Lysosome

lysosomallysosomeslysosomal enzymesendolysosomelysozomeendolysosomal systemlysosomal activitylysosomal enzymenon-lysosomalysosomal
A lysosome is a membrane-bound organelle found in many animal cells and most plant cells.wikipedia
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Vesicle (biology and chemistry)

vesiclesvesiclevesicular
They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules.
Alternatively, they may be prepared artificially, in which case they are called liposomes (not to be confused with lysosomes).

Christian de Duve

De DuveDe Duve, ChristianDe Duve, Christian Rene
They were discovered and named by Belgian biologist Christian de Duve, who eventually received the Nobel Prize in Physiology or Medicine in 1974.
He made serendipitous discoveries of two cell organelles, peroxisome and lysosome, for which he shared the Nobel Prize in Physiology or Medicine in 1974 with Albert Claude and George E. Palade ("for their discoveries concerning the structural and functional organization of the cell").

Autophagy

macroautophagyautophagicautophagic pathway
Material from outside the cell is taken-up through endocytosis, while material from the inside of the cell is digested through autophagy. In addition to being able to break down polymers, lysosomes are capable of fusing with other organelles & digesting large structures or cellular debris; through cooperation with phagosomes, they are able to conduct autophagy, clearing out damaged structures.
The autophagosome eventually fuses with lysosomes and the contents are degraded and recycled.

Lumen (anatomy)

lumenluminallumina
A lysosome has a specific composition, of both its membrane proteins, and its lumenal proteins.
*thylakoid, endoplasmic reticulum, Golgi apparatus, lysosome, mitochondrion, or microtubule

Cell (biology)

cellcellscellular
A lysosome is a membrane-bound organelle found in many animal cells and most plant cells.
Some (such as the nucleus and golgi apparatus) are typically solitary, while others (such as mitochondria, chloroplasts, peroxisomes and lysosomes) can be numerous (hundreds to thousands).

Mannose 6-phosphate

mannose-6-phosphate
Enzymes destined for a lysosome are specifically tagged with the molecule mannose 6-phosphate, so that they are properly sorted into acidified vesicles.
M6P is a key targeting signal for acid hydrolase precursor proteins that are destined for transport to lysosomes.

Liposome

liposomesliposomallipid shell
Lysosomes should not be confused with liposomes, or with micelles.
Liposomes should not be confused with lysosomes, or with micelles and reverse micelles composed of monolayers.

Golgi apparatus

Golgitrans-Golgi networkGolgi bodies
The enzymes are imported from the Golgi apparatus in small vesicles, which fuse with larger acidic vesicles.
The CGN is the first cisternal structure, and the TGN is the final, from which proteins are packaged into vesicles destined to lysosomes, secretory vesicles, or the cell surface.

Acid phosphatase

acid phosphatases
To estimate this enzyme activity, they used that of standardised enzyme acid phosphatase, and found that the activity was only 10% of the expected value.
Acid phosphatase is stored in lysosomes and functions when these fuse with endosomes, which are acidified while they function; therefore, it has an acid pH optimum.

Organelle

organellescell organellescell organelle
A lysosome is a membrane-bound organelle found in many animal cells and most plant cells.

Phagosome

phagosomesphagocytic vacuolephagosomal
In addition to being able to break down polymers, lysosomes are capable of fusing with other organelles & digesting large structures or cellular debris; through cooperation with phagosomes, they are able to conduct autophagy, clearing out damaged structures.
Phagosomes have membrane-bound proteins to recruit and fuse with lysosomes to form mature phagolysosomes.

Endocytosis

endocytosedendocyticinternalization
Material from outside the cell is taken-up through endocytosis, while material from the inside of the cell is digested through autophagy. For instance, in endocytosis (more specifically, macropinocytosis), a portion of the cell's plasma membrane pinches off to form vesicles that will eventually fuse with an organelle within the cell.
Pinocytosis, which usually occurs from highly ruffled regions of the plasma membrane, is the invagination of the cell membrane to form a pocket, which then pinches off into the cell to form a vesicle (.5–5 µm in diameter) filled with a large volume of extracellular fluid and molecules within it (equivalent to ~100 CCVs). The filling of the pocket occurs in a non-specific manner. The vesicle then travels into the cytosol and fuses with other vesicles such as endosomes and lysosomes.

Enzyme

enzymologyenzymesenzymatic
They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules.
In addition, trafficking of the enzyme to different compartments may change the degree of protonation (e.g., the neutral cytoplasm and the acidic lysosome) or oxidative state (e.g., oxidizing periplasm or reducing cytoplasm) which in turn affects enzyme activity.

Phagocytosis

phagocyticphagocytosedphagocytose
Similarly, they are able to break-down virus particles or bacteria in phagocytosis of macrophages.
For example, when a macrophage ingests a pathogenic microorganism, the pathogen becomes trapped in a phagosome which then fuses with a lysosome to form a phagolysosome.

Cathepsin

cathepsinscathepsin bcathepsin d
It sources its versatile capacity for degradation by import of enzymes with specificity for different substrates; cathepsins are the major class of hydrolytic enzymes, while lysosomal alpha-glucosidase is responsible for carbohydrates, and lysosomal acid phosphatase is necessary to release phosphate groups of phospholipids.
Most of the members become activated at the low pH found in lysosomes.

V-ATPase

V-type proton ATPasevacuolar proton-translocating atpasesVacuolar-ATPase
Vacuolar-ATPases are responsible for transport of protons, while the counter transport of chloride ions is performed by ClC-7 Cl − /H + antiporter.
V-ATPases are found within the membranes of many organelles, such as endosomes, lysosomes, and secretory vesicles, where they play a variety of roles crucial for the function of these organelles.

Cytoplasm

cytoplasmiccytosolicintracytoplasmic
The lysosomes also act as the waste disposal system of the cell by digesting unwanted materials in the cytoplasm, both from outside the cell and obsolete components inside the cell.
Some major organelles that are suspended in the cytosol are the mitochondria, the endoplasmic reticulum, the Golgi apparatus, vacuoles, lysosomes, and in plant cells, chloroplasts.

Alex B. Novikoff

Novikoff
The same year, Alex B. Novikoff from the University of Vermont visited de Duve's laboratory, and successfully obtained the first electron micrographs of the new organelle.
In 1955, now confident that the membranous particles were cell organelles, de Duve gave a hypothetical name "lysosomes" to reflect their digestive properties.

Mannose 6-phosphate receptor

M6PRmannose-6-phosphate pathwaymannose-6-phosphate receptor
The presence of these tags allow for binding to mannose 6-phosphate receptors in the Golgi apparatus, a phenomenon that is crucial for proper packaging into vesicles destined for the lysosomal system.
The mannose 6-phosphate receptors (MPRs) are transmembrane glycoproteins that target enzymes to lysosomes in vertebrates.

Lysosomal storage disease

lysosomal storage diseaseslysosomal storage disorderlysosomal storage disorders
Mutations in the genes for these enzymes are responsible for more than 30 different human genetic disorders, which are collectively known as lysosomal storage diseases.
Lysosomes are sacs of enzymes within cells that digest large molecules and pass the fragments on to other parts of the cell for recycling.

Cell death

diedeathcell killing
However, it has since been concluded that they only play a minor role in cell death.
Macroautophagy, often referred to as autophagy, is a catabolic process that results in the autophagosomic-lysosomal degradation of bulk cytoplasmic contents, abnormal protein aggregates, and excess or damaged organelles.

Macrophage

macrophagesTissue macrophagesCD68 + macrophages
Similarly, they are able to break-down virus particles or bacteria in phagocytosis of macrophages.
When a macrophage ingests a pathogen, the pathogen becomes trapped in a phagosome, which then fuses with a lysosome.

Pinocytosis

macropinocytosispinocytoticpinocytotic vesicles
For instance, in endocytosis (more specifically, macropinocytosis), a portion of the cell's plasma membrane pinches off to form vesicles that will eventually fuse with an organelle within the cell.
These pinocytotic vesicles subsequently fuse with lysosomes to hydrolyze (break down) the particles.

Lysosomal lipase

lysosomal acid lipase
Lysosomes contain a variety of enzymes, enabling the cell to break down various biomolecules it engulfs, including peptides, nucleic acids, carbohydrates, and lipids (lysosomal lipase).
Lysosomal lipase is a form of lipase which functions intracellularly, in the lysosomes.

Acid alpha-glucosidase

acid maltasealpha-1,4-glucosidaseGAA
It sources its versatile capacity for degradation by import of enzymes with specificity for different substrates; cathepsins are the major class of hydrolytic enzymes, while lysosomal alpha-glucosidase is responsible for carbohydrates, and lysosomal acid phosphatase is necessary to release phosphate groups of phospholipids.
Acid alpha-glucosidase, also called α-1,4-glucosidase and acid maltase, is an enzyme that helps to break down glycogen in the lysosome.