Introduction

Cytosol and cytoplasm both are broad terms that define the cell infrastructure. But these terms are often subject to confusion as they sound somewhat similar. Cytoplasm is a quite famous term, everything else in the cell except the nucleus is Cytoplasm. But what makes it the cytoplasm is its watery fluid called cytosol. In this article, we are going to lay down a differential description of Cytosol vs Cytoplasm.

Cytosol

• “Cytosol” from Greek origin consists of “cyto” meaning “cell” and “sol” meaning “solution” or “fluid”.
• Cytosol is the main watery fluid inside the cell that is surrounded by the cell’s boundary and has a jelly-like consistency.
• It is also known as the aqueous phase or matrix of the cell.
• The cytosol is present within the cytoplasm occupying the space between the nuclear envelope and plasma membrane.
• The cytosol is found in all types of cells, comprises about 20-25% of the total protein content of the cell and contains soluble proteins and enzymes (1).

 Cytoplasm

• The entire region between the nucleus and the plasma membrane is called the cytoplasm, meaning the cytosol is part of the cytoplasm. The cytoplasm is nothing but Cytosol plus Membrane-bound Cell organelles.
• The term “cytoplasm” is derived from the Greek words “kýtos” meaning “cell” and “plásma” meaning “something moulded or formed.” The word was first introduced by the German anatomist Rudolf Virchow in 1858.
• It consists of water, proteins, enzymes, different types of RNA molecules and reserve materials like glucogen, volutin and sulphur.
• The dense nuclear areas of cytoplasm contain 70S ribosome granules, composed of RNA and protein and are the site of protein synthesis (2).

Functions of Cytosol

• Cytosol is responsible for chemical activities and energy transformations in the cell.
• It collects essential nutrients from the surroundings through diffusion and active transport.
• Cytosol supplies nutrients to organelles through ionic transport.
• It assists in the removal of waste products from the cell.
• Cytosol is the site of glycolysis which is the initial step of cellular respiration.
• Cytosol helps distribute useful energy and dissipate heat in cellular energy transactions.
• It plays a key role in protein production, sorting, and transportation.
• All plant proteins are synthesised by ribosomes in the cytosol.
• Cytosol provides a medium for transporting messenger RNA (mRNA) to ribosomes for protein synthesis (3).

Functions of Cytoplasm

The cytoplasm assumes the following crucial function in a cell

• Protein synthesis: cytoplasm houses ribosomes which are responsible for protein synthesis.
• Energy generation: The cytoplasm hosts metabolic pathways, such as glycolysis and specific stages of cellular respiration, leading to the production of ATP (adenosine triphosphate), which acts as the primary energy source for cells.
• Signal transduction: Signalling molecules can transmit signals through the cytoplasm, thus regulating cellular processes. This includes relaying signals from the cell membrane to the nucleus, controlling gene expression, and regulating other cellular responses.
• Metabolite and molecule transportation: The cytoplasm provides a medium for transporting metabolites, ions, and molecules between different organelles within the cell.
• Maintenance of organelle structure: The cytoplasm serves as a structural framework for organelles like the nucleus, mitochondria, endoplasmic reticulum, and others.
• Cellular structural support: The cytoplasm contributes to the overall structural integrity of the cell by providing mechanical support, shape, and organisation (3).

Structure of Cytosol and Cytoplasm

A- Everything in the cell except the Nucleus is called Cytoplasm

(Cytoplasm= Cytosol + Organelles + Cytoskeleton + Granules)

B- The blue watery fluid in the cell between the organelles is called Cytosol

Cytosol vs Cytoplasm

• Cytosol is the intracellular matrix or the liquid part of the cell while on the other hand, the cytoplasm is the collective volume inside a cell, excluding the nucleus, possessing the cytosol and organelles.
• The cytosol is where metabolic reactions happen in prokaryotes, while larger activities like glycolysis and cell division occur in the cytoplasm.
• The cytosol has concentration gradients, protein complexes, protein compartments, and cytoskeletal sieving. These things are not separated by cell membranes but are organised in specific areas within the cytosol.
• On the other hand, the cytoplasm is made up of three main things: cytosol, cell organelles, and inclusions.
• The cytosol is mostly water with dissolved ions, large molecules, small molecules, and proteins. It’s a complex solution that has all the molecules needed for metabolism.
• The cytoplasm consists of approximately 80% water and is composed of various components such as nucleic acids, enzymes, lipids, inorganic ions, amino acids, carbohydrates, and lightweight compounds.
• Additionally, it contains dissolved salts and nutrients which facilitate the absorption of water by the cell (4).

Well to describe the differences between Cytoplasm and cytosol in a fun manner here lies the conversation between the two

• Cytosol: Hey Cytoplasm, did you know that I’m the liquid portion of the cell?

• Cytoplasm: Absolutely, Cytosol! But I encompass much more than that. I am the entire contents of the cell, including organelles and structures.

• Cytosol: That’s true. I mainly consist of water and dissolved solutes like ions, amino acids, and sugars. I play a significant role in metabolic reactions like glycolysis and protein synthesis.

• Cytoplasm: Besides your composition, I also contain membrane-bound organelles such as the nucleus, mitochondria, and endoplasmic reticulum. These organelles have specialised functions within me.

• Cytosol: While you have organelles, I don’t. Instead, I provide a medium for cellular processes like signal transduction and enzyme activity. I contribute to maintaining cell shape and structure too.

• Cytoplasm: That’s fascinating! I provide support and shape to the cell through my various organelles. Additionally, I have enzymes specific to each organelle that help carry out specific functions.

• Cytosol: I may not have ribosomes, but I allow for the diffusion of small molecules. I’m also involved in intracellular transport and molecular trafficking.

• Cytoplasm: Ah, ribosomes! They are one of my components. They are responsible for protein synthesis. Moreover, I contain compartments that facilitate specific cellular functions, ensuring efficient processes within the cell.

Q&A

1. How much cytoplasm is in a cell?

The proportion of cytoplasm in different cells varies according to its type, although it roughly constitutes 70 % of the cell volume.

2. Are cytosol and cytoplasm the same?

No, they are different, Cytosol is the intracellular matrix or the liquid part of the cell while on the other hand, the cytoplasm is the collective volume inside a cell, excluding the nucleus, possessing the cytosol and organelles.

3. How are cytoplasm and cytosol related?

Cytosol is the part of the cytoplasm, it forms the liquid portion of the cell which falls in the cytoplasmic region.

4. What is cytosol vs cytoplasm?

Cytosol is the fluid part of the cell while the cytoplasm is the entire content of the cell excluding the nucleus.

 5. Is cytosol part of cytoplasm?

Yes, Cytosol is a part of cytoplasm and constitutes the fluid part of it.

Written By: Deva Singh