Food Vacuole

Food Vacuole Definition

“Food vacuole” is one of the more complicated terms to research – because there are two different definitions of this term in common use!

Some scientists refer to a “food vacuole” as any large sac inside a cell that contains food for the cell; vacuoles are used to store cellular fuel by some cells in animals, plants, fungi, and microorganisms.

Others define “food vacuole” as being a specific type of digestive vacuole which is only found in certain protozoan microorganisms.

Be certain you know which type your labmates or teachers are referring to when they talk about food vacuoles – otherwise, you may end up very confused!

Here, we will discuss the more technical definition – vacuoles that are used by some protozoans to digest food.

Function of Food Vacuole

Food vacuoles are membrane-bound sacs within a cell, which contain food matter to be digested. These can be thought of as intracellular “stomachs,” where food is stored while it is broken down and its nutrients are extracted.

To begin the cellular “eating” process, the cell membrane curves to envelope a particle of food. When the cell membrane has enveloped the food completely, it “pinches off,” moving the food fully inside the cell.

The membrane surrounding the food particle is now a “vacuole” – a large membrane-bound sac within the cell.

Phagocytosis

Phagocytosis (click to play animated GIF)

The process of the cell ingesting food by wrapping its membrane around it is called “phagocytosis.” That term derives from the root words “phage” for “eat” and “cyto” for “cell.” So “phagocytosis” means, literally, “cell eating.”

Once the food vacuole has been created inside the cell, the cell begins to digest it, using a lysosome.

Lysosomes are special membrane-bound sacs inside of cells that contain the cellular equivalent of stomach acid. Just like our stomachs, they contain acid and enzymes to break down nutrients into usable forms.

When a cell wants to digest the food inside a vacuole, the vacuole merges with lysosomes. As the two membrane-bound sacs merge, the contents of the lysosome spill into the food vacuole – and begin digesting the food within.

Over time, the food is converted into usable nutrients for the cell such as sugars, amino acids, and lipids.

Any materials that aren’t usable to the cell are eventually expelled when the vacuole merges again with the cell membrane.

Quiz

1. Why are there two definitions of “food vacuole?”
A. Because organisms use vacuoles for many different purposes.
B. Because many organisms store food in vacuoles, but there are some differences in how these vacuoles function.
C. Because “food” and “vacuole” are both commonly used terms in biology.
D. None of the above.

Answer to Question #1
B is correct. People use the term “food vacuole” in different ways because many organisms store food in vacuoles.

However, the term was first applied to the process of digestion used by protozoans, and that is still the dictionary definition of this term.

Answers A. and C. are also true, but B. is the most specific answer to this question.

References

  • Food vacuole. (n.d.). Retrieved April 23, 2017, from http://www.dictionary.com/browse/food vacuole
  • Protozoa. (n.d.). Retrieved April 23, 2017, from http://www.biologyreference.com/PoRe/Protozoa.html
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