Cytoplasm [Definition, Functions, Structure, Inclusions & Inheritance]


The cytoplasm was discovered in the year 1835 by Robert Brown and other researchers.

The cytoplasm is the semi-viscous ground substance of the cell. All the volume of such substance outside the nucleus and inside the plasma membrane is cytoplasm.

It is often described as the non-nuclear content of the protoplasm. All the cellular contents in prokaryotes are consisted of within the cell’s cytoplasm. In eukaryote organisms, the nucleus of the cell is separated from the cytoplasm. The cytoplasm is the compound of life, it works as a molecular soup and it is in the cytoplasm where all the cellular organelles are suspended and are bound together by a lipid bilayer membrane.


Structure of the Cytoplasm

The primary elements of the cytoplasm are:

  • Cytosol– a gel-like substance
  • Organelles– the cell’s internal sub-structures, and
  • Numerous cytoplasmic inclusions.
The Cytosol

The cytosol is the part of the cytoplasm that is not inhabited by any organelle. It is a gelatinous fluid, where other elements of the cytoplasm remain suspended. It primarily includes cytoskeleton filaments, organic particles, salt, and water.


Organelles imply “little organs”, that are membrane-bound. They are present inside the cell and carry out specific functions that are essential for the survival of the cell. Some of the constituents of the cell that are suspended in the cytosol are cellular organelles like mitochondria, endoplasmic reticulum, Golgi complex, vacuoles, lysosomes, and chloroplasts in plant cells.

Cytoplasmic Inclusions

The cytoplasmic inclusions include different kinds of insoluble particles or particles that remain suspended in the cytosol. Cytoplasmic inclusions are not surrounded by any membrane. They are basically granules of starch and glycogen, and they can store energy.

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A large series of inclusions exist in various cell types. The inclusions vary from calcium oxalate crystals or silicon dioxide crystals in plants to storage granules of materials like starch, glycogen, etc. Lipid droplets are a widespread example of inclusions, these are round beads, they are made from lipids and proteins and are present in both prokaryotes and eukaryotes as a medium to store lipids like fatty acids and sterols.

Properties of Cytoplasm
  • The cytoplasm is made from 70%– 80% water and is usually colorless.
  • It includes proteins, carbs, salts, sugars, amino acids, and nucleotides.
  • The cytoplasm makes up of dissolved nutrients and likewise dissolved waste products.
  • The outer clear and glassy layer of the cytoplasm is called the ectoplasm or the cell cortex and the inner granular mass is called the endoplasm.
  • The peripheral zone of the cytoplasm is a thick and jelly-like substance, known as the plasmogel. The surrounding area of the nuclear zone is thin and liquefied in nature and is called the plasmasol.


  • The physical nature of the cytoplasm is variable. In some cases, there is quick diffusion across the cell, making the cytoplasm resemble a colloidal solution. At other times, it appears to take on the properties of a gel-like or glass-like compound.
  • It is stated to have the properties of viscous along with flexible products– capable of deforming slowly under external force in addition to restoring its initial shape with very little loss of energy.
  • The cytoskeleton present in the cytoplasm provides the cell its shape.
  • Since the cytoplasm constitutes numerous salts, it is a very good conductor of electrical energy.
  • It shows differential staining properties, the areas stained with the basic and standard dyes are the basophilic areas of the cytoplasm and is described as ergatoplasm for this material.
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Functions of Cytoplasm
  • The cytoplasm is the site for the majority of the enzymatic reactions and metabolic activity of the cell. Cellular respiration starts in the cytoplasm with anaerobic respiration or glycolysis. This reaction provides the intermediates that are used by the mitochondria to create ATP. In addition, the translation of mRNA into proteins on ribosomes also occurs mainly in the cytoplasm. Some of it happens on totally free ribosomes suspended in the cytosol while the rest occurs on ribosomes anchored on the endoplasmic reticulum.
  • The cytoplasm likewise includes the monomers that go on to create the cytoskeleton. The cytoskeleton, in addition to being very important for the normal activities of the cell, is crucial for cells that have a specialized shape. For example, neurons with their long axons need the existence of intermediate filaments, microtubules, and actin filaments in order to supply a stiff structure for the action capacity to be transferred to the next cell. Additionally, some epithelial cells contain little cilia or flagella to move the cell or get rid of foreign particles through the collaborated activity of cytoplasmic extrusions formed through the cytoskeleton.
  • The cytoplasm also plays a role in producing order within the cell with specific areas for different organelles. For instance, the nucleus is typically seen towards the center of the cell, with a centrosome close-by. The substantial endoplasmic reticulum and Golgi complex are also put in relation to the nucleus, with the vesicles radiating out towards the plasma membrane.
Cytoplasmic Streaming

Motion within the cytoplasm likewise happens in bulk, through the directed movement of cytosol around the nucleus or vacuole. This is particularly essential in large single-celled organisms such as some types of green algae, which can be nearly 10 cm in length.

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Cytoplasmic streaming is also essential for positioning chloroplasts close to the plasma membrane to enhance photosynthesis and for distributing nutrients through the entire cell. In some cells, such as mouse oocytes, cytoplasmic streaming is expected to have a function in the development of cellular sub-compartments and in organelle placing too.


Cytoplasmic Inheritance

The cytoplasm plays host to two organelles that contain their own genomes– the chloroplast and mitochondria. These organelles are acquired straight from the mother through the oocyte and therefore constitute genes that are inherited outside the nucleus.

These organelles reproduce independent of the nucleus and respond to the requirements of the cell. Cytoplasmic or extranuclear inheritance, therefore, forms an unbroken hereditary line that has actually not gone through blending or recombination with the male parent.


Cytoplasm is the semi-viscous fluid present within the cell. The cytoplasm has two distinct parts. The cytomembrane system consists of well-defined structures such as endoplasmic reticulum, Golgi apparatus, vacuoles and vesicles.

The fluid cytosol suspends the structures of the cytomembrane system. It also contains various dissolved molecules.

The cytosol majorly composed of water and salts but in addition carbon, hydrogen and other elements which are essential for metabolic activities are present in cytosol.

The processes like glycolysis, synthesis of protein and cellular divisions i.e., mitosis and meiosis occur in cytoplasm.

It is also responsible for the holding of organelles and provides transportation to organelles and vesicles by cytoplasmic streaming.