Editing Endomembrane system (section)

=== Vacuoles ===
{{main|Vacuole}}

[[Vacuole]]s, like vesicles, are membrane-bound sacs within the cell. They are larger than vesicles and their specific function varies. The operations of vacuoles are different for plant and animal vacuoles.

In plant cells, vacuoles cover anywhere from 30% to 90% of the total cell volume.<ref name=Alberts5>{{cite web|url=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=Vacuoles&rid=mboc4.section.2363#2369|title=Plant and Fungal Vacuoles Are Remarkably Versatile Lysosomes|access-date=2008-12-09|last=Alberts|first=Walter| name-list-style = vanc |year=2002|work= Molecular Biology of the Cell 4th edition|publisher=Garland Science|display-authors=etal}}</ref> Most mature plant cells contain one large central vacuole encompassed by a membrane called the tonoplast. Vacuoles of plant cells act as storage compartments for the nutrients and waste of a cell. The solution that these molecules are stored in is called the [[cell sap]]. [[Pigments]] that color the cell are sometime located in the cell sap. Vacuoles can also increase the size of the cell, which elongates as water is added, and they control the [[turgor pressure]] (the osmotic pressure that keeps the cell wall from caving in). Like lysosomes of animal cells, vacuoles have an acidic pH and contain hydrolytic enzymes. The pH of vacuoles enables them to perform homeostatic procedures in the cell. For example, when the pH in the cells environment drops, the H<sup>+</sup> ions surging into the cytosol can be transferred to a vacuole in order to keep the cytosol's pH constant.<ref name=Lodish1>{{cite web|url=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=Vacuoles&rid=mcb.section.1182#1187|title=Plant Vacuoles Store Small Molecules and Enable the Cell to Elongate Rapidly|access-date=2008-12-09|last=Lodish|first=Harvey| name-list-style = vanc |year=2000|work= Molecular Cell Biology|publisher=W. H. Freeman and Company|display-authors=etal}}</ref>

In animals, vacuoles serve in [[exocytosis]] and [[endocytosis]] processes. Endocytosis refers to when substances are taken into the cell, whereas for exocytosis substances are moved from the cell into the extracellular space. Material to be taken-in is surrounded by the plasma membrane, and then transferred to a vacuole. There are two types of endocytosis, [[phagocytosis]] (cell eating) and [[pinocytosis]] (cell drinking). In phagocytosis, cells engulf large particles such as bacteria. Pinocytosis is the same process, except the substances being ingested are in the fluid form.<ref name=Cooper5>{{cite web|url=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=phagocytosis&rid=cooper.section.2017#2018|title=Endocytosis|access-date=2008-12-09|last=Cooper|first=Geoffrey| name-list-style = vanc |year=2000|work= The Cell: A Molecular Approach|publisher=Sinauer Associates, Inc}}</ref>