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Cytoplasm can be defined as a thick solution that fills each cell and is enclosed by the cell membrane. It is mainly composed of water, salts, and proteins. In eukaryotic cells, the cytoplasm includes all of the material inside the cell and outside of the nucleus.

Fundamentally cytoplasm is the constituent that occupies the space of the cell. It is a jelly-like constituent and it is 80% water and is generally pure and pale. It melts when it is frantic or stirred. Cytoplasm is stated as cytosol, which implies ingredient of the cell. The cell membrane surrounds the cytoplasm and it also surrounds the nucleus and the cellular organelles. Cytoplasm comprises of the cytoskeleton which provides the cell its shape. The cytoplasm is made of liquefied nutrients and it supports to dissolve discarded products. It aids the motion of the cellular constituents around the cell by a process termed as cytoplasmic streaming. Cytoplasm also contains several salts and is a good conductor of electricity.


Cytoplasm definition:

Cytoplasm is a jelly like substance of a cell which is present within the plasma membrane surrounding the nuclear membrane. It is sometimes defined as extra-nuclear constituent of the protoplasm. All the cellular fillings in a prokaryote are confined inside cell's cytoplasm. On the other hand in eukaryote organisms, the nucleus is separated from the cytoplasm by a nuclear envelope. Cytoplasm is a dense and semi-transparent liquid. The cytoplasm was exposed in 1835 by Robert Brown.

Characteristics of cytoplasm:

There are many characteristics of cytoplasm which can be counted some as follows:

  • Cytoplasm is about 80% water and contains primarily proteins, carbohydrates, lipids, inorganic ions, and many lower molecular weight compounds.
  • It lacks unit membrane bound organelles in prokaryotes.
  • Bacterial cytoplasm contains 70S ribosomes while eukaryotic cytoplasm contains both 70S and 80S ribosomes.
  • It is diverse mixture of dense granules and organic complexes which provides it its colloidal environment.
  • The marginal region of cytoplasm is thick and semi fluid substance, identified as the plasmogel. The neighboring area of the nuclear region is thin and watery and is called as the plasmosol.

Bacterial cytoplasm:

The bacterial cytoplasm contains 70S ribosomes. Bacterial 70S ribosomes differ from eukaryotic 80S ribosomes present in cytosol in the number of proteins and r-RNA molecules they contain. The subunits of 70S subunits are a small subunit of 30S containing 1 molecule of r-RNA and a larger 50S subunit containing two molecules of r-RNA. Bacterial cytoplasm also contains many organic and inorganic reserve deposits known as inclusion bodies that may be membrane bound or membrane less. Example of inclusion bodies present in bacterial cytoplasm is glycogen, cynophycin granules, carboxysomes, polyphosphate molecules and others.

Bacterial Cytoplasm

Cytoplasmic structure:

Cytoplasm is the liquid where the organelles are suspended. It occupies the spaces which are not filled up by the organelles. The ingredients of cytoplasm are cytosol, organelles and cytoplasmic inclusions.


Cytosol makes up about 70%-80% of the capacity of the cell. It comprises of water, salts and organic fragments. Cytosol is made of a combination of cytoskeleton fibers, organic and inorganic compounds that are mixed in water. It also possesses protein filaments that constituents the cytoskeleton, soluble proteins and structures like ribosomes, proteasomes. The inner, more liquefied and granular region of the cytoplasm is referred as the endoplasm. The web of fibers and high absorptions of the dissolved macromolecules like proteins is responsible for macromolecular assembling.


Organelles are membrane bound cellular structures which are present in the cytoplasm. They reside inside the cell and accomplish specific functions that are essential for the existence of the cell. Some of the components of the cell that are present in the cytosol are organelles like mitochondria, endoplasmic reticulum, Golgi apparatus, vacuoles, lysosomes and chloroplasts.


Cytoplasmic Inclusions

The cytoplasmic inclusions are minute particles present in the cytosol. A massive range of inclusion bodies are present in different types of cell types. The different inclusions present are calcium oxalate crystals or silicon dioxide crystals of plants in order to store granule like starch, glycogen, etc. Lipid droplets are also example of inclusion bodies, which are spherical droplets, made of lipids and protein particles and are present in both prokaryotic and eukaryotic organisms as an intermediate to stock lipids like fatty acids and sterols. These drops occupy the volume of adipocytes which are specific storage cells, and are also found in other cell types.

Functions of cytoplasm:

  • Cytoplasm is the site where many biochemical reactions are carried out which are essential for maintaining life.
  • The cytoplasm is the site where the cell extends and expands as it grows.
  • The cytoplasm acts as a medium for the suspension of organelles.
  • The cytoskeleton present in the cytoplasm gives shape to the cell and it also aids movement.
  • It also facilitates the movement of the different cellular contents
  • The enzymes present in the cytoplasm digest the macromolecules into much small parts for their proper digestion and availability for the other cellular organelles like mitochondria.

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