<P> In plant cells, vacuoles cover anywhere from 30% to 90% of the total cell volume . 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 ions surging into the cytosol can be transferred to a vacuole in order to keep the cytosol's pH constant . </P> <P> 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 . </P> <P> Vesicles are small membrane - enclosed transport units that can transfer molecules between different compartments . Most vesicles transfer the membranes assembled in the endoplasmic reticulum to the Golgi apparatus, and then from the Golgi apparatus to various locations . </P> <P> There are various types of vesicles each with a different protein configuration . Most are formed from specific regions of membranes . When a vesicle buds off from a membrane it contains specific proteins on its cytosolic surface . Each membrane a vesicle travels to contains a marker on its cytosolic surface . This marker corresponds with the proteins on the vesicle traveling to the membrane . Once the vesicle finds the membrane, they fuse . </P>

Name the three main components of a eukaryotic cell