Do Prokaryotes Cells have Cytoplasm? 6 Facts You Should Know


In this article, we illustrate about the fact that do prokaryotic cells have cytoplasm by explaining different aspects of cytoplasm.

Most of the prokaryotic cells are small, single celled, free living. Prokaryotic cells are enclosed in the plasma membrane. There is no membrane bound cell organelle present in the cytoplasm.

In the cytoplasm of prokaryotic cells, various cell organelles like ribosome, nucleoid (bacterial genetic material) and plasmid (circular DNA different from chromosomal DNA)

Do all prokaryotic cells have cytoplasm?

All the prokaryotic cells either Bacteria or Archaea have cytoplasm inside its plasma membrane. The cytoplasm of prokaryotes defines everything which found inside the cytoplasm. The main component of cytoplasm is cytosol (water based solution having ions, small molecules and macromolecules).

The cytoplasm is the integral part of both eukaryotic and prokaryotic cells. Its function to maintain the optimal environmental for the cellular organelles. Cytosol of cytoplasm has many functions, some of them are signal transduction, metabolites and molecules transportation across the cell, structural support to the cell.

When the prokaryotic cytoplasm observed under simple microscope, it appears transparent. But the bacterial cytoplasm by transmission electron microscope, it looked like granular liquid. The majority composition of cytoplasm is water.

The bacteria cytoplasm consistency more liquidity as compare to the eukaryotic cytoplasm. The liquidly consistency in cytoplasm of bacteria is vital, since the molecules which present inside the cytoplasm should be able to move within bacteria as well as into and out of the cytoplasm

do prokaryotic cells have cytoplasm
Bacterial cell from Wikipedia

Where do prokaryotic cells have cytoplasm?

Prokaryotic cells having cytoplasm inside the membrane that enclosed the bacteria. As the prokaryotic bacteria do not have nucleus thus which is present inside the plasma membrane called as cytoplasm.

In bacterial cytoplasm, there is complete chemical and biochemical machinery is present. All kind of metabolic activities like replication, transcription and translation occur in the cytoplasm. All kind of enzymes need to carry out above process are also present inside the cytoplasm. While few chemical reactions take place in membrane or in the periplasmic space (the space between outer cell wall and inner plasm membrane).

The main composition of prokaryotic cells has cytosol, cytoplasmic inclusion bodies and various other cell organelle. The cytoplasm is about 80% watery in nature. The cytosol also known as cytoplasmic matrix or groundplasm. Cytosol is liquid found inside the cell as intracellular fluid. The presence of ions in the cytosol maintain the concentration gradient of cell.

Do prokaryotic cells have cytoplasmic membrane?

All the prokaryotic and eukaryotic cells have cytoplasmic membrane. The cytoplasmic membrane is defined as the membrane that surrounded the cytoplasm of the cells. The cytoplasmic membrane also known as cell membrane or plasma membrane.

The plasm membrane is made of lipid bilayer (two layer of phospholipids) with membrane proteins are interspersed between the lipid layer to maintain the fluidity of membrane. The bacterial cytoplasmic layer act as permeability barrier to most molecules. Bacterial membrane does not have sterols as in eukaryotes except present in Mycoplasma and methanotrophs. To carry out the function of sterols, many bacteria contain hopanoids.

The cytoplasmic membrane also protect cell from the external environments. It provides the shape to the cells. The cytoplasmic membrane of prokaryotic cells has more fatty acid as compare to eukaryotic cells. The fatty acids act as barrier to most the molecules and also help to maintain the fluidity of cell.

Do prokaryotic cells have liquid cytoplasm?

Cytoplasm or protoplasm of a prokaryotic cells is a jelly or gel like matrix composed of around 80% water, enzymes, wastes, nutrients, gases, low molecular weight molecules, inorganic ions and cell organelles like ribosome, chromosome (nucleoid) and plasmids.

When all the cell organelles excluded then the cytoplasmic matrix left is known as groundplasm. The concentrated inner area around center is called endoplasm and outer layer is called cell cortex or ectoplasm.

The cytosol of the cytoplasm is the gel like portion which do not contained within membrane bound organelles. It formed around 70-80% of total cytoplasm having mixture of cytoskeleton filaments, dissolved molecules and water. Due to watery composition of cytoplasm, it appears transparent when we observed under microscope.

Do prokaryotic cells have DNA in cytoplasm?

In many prokaryotic cells, the DNA is present as a genetic material. In most of cases in bacteria, it is circular single chromosome but, in some bacteria (Vibrio cholera), may have two chromosomes. Also, in some cases of bacteria, DNA may be liner rather than circular.

The chromosomal DNA responsible to carry out the genetic information from its parent to its next generation. While in the prokaryotic cells, there is also plasmid DNA present which is also called extrachromosomal DNA.

Most of plasmid DNA are supercoiled, circular double-stranded DNA molecules. Plasmid DNA usually encodes such traits which are not important to viability of the bacterial cells. Many plasmid control important properties of bacteria mainly resistance to antibiotics, toxin production and synthesis of cell structure that are require for cell adherence or colonization.

Prokaryotic cells lack well organized nucleus. The DNA of prokaryotic cells found at the center of the cells called nucleoid. The length of single chromosomes is very long that condensed to fit in a tiny cell.

Most of prokaryotic cells do not use histones for DNA storage just like in eukaryotic cells. Prokaryotic DNA undergo supercoiling that helps for the application o tension to twist the DNA molecules, so it can wrap around itself and create the loops. Instead of histones, the prokaryotic DNA have nucleoid-associated proteins (NAPs) for folding. NAPs are the proteins which binds to DNA molecules, introducing folds and bends and later they also participate in the DNA replication and transcription.

Most prokaryotic cells have just one chromosome so they are called haploid in nature (1n, absence of paired chromosome). Even in the case of Vibrio cholerae, having two chromosomes, the chromosomes are differing from each other. The chromosomes are non-homologous pair because they do not have same gene on both the chromosomal DNA.

Do prokaryotic cells have plasmid DNA in cytoplasm?

The plasmid is small, circular , ds DNA (double stranded DNA) that differ from chromosomal DNA of cell. in the prokaryotic cells, plasmids are present naturally. Plasmid also exists in some eukaryotic cells.

Plasmids having DNA carry genes which are beneficial to bacteria like antibiotic resistance, marker genes etc. plasmid DNA is small as compare to the chromosomal DNA. It replicates by its own without any help of chromosomal replication machinery. There are many artificial and synthetic plasmids are used in laboratory for the process of molecular cloning, mostly used as vector for replication of recombinant DNA sequences in the host organisms. In the laboratory, synthetic plasmids are incorporated into the host cell. by the process of transformation.

To serve the purpose of self-replication, the plasmid having a small piece of DNA which act as a site for origin of replication. The self-replicating unit in plasmids is known as replicon. The bacterial replicon consists of genes for many repeating units called iterons, plasmid specific replication initiation proteins, adjacent AT-rich region and DnaA boxes.

Illustration of plasmid in Bacterial cell from Wikipedia

The bacterial plasmids are broadly classified on the basis of it function.

  • F-plasmid – F stands for fertility. F-plasmid having tra genes, results in the expression of sex pili.
  • R-plasmid – R stands for resistance. It is the plasmids having genes that resistance to poisons or antibiotics.
  • Col-plasmids – it is the plasmid having genes for bacteriocins (protein that kill the other bacteria).
  • Degradative plasmids – this plasmid can digest unusual substances, e.g. salicylic acid and toluene.
  • Virulence plasmid – it is the plasmids having genes that turns bacteria into pathogen, e.g. in Agrobacterium tumefaciens, Ti plasmid responsible for virulence.

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