biology questionsThe cytoplasm of a cell contains both the jelly-like substance inside a cell, called cytosol, and the sub-structures of the cell itself, called organelles. Cytoplasm is just one of many components contained inside animal cells, and is one of the most important, but besides lending the cell its shape and containing its other components, what is the actual function of cytoplasm? Find out in this guide!

You can learn about cell structure and its various functions in this introduction to biology course.

Cell Structure

An animal cell is comprised of the following parts:

  1. Nucleolus
  2. Nucleus
  3. Ribosome
  4. Vesicle
  5. Rough endoplasmic reticulum
  6. Smooth endoplasmic reticulum
  7. Golgi apparatus (also called Golgi body)
  8. Mitochondrian
  9. Vacuole
  10. Lysosome
  11. Centrosome
  12. Cytoskeleton
  13. Cytosol
  14. Cell membrane

We won’t go too much into what each of these does, but for a refresher, check out this guide to some common biology vocabulary. What you do need to know is that many of these components are called organelles, meaning “little organs.” If a cell is a tiny animal, then these organelles are its internal organs, which carry out various bodily functions as organs do.

For instance, the nucleus is the largest organelle, and regulates the rest of the cell’s activities. It houses genetic material and makes up about 10% of the cell volume.

The mitochondrian, another important organelle, is like the cell’s digestive system, carrying out metabolic activities like absorbing and breaking down nutrients and generating energy for the rest of the cell, in a process called cellular respiration.

The endoplasmic reticulum is a membranous organelle that extends through the cell’s cytoplasm and works to transport materials from one part of the cell to another, which we’ll soon learn is a very important function lent, in part, by the cytoplasm itself.

For some related study material, check out this organic chemistry course.

What is Cytoplasm?

Cytoplasm is made up of three parts: cytosol, organelles, and inclusions. The organelles we have listed above, and won’t go into their specific functions. Check out this guide to biology exam questions for a run-down. For now, let’s get into what cytoplasm is.


Many of the listed organelles are contained within their own membranes, and suspended inside a fluid called cytosol, or intracellular fluid. It’s easy to confuse cytosol for cytoplasm, but they aren’t the same thing. Cytosol is just one element in the cytoplasm. It’s the liquid that exists outside the organelles, and makes for about 70% of the actual cell volume. At one point, scientists thought the molecular composition of cytosol was relatively simple, but they’ve since learned that this is not the case.

Cytosol is a mixture of water, salt, cytoskeleton and protein filaments, soluble proteins, and vaults, among other organic molecules. Some ions contained inside cytosol include:

As you can see, cytosol contains a mixture of molecules such as protein complexes, enzymes, and more. We’ll soon learn how this composition functions together to carry out metabolic functions inside the cytoplasm, allowing organelles to interact with one another. In a way, cytosol itself has no function, but allows for many other functions to take place within it, much like the larger cytoplasm network itself.

Learn the principles of chemistry in this beginner’s course.


Besides the organelles and the cytosol that they’re suspended in, the cytoplasm also contains cytoplasmic inclusions. These are non-living elements that lack membranes and metabolic functions, which exist inside the cytosol. The most common inclusions are lipid droplets, crystals, pigments, and glycogen. Learn more about these compounds in this chemistry 101 course.

Function of Cytoplasm

Below we’ll discuss some of the functions of cytoplasm in relation to its three components. For a more in-depth understanding of how an animal cell is structured, consider taking this introduction to biology course.

Cell Shape

Because of its cytosol, the cytoplasm gives the cell volume. Without cytosol, a cell would be a flat and empty membrane. This is also due to the cytoskeleton, a component of the cell structure inside the cytoplasm made up of cytoplasmic  filaments that hold the cell’s shape together. With the cytosol liquid and the cytoskeleton together, a cell has shape.

A cell having shape and volume is important because without it, its organelles might collide against each other, resulting in damage. With cytosol filling it up, the organelles are suspended in place. If one cell bumps into another cell, their inner structures are held in place and cushioned, remaining safe.

This doesn’t mean that a cell is just a big balloon of liquid with parts floating around inside, though. Like organelles, cytosol is sectioned off by membranes into little compartments.

Learn more about what makes up matter in this guide.

Material Transport

A cell having liquid volume is important because it also allows for materials inside the cell to transport between organelles more easily. This is due to something called cytoplasmic streaming, which is a process where the cytoplasm churns and creates a flow through its cytosol for materials, such as nutrients, genetic information, and metabolites, to pass through it from organelle to organelle.

Some functions that take place inside the cytosol during this time include the transportation of metabolites. One organelle might produce an amino acid, a fatty acid, or a steroid alcohol, which will be moved through the cytosol to the organelle that needs it.

Cytoplasmic streaming also allows the cell to actually move. Some cells have cilia, tiny hair-like appendages outside the cell that allow them to move. For other cells like an amoeba, the only way to move is through the process of cytoplasmic streaming.


In addition to materials transport, the liquid space between organelles also act as storage until these materials are actually needed. Within the cytoplasm are protein and oxygen cells, among other necessary building blocks, suspended in the cytosol until they can be put to use. The cytoplasm also stores metabolic waste like carbon cells, until the disposal process can be carried out.

Looking to pass your GCSE Biology exam? Check out part one  and part 2 of this GCSE biology prep course.

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