Eukaryotic Cell Organisation (AQA A Level Biology)
Revision Note
Written by: Lára Marie McIvor
Reviewed by: Lucy Kirkham
The Organisation of Cells
As seen on the last page, in complex multicellular organisms eukaryotic cells become specialised for specific functions. For example:
Epithelial cells in the small intestine are specialised to absorb food efficiently
Red blood cells are specialised to transport oxygen
In multicellular organisms, specialised cells of the same type group together to form tissues
A tissue is a group of cells that work together to perform a particular function. For example:
Epithelial cells group together to form epithelial tissue (the function of which, in the small intestine, is to absorb food)
Muscle cells (another type of specialised cell) group together to form muscle tissue (the function of which is to contract in order to move parts of the body)
Different tissues work together to form organs. For example:
The heart is made up of many different tissues (including cardiac muscle tissue, blood vessel tissues and connective tissue, as well as many others)
Different organs work together to form organ systems
Examples of specialised cells being organised into tissues, tissues into organs and organs into organ systems:
Examiner Tips and Tricks
It’s important to start learning some biological examples of each of these levels of organisation. Try and start with an organ system, such as the circulatory system or nervous system, and work your way down the levels of organisation noting down examples of organs, tissues and specialised cells as you go! Alternatively, start with a specialised cell you know of, such as a red blood cell, and work your way up the levels of organisation until you reach an organ system.
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