What is Protoplasm?

Protoplasm could be defined as the living parts of the cell. Protoplasm is used to describe all the living substances present within the cell. The protoplasm provides the stage for all the cellular processes to take place. The term protoplasm is not used so much extensively currently as it is mainly replaced by terms like cytoplasm, and nucleus.

What is Protoplasm?

In the year 1846, Hugo von Mohl used the term "protoplasm" for the first time. Protoplasm can be defined as a living substance that plays a very important role in various processes of the cell. It consists of the cell cytoplasm along with the cell organelles. The plant protoplasm is surrounded by the cell membrane and the cell wall whereas the animal protoplasm is surrounded by the cell membrane. It is a mixture of organic and inorganic components. It is essential for the survival and functioning of all living organisms.

Prokaryotic Protoplasm

A prokaryotic cell lacks a defined nucleus and various cytoplasmic organelles. The cytoplasmic content of a cell is called the prokaryotic protoplasm, which is present inside the plasma membrane (excluding the plasma membrane). In the case of Gram-negative bacteria, the protoplasm includes the periplasm, a gel-like fluid content present in the space between the inner cytoplasmic membrane and the outer membrane.

Eukaryotic Protoplasm

Eukaryotic protoplasm could be defined as cytoplasmic content (including all the types of organelles single or double membranes and cytosol) and the nucleus (containing nucleolus and nucleoplasm) present inside the plasma membrane.

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Features of Protoplasm

The key features of protoplasm are;

• The protoplasm is composed of a complex mixture of various organic and inorganic molecules like water, ions, proteins, lipids, etc.
• The major component of protoplasm is water which makes up a significant percentage of its mass.
• All the metabolic processes of the cell take place in the protoplasm.
• Protoplasm can respond to environmental stimulus or changes in its internal conditions.
• Protoplasm helps in cell division, increase in size, and cellular repair.
• It helps in maintaining the internal homeostasis of the cell.
• Protoplasm is covered by the cell membrane which has a selective permeability.
• It helps in the facilitation of the movement of substances within the cell.

Structure of Protoplasm

Protoplasm has a dynamic structure that is composed of various components that perform various cellular functions. The structure of protoplasm can be described as;

Cell Membrane/Plasma Membrane

It is the outermost layer of the cell. It is made up of a lipid bilayer and regulates the transfer of substances throughout the cell due to its selective permeability.

Cytoplasm

It is a semi-fluid matrix that fills up the interior of the cell. It consists of cytosol is fluid part of the cytoplasm, and cell organelles like the endoplasmic reticulum, mitochondria, Golgi apparatus, cell inclusions, etc.

Nucleus

It is a membraned structure that consists of the genetic material i.e. the DNA, and RNA of the cell along with various proteins. These are the regions where all the cellular activities are controlled.

Protoplast

The protoplast could be defined as the combination of protoplasm and ergastic bodies, excluding the plasma membrane. In the biotechnology world, protoplast fusion has great applications. It could be used for the generation of cybrids, gene transfer, plant virus infection, etc.

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Components of Protoplasm

The protoplasm is made up of a complex mixture of components that work in tandem to provide all the necessities for the survival of the cell. These components are categorized into two main groups;

Organic Components

These are the hydrocarbon-based components that play a significant role in the cellular processes;

• Proteins: They are made of chains of amino acids. They are used in various cellular functions like structural components, transporters, hormones, and enzymes.
• Nucleic Acids: It consists of DNA and RNA that carry the genetic material of the cell.
• Lipids: It consists of fats, phospholipids, and steroids. It helps in the formation of many structural components of the cell, energy storage, and cell insulation.
• Carbohydrates: They include short-chained and long-chained sugars. They are the main substrates for energy synthesis.

Inorganic Components

These are other non-hydrocarbon-based components that are part of a cell protoplasm. It includes;

• Water: It forms the majority of the cell's mass. It acts as a solvent for various biochemical reactions and provides a medium for various cellular processes.
• Ions: Inorganic ions include; Na⁺, K⁺, Ca²⁺, and Cl^-. These ions help in various processes like cellular homeostasis, transmitting nerve signals, and regulating muscle contractions.
• Minerals: Inorganic minerals include; Fe, Mg, and P. These minerals are essential for cell development and various other processes.
• Inorganic Compounds: Certain other inorganic compounds like CO₂, and O₂ are essential cellular responsible.

Functions of Protoplasm

Protoplasm has a wide range of essential functions that include;

1. Various metabolic processes like energy synthesis, breakdown of waste products, etc.
2. It helps in the generation of energy through the processes like cellular respiration, and photosynthesis.
3. It helps in the synthesis of proteins, lipids, carbohydrates, and nucleic acids.
4. It helps in the movement/transport of substances to and from cells.
5. It helps in the elimination of wastes from the cell.
6. It helps the cell to respond to the environmental stimuli.
7. It helps in the process of cellular growth and reproduction.
8. It helps to maintain the cellular integrity and structure.
9. It helps the cell to perform cell-to-cell interactions.
10. It also consists of components that help in cellular defense.

Protoplasm Vs Cytoplasm

Difference between Protoplasm and Cytoplasm are given below:

Protoplasm	Cytoplasm
Protoplasm could be defined as the living components of the cell, including the cytoplasm and nucleus, except the non-living ergastic bodies.	Cytoplasm could be defined as living entities of the cell; for example, cytoplasmic organelles and the cytosol, except nucleus and ergastic bodies.
It consists of all the cytoplasmic organelles, cytosol, and nucleus.	It consists of cytoplasmic organelles and cytosol.
It is a thick and translucent fluid-like structure consisting of amino acids, proteins, nucleic acids, carbohydrates, lipids, and other inorganic substances.	It is a jelly-like fluid consisting of water, proteins, and other metabolic waste.