Cytoplasm - Structure And Function

Brief History of Cytoplasm

In the year 1665, Robert Hooke, an English researcher observed the fundamental unit of life through his coarse compound microscope. He coined the term “cell”, which was based on the Latin word called “Cella,” meaning, small rooms.

Later, many scientists contributed to Robert Hooke’s findings and eventually, the Cell Theory was postulated. As technology progressed, modern interpretations of Cell Theory have been formed, with new tenets and revisions of the existing ones.

In 1863, a Swiss biologist named Rudolf von Kölliker coined the term “Cytoplasm,” but it was regarded as a synonym for protoplasm. However, the term gradually changed its meaning to the current definition of the term “cytoplasm”.

Table of Contents

What is Cytoplasm?

The fluid that fills up the cells is referred to as the cytoplasm. It encompasses the cytosol with filaments, ions, proteins, and macromolecular structures and also other organelles suspended in the cytosol.

But new research suggests that the traditional definition of cytoplasm is no longer valid. Decades prior, it was considered to be a fluid-like substance, but new evidence reveals that it is similar to glass-forming liquids.

The cytoplasm in the eukaryotic cells associates with the cell contents except for the nucleus. But in prokaryotic cells, as they do not possess a defined nuclear membrane, the cytoplasm possesses the genetic material of the cell. The cells, in comparison to the eukaryotes, are smaller and have an uncomplicated arrangement of the cytoplasm.

Also Read: Difference between Karyokinesis and Cytokinesis

Cytoplasm Diagram


The cytoplasm is a fluid-like substance that fills up the cells. Cellular organelles and structures are suspended in the cytoplasm.

Cytoplasm Structure

Cell organelles are various structures existing inside cells. All these structures are distinct and perform specific functions. Cells have three main elements i.e., plasma membrane, and cytoplasm and the nucleus.

The plasma membrane or cell membrane is a bi-lipid membranous layer, parting the cell organelles from its outside environment and from the different cells. It is the external covering of a cell where all different parts, including cytoplasm and nucleus, are enclosed.

Next, is the nucleus, one of the biggest organelle. They have exclusive control of a cell. Lastly, the cytoplasm is a jelly-like material in which the cell organelles are implanted.

The cytoplasm is an essential component of the cell. It is a semi-liquid jelly-like material, which joins the nucleus and the cell membrane. In the cell, the cytoplasm is embedded, while other cell organelles such as endoplasmic reticulum, mitochondria, ribosomes, vacuoles, etc. are all suspended within it.

It can easily be examined under a microscope through the staining technique. Functionally, it is the site for several chemical reactions within a cell. Most of the cellular metabolism takes place here.

Also Refer:  Difference between Prokaryotic and Eukaryotic Cells

Cytoplasm Function

One of the major functions of cytoplasm is to enable cells to maintain their turgidity, which enables the cells to hold their shape. Other functions of cytoplasm are as follows:

  • The jelly-like fluid of the cytoplasm is composed of salt and water and is present within the membrane of the cells and embeds all of the parts of the cells and organelles.
  • The cytoplasm is home to many activities of the cell as it contains molecules, enzymes that are crucial in the break down of the waste.
  • The cytoplasm also assists in metabolic activities.
  • Cytoplasm provides shape to the cell. It fills up the cells thus enabling the organelles to remain in their position. The cells, without cytoplasm, would deflate and substances will not permeate easily from one to the other organelle.
  • A part of the cytoplasm, the cytosol has no organelles. Rather, the cytosol is enclosed by matrix boundaries that fill up the cell section which does not hold the organelles.

The whole cellular content of a living cell is called protoplasm. The cytoplasm, nucleus and all other living components of the cell together make up the protoplasm of a cell.

Further Reading: Difference Between Cytoplasm and Protoplasm


The protoplasm is generally referred to as the living part of the cell. It is the colourless, jelly-like substance composed of macromolecules, water and mixture of small molecules.  It can be defined as the inorganic and organic substance which constitutes the cytoplasm, the nucleus, mitochondria and the plastids of the cell. It is the chief substance that is responsible for all the living processes.

The primary component of the protoplasm is the cytoplasm which is situated between the nucleus and the cell membrane in the eukaryotic cells. It contains all the organelles. It regulates the environment of the cell and maintains the cell shape. It stores the substances and chemicals that are necessary for the organelle.

The second component of the protoplasm is the nucleus, which contains the genetic material of an organism and is situated in the nucleus. The nucleus contains the ribosomes that are required and are crucial for the protein synthesis in the cells.

But in the case of prokaryotes, the nucleoid is present in place of the nucleus, wherein all the genetic information is present. However, it does not have a nuclear membrane; hence, the term protoplasm does not apply.

The elements that make up the protoplasm are fats, proteins, enzymes, hormones, etc. which are either suspended or dissolved in the fluid component of the protoplasm.

Also Read: Protoplasm


The nucleus is an important element of the cells. It is a membrane-bound organelle that is typically found in the eukaryotic cells. Eukaryotes usually have a single nucleus, whereas some cell types do not possess a nucleus (RBC-Red Blood Cells).

Also Refer: Cytoskeleton

Learn more in detail about the cytoplasm, its structure, functions, other cell organelles and other related topics at BYJU’S Biology

Frequently Asked Questions


What is cytoplasm?

The cytoplasm is the fluid present in the cell enclosed within the cell membrane that comprises water and enzymes, salts, and various organelles.


What is the important function of cytoplasm?

The cytoplasm is responsible for holding the components of the cell and protects them from damage. It stores the molecules required for cellular processes and is also responsible for giving the cell its shape.


What would happen if the cell had no cytoplasm?

A cell would be deflated and flat and would not be able to retain its shape without the cytoplasm. The organelles will not be able to suspend in the cell.


What would happen if there was no nucleus in the cell?

The nucleus contains the hereditary material and is responsible for cell division. It is known as the brain of the cell and controls all its activities. Without a nucleus, the cell will not be able to perform any activity and will eventually die. There will be no replication and no synthesis of proteins.


What is the charge in the cytoplasm?

For every single ATP molecule, 3 sodium ions are exported to the extracellular space of the cell while two potassium ions are imported to the cytoplasm. Thus the cytoplasm is negatively charged.


What is the pH of cytoplasm?

The pH of the cytoplasm is 7.4.

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  1. Does the cytoplasm not have it`s own definite structure?

    • Cytoplasm does not have a definite structure. Its shape is dictated by the cell membrane or the cell wall.

    • Cytoplasm is just a fluid or in simple words it can flow. As we know liquids or fluids do not have any specific shape. However it gives shape to the cell by applying a pressure on cell membrane.


  3. Cytoplasm definition