane fuses
with the membrane of a food vacuole and
squirts the enzymes inside.
• The digested food can then diffuse through
the vacuole membrane and enter the cell to
be used for energy or growth.
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• Lysosomes are the cells' garbage disposal
system. They are used for the digestion of
macromolecules from phagocytosis (ingestion
of other dying cells or larger extracellular
material, like foreign invading microbes) .
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• endocytosis (where receptor proteins are
recycled from the cell surface), and autophagy
(wherein old or unneeded organelles or
proteins, or microbes that have invaded the
cytoplasm are delivered to the lysosome).
Autophagy may also lead to autophagic cell
death, a form of programmed self-destruction,
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• Autophagy may also lead to autophagic cell
death, a form of programmed self-destruction,
or autolysis, of the cell, which means that the
cell is digesting itself.
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• Lysosomes pick up foreign invaders such as
bacteria, food and old organelles and break
them into small pieces that can hopefully be
used again.
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• Lysosomal enzymes are synthesized in the cytosol
and the endoplasmic reticulum, where they receive
a mannose-6-phosphate tag that targets them for
the lysosome.
• If the lysosomal enzymes do not reach the target it
causes inclusion-cell disease, resulting in
accumulation of waste within these organelles.
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• The only thing that keeps the cell itself from
being digested is the membrane surrounding
the lysosomes.
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• These enzymes work only at low pH (highly
acidic) levels.
• However because they can only work at low
pH levels and the rest of the cell has a neutral
pH level, they can be neutralized if they
accidentally escape from the lysosome
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• In white blood cells that eat bacteria,
lysosome contents are carefully released into
the vacuole around the bacteria and serve to
kill and digest those bacteria. Uncontrolled
release of lysosome contents into the
cytoplasm can also cause cell death (necrosis).
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