II. THE PROKARYOTIC CELL: BACTERIA

B. PROKARYOTIC CELL ANATOMY

3. Cellular Components Located Within the Cytoplasm

a. Cytoplasm

Fundamental Statements for this Learning Object:

1. In bacteria, the cytoplasm refers to anything enclosed by the cytoplasmic membrane.
2. The liquid portion of the cytoplasm is called the cytosol.
3. The cytoplasm is the site of most bacterial metabolism.
4. During catabolic reactions larger molecules are broken down to obtain cellular building block molecules and energy; during anabolic reactions cellular molecules and macromolecules are synthesized.

LEARNING OBJECTIVES FOR THIS SECTION

In this section on Prokaryotic Cell Anatomy we are looking at the various anatomical parts that make up a bacterium. As mentioned in the introduction to this section, a typical bacterium usually consists of:

• a cytoplasmic membrane surrounded by a peptidoglycan cell wall and maybe an outer membrane;
  
• a fluid cytoplasm containing a nuclear region (nucleoid) and numerous ribosomes; and
  
• often various external structures such as a glycocalyx, flagella, and pili.
  

We will now look at the bacterial cytoplasm.

The Cytoplasm (def)

A. Structure and Composition

In bacteria, the cytoplasm refers to everything enclosed by the cytoplasmic membrane. About 80% of the cytoplasm of bacteria is composed of water. Within the cytoplasm can be found nucleic acids (DNA and RNA), enzymes and amino acids, carbohydrates, lipids, inorganic ions, and many low molecular weight compounds. The liquid component of the cytoplasm is called the cytosol. Some groups of bacteria produce cytoplasmic inclusion bodies that carry out specialized cellular functions.

B. Functions

While bacteria secrete exoenzymes (def) to hydrolize macromolecules into smaller molecules capable of being transported across the cytoplasmic membrane, the cytoplasm is the site of most bacterial metabolism (def). This includes catabolic reactions in which molecules are broken down in order to obtain building block molecules for more complex cellular molecules and macromolecules, and anabolic reactions used to synthesize cellular molecules and macromolecules. The chemical reactions occuring within the bacterium are under the control of endoenzymes (def).

The various structurural filaments in the cytoplasm collectively make up the prokaryotic cytoskeleton. Prokaryotic cells possess analogs for all of the cytoskeletal proteins found in eukaryotic cells, as well as cytoskeletal proteins with no eukaryotic homologues. Cytoskeletal filaments play essential roles in determining the shape of a bacterium (coccus, bacillus, or spiral) and are also critical in the process of cell division by binary fission and in determining bacterial polarity.

 

• QUIZ YOURSELF ON THIS SECTION

Gary E. Kaiser, Ph.D.
Professor of Microbiology
The Community College of Baltimore County, Catonsville Campus
This work is licensed under a Creative Commons Attribution 4.0 International License.
Based on a work The Grapes of Staph at https://cwoer.ccbcmd.edu/science/microbiology/index_gos.html.

Last updated: August, 2018
Please send comments and inquiries to Dr. Gary Kaiser