Tutoring biology, the cell is fundamental. Heading towards another weekend Biology 12 workshop, the biology tutor recalls Bruce Willis’s advice in Last Boy Scout: “Be prepared.”
A cell, like anyone, needs storage. More than that, it needs storage for different purposes. While you keep your food in the pantry, you store your clothes in the bedroom closet. The cell faces similar storage challenges.
The three main types of storage vessels a cell uses are vesicles, vacuoles, and lysosomes. Each has its own particular use and features:
Vesicles are often used for transport. For example, they are used to store molecules or food arriving from outside the cell. Vesicles are also used to hold partially completed molecules the cell is making as they are moved to different “work sites”. Then, when a molecule is to be secreted from the cell, it is shipped to the outer membrane in a vesicle, then released outside.
A vacuole is larger than a vesicle. Vacuoles are meant for storage until use – or even permanent storage. Water, sugars, and even pigments are stored in vacuoles. In the case of pigment, it will remain in the vacuole for the life of the cell, giving the cell color. A water vacuole holds a large amount of water in order to “fill out” the cell, giving it the proper shape. Plants derive their rigid shape partially from the water in their cells’ vacuoles. Vacuoles can also hold toxic by-products until the cell gets around to destroying them. Although both plant and animal cells contain vacuoles, plants use them more.
A lysosome is a special type of vesicle that stores digestive enzymes (see my previous post). A vesicle containing food will be fused with a lysosome for digestion to take place.
A cell can be a busy place. Any such place needs ample storage. Fortunately for the cell, it can make new vesicles, vacuoles, or lysosomes as needed:)
Source: Inquiry into Life, 11th Edition. Mader, Sylvia. New York: McGraw-Hill, 2006.
Jack or Oracle Tutoring by Jack and Diane, Campbell River, BC.