Cells are the smallest and most basic building blocks of all living organisms. A living organism can be made of one singular cell like a bacteria, or many cells like animals such as cats, dogs, humans. New cells can only be produced from existing cells.

Multiple cells of the same kind can come together to form a tissue; and these tissues come together to form an organ. When several organs work together, this is called an organ system, for example, the digestive system is an organ system.

There are different types of cells grouped under two main categories: prokaryotic and eukaryotic. While prokaryotic cells are the more basic form of a cell, eukaryotic cells are more advanced and complex.

A prokaryote is an organism that has only one cell that lacks a nucleus and any other membrane-bound organelles. For example, bacteria and archaea are prokaryotes, they are prokaryotic cells. The name prokaryote comes from a combination of the words “pro” and “kary” which means “before” and “nucleus” respectively. These are the organisms that existed before the involvement of the nucleus.

Eukaryotic cells have a nucleus with a double membrane that carries DNA. These cells are larger compared to prokaryotic cells and have membrane bound organelles. Eukaryotic cells theorized to be evolved from prokaryotic cells. Examples of eukaryotic cells include animal cells and plant cells.

A stem cell is the cell before undergoing the transition that will determine the special category of it. For example, a stem cell can turn into a cell that will serve as a building block for stomach tissue. A stem cell can turn into any type of cell and contribute to a target tissue and organ. As cited in Biology for AP® Courses, scientists in Cincinnati Children’s Hospital Medical Centre have been developing a method to manipulate stem cells in a laboratory environment to become specialized into their desired type of cells. This is a great advancement in cancer treatment especially.

To learn more about cell biology, check out this study note by our Knowunity user Micheala.

To learn more about cells with a special focus on cell cycle and division, take a look at this study note by our Knowunity user Hannah.

This flashcard set prepared by our Knowunity US Ambassador Miranda can help you study and memorise the important scientists who made significant research on cells, components of a cell, and even laboratory equipment relevant to the topic of cells in Biology.


Cells Revision, study note uploaded to Knowunity by Val, 2023.

Biology Notes for the EOC and more, study note uploaded to Knowunity by @makani_v8606, 2023.

Zedalis, Julianne, and John Eggebrecht. Biology for AP® Courses. Rice University, 2018.

Organization in the human body

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