Differences Between Cytosol And Cytoplasm

The cytosol is the fluid inside cells. The cell membrane surrounds the cytosol. The cytoplasm is the material inside the cell. Both cytosol and cytoplasm contain proteins, lipids, carbohydrates, nucleic acids, and other molecules.

Differences between Cytosol And Cytoplasm

They also differ in their protein composition.

In this article, we will be looking at some differences between cytosol and cytoplasm.

We will look at the different types of membranes that surround the cell and how they affect the movement of materials into or out of the cell. Also, we will discuss what happens to the contents of a cell when it dies.

Cytosol Definition

The word “cytosol” means “cell sap”. It is the liquid found inside the cell. In a living cell, the cytosol contains water, ions, small organic compounds, enzymes, and many other substances.

There are two main kinds of membranes that surround the outside of the cell: plasma membranes and organelles. Plasma membranes are thin sheets of a phospholipid bilayer that separate one part of the cell from another.

Organelles are structures within the cell that perform specialized functions such as digestion, energy production, reproduction, etc.

Membranes And Membrane Transport

Plasma membranes are made up of two layers of lipid (fat) molecules. These molecules form a barrier around the cell that prevents things from getting into or out of the cells.

This barrier keeps the cell wall strong and protects the cell against bacteria and viruses.

Plasma membranes have pores called channels that allow certain substances to pass through them. For example, there are channels for potassium ions, sodium ions, glucose, amino acids, calcium ions, etc.

These channels open and close in response to changes in the concentration of these ions in the surrounding solution.

Organelles do not have channels like plasma membranes. Instead, they have a semi-permeable membrane that allows certain substances to move in and out of the organelle.

Some examples include mitochondria, chloroplasts, lysosomes, peroxisomes, endoplasmic reticulum, Golgi apparatus, ribosomes, vacuoles, and centrioles.

Organelles can be divided into two groups based on which side of the membrane they face. The inside of the organelle is where most of the work takes place. This area is called the matrix.

The matrix has an acidic pH because it contains lots of protons. The matrix contains enzymes that break down macromolecules into smaller ones. The matrix also contains ribosomes.

Ribosomes make proteins. Proteins are large chains of amino acid monomers. They can be used by the cell to build new parts of itself.
On the outside of the organelle is the space between the membrane and the organelle’s outer wall.

This area is called intermembrane space. Intermembrane space is usually very alkaline. It contains enzymes that help with the breakdown of macromolecules into simpler ones. It also contains ribosomes and polyribosomes.

Polyribosomes contain multiple copies of each ribosome. Each copy of a ribosome makes only one protein chain. When all the ribosomes in a polyribosome finish making their single protein chains, the entire polyribosome splits apart.

Then, the individual ribosomes go back to making more protein chains.

Function Of Cytosol

Function Of Cytosol

The function of the cytosol is to provide nutrients and energy to the cell. The movement of these substances from the outside of the cell to the inside is called transport. Transport occurs through channels called transporters.

Transporters are located on the membranes of the cell. When they bind with specific molecules, they pull those molecules across the membrane.

Transport Process

When an ion binds to its transporter, it pulls the molecule across the membrane. For example, if a sodium channel binds to sodium, it will pull sodium across the membrane.

If a potassium channel binds to potassium, it will pull potassium across the membrane.

When a transporter binds to a molecule, it pulls the molecule into the cell. Then, the transporter releases the molecule so that it can be used by the cell.

Types Of Transporters

A transporter is any molecule that transports something across a membrane. There are three types of transporters: active transporters, passive transporters, and carrier transporters.

Active transporters use energy to pull molecules across the membrane. Passive transporters do not require energy. Carrier transporters carry molecules without using energy.

Active Transporter

Active transport uses energy to pull molecules across a membrane. An active transporter must have both a binding site and an exit site.

A binding site is where the transporter attaches to the molecule. An exit site is where the transporter detaches from the molecule.

Passive Transporter

A passive transporter does not need the energy to pull molecules across. Passive transporters can only attach to one side of the membrane. They cannot detach from the other side of the membrane.

Carrier Transporter

A carrier transporter carries molecules without using energy. It has no binding sites or exit sites. Carriers can only attach to one end of the membrane. They never detach from the other end of the membrane.

Composition And Properties Of Cytosol

The composition of cytosol varies depending on what kind of cell it comes from. The composition of cytosol changes during growth and development.

The cytosol contains about 98% water. Water makes up 70-80% of the weight of the human body. About 2% of the body’s mass is made up of solid substances.


Most of the water in the body is contained in the cytosol of cells. Cells use the energy stored in ATP to create an osmotic gradient across their membranes. Water then flows out of the cell into the surrounding environment.


Most of the salt and minerals in our bodies are contained in the cytosols of cells. Sodium, potassium, chlorine, bromine, and iodine are all electrolytes. Electrolytes help maintain the electrical potentials necessary for life.


Fatty acids make up most of the lipids in the body. Lipids are important because they store energy. When we eat food, the fats in the food get broken down by enzymes and absorbed into the bloodstream.

In the liver, these fats are converted into ketone bodies. Ketone bodies are used as fuel by the brain.


Protein is another major component of the body. Proteins are long chains of amino acids. Amino acids are the building blocks of protein.

There are 20 different types of amino acids. Each type has a specific function in the body. For example, glycine helps form collagen. Tyrosine forms melanin.

Cytoplasm Definition

The cytoplasm is the fluid that fills the cell. It is mostly water but also includes dissolved salts, sugars, fats, proteins, nucleic acids, and other chemicals. There are three types of cytoplasm: intracellular, extracellular, and cytosolic.

Intracellular Cytoplasm

Intracellular cytoplasm is found inside the cell. It surrounds the nucleus and organelles. It moves along the microtubules and actin filaments that run throughout the cell.

In some cells, the cytoplasm is separated into different compartments by tight junctions. Tight junctions are tiny strands of protein that connect adjacent cells.

Extracellular Cytoplasm

Extracellular cytoplasm is found outside the cell. It is part of the blood, lymph, and cerebrospinal fluids. It flows through capillaries. This type of cytoplasm is sometimes referred to as interstitial fluid.

Cytosolic Cytoplasm

Cytosolic cytoplasm is the liquid portion of the cell. It is made up of the soluble components of the cell. Soluble means that the material can flow freely around the cell.

Cytosolic cytoplasms are found within the cell and in the spaces between cells. They are often referred to as the cytosol or cytoplasm.

Function Of Cytoplasm

The main function of the cytosol is to provide nutrients and energy to the cell. The cytosol carries out metabolic processes like digestion, absorption, and excretion.

It provides the cell with the materials needed to build new structures. It transports materials from one place to another.

For example, it carries food to the stomach. It carries waste products away from the body. It helps control the temperature of the cell.


Most cells have a network of fibers called the cytoskeleton. The cytoskeleton supports the cell membrane and keeps the cell shape. It is made up primarily of two types of fibers: actin filaments and microtubules.

Actin filaments are long thin threads of protein. Microtubules are hollow tubes about 25 nanometers wide. Both types of fiber cross each other and form a complex meshwork.

The cytoskeleton holds the nucleus in place and controls the movement of organelles and chromosomes.

Cell Membrane

A cell membrane is a double layer of lipid molecules surrounding the cell. There are several types of membranes. One type surrounds all parts of the cell except the nucleus.

This is called the plasma membrane. Another kind of membrane covers only part of the cell. This is called an internal membrane. Inside the cell, there are many more membranes.

Each membrane has its special job. The outermost membrane is called the plasma membrane because it protects the rest of the cell. It allows substances to enter and leave the cell.

The next membrane is called the endoplasmic reticulum. It is involved in making proteins. The innermost membrane is called the nuclear membrane.

It separates the cell’s contents from the nuclei. It prevents anything from entering or leaving the nucleus.

Composition And Properties Of Cytoplasm

Water makes up most of the mass of the cell. Water contains H2O molecules that can be joined together by hydrogen bonds. A water molecule consists of two hydrogen atoms and one oxygen atom.

Hydrogen bonds link these atoms into a chain. If you look at a water molecule under a microscope, you will see that it looks like a rod.

Molecules of water are held together by electrostatic forces. An electric charge on a molecule causes the surrounding molecules to repel each other. When this happens, the molecules line up in columns.

In a column of molecules, the positive charges are on one side and the negative charges are on the other. The opposite charges attract each other. This creates a strong force holding the molecules together.

The cytoplasm is made up mostly of water. Other things found in the cytoplasm include:

  • Protein molecules
  • Fatty acids (lipids)
  • Nucleic acid molecules

Cytosol Vs Cytoplasm

Cytosol refers to the whole mixture of molecules that fill the cell. Cytoplasm refers to the liquid portion of the cytosol. The cytoplasm is usually much less dense than cytosol.

That is why you can see the difference when you look at the inside of a cell under a microscope.

Cytosol Molecules

There are many kinds of molecules in the cytosol. Some are small enough to fit through the pores of the nuclear envelope.

These include DNA, RNA, ribonucleoproteins (RNPs), messenger RNAs (mRNAs), transfer RNAs (tRNAs), and ribosomal RNAs (rRNAs). Other molecules are too big to pass through the pores.

These include histones, tubulin, actin, myosin, intermediate filament proteins, and lamins.

Cytoplasm Molecules

There are also many kinds of molecules in the cytoplasm. Some are small enough for the cytosol to flow through them. These include ions such as sodium, potassium, calcium, magnesium, chloride, phosphate, and hydrogen.

Other molecules are too large to move through the cytosol. These include glucose, amino acids, fatty acids, vitamins, hormones, neurotransmitters, and oxygen.

Main Differences Between Cytosol And Cytoplasm

Cytoplasm Is Denser Than Cytosol

When you compare the density of cytosol with that of cytoplasm, you find out that they are very similar. They both have about 1 gram per cubic centimeter.

However, the density of cytoplasm is slightly higher than that of cytosol. This means that cytoplasm is denser than cytosol.

Cytoplasm Has More Small Molecules

In addition to having more protein molecules, cytosol has more small molecules. For example, cytosol has about 10 times more sodium ions than does cytoplasm.

The cytoplasm also has more free amino acids. There are about 100 times more amino acids in the cytosol than there are in the cytoplasm!

Cytoplasm Contains Many Types Of Proteins

The cytoplasm has many types of proteins. For example, it has enzymes, structural proteins, transport proteins, regulatory proteins, and signaling proteins. It also has many types of nucleic acids.

Cytoplasm Contains Many Kinds Of Lipid Molecules

Cytoplasmic lipids are important because they help form membranes. They are called phospholipids. Phospholipids contain phosphorus atoms linked to carbon atoms.

They are classified into two groups: glycerophospholipids and sphingomyelin. Glycerophospholipid molecules are composed of three parts: a hydrophilic head group, a hydrophobic tail, and a polar bond.

Sphingomyelin molecules are composed of only two parts: a hydrophobic tail and a polar bond.

Cytoplasm Contains A Lot Of Water

Water makes up about 60% of the volume of cells. The rest of the water is mostly found in the extracellular space. Most of the water in your body is outside your cells.

Cytoplasm Has Fewer Large Molecules

The average size of molecules in the cytoplasm is smaller than that of molecules in the cytosis. This means that the cytoplasm contains fewer large molecules than the cytoplasm.

Final Thoughts

You should now know what the difference is between cytosol and cytoplasm. You can use this knowledge when studying cellular biology.

Knowing the difference will make it easier to understand how the cell works, which will help you learn more about life. The next time you study cellular biology, try to remember these differences!

Jennifer Dawkins