Describe cell differentiation and identify how cells become specialised.
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GCSE Biology Revision
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GCSE Biology revision
Cell differentiation
Cell structure
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Explain how differentiation produces specialised cells with sub-cellular structures suited to their functions.
Compare differentiation in animals and plants and explain its significance for growth, repair and replacement.
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Key knowledge
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Fertilisation: The Starting Point
- When a sperm cell and egg cell fuse, their nuclei join together to form a fertilised egg, which is the very first cell of a new individual.
- The fertilised egg contains all the genetic information needed to produce every type of cell in the body.
Early Cell Division and Stem Cells
- After fertilisation, the egg divides repeatedly — first into 2, then 4, then 8 cells — forming a ball of very similar cells.
- These early cells are called embryonic stem cells and are described as undifferentiated, meaning they do not yet have a specialised function.
- The 8-cell stage is typically reached by around three days after fertilisation.
What Does Cell Differentiation Mean?
- Cell differentiation is the process by which undifferentiated cells develop into specialised cells with specific structures and functions.
- During differentiation, cells begin to produce the particular sub-cellular structures they need, such as mitochondria, to carry out their specific role.
- Once a cell has the sub-cellular structures required for a particular function, it is described as a specialised cell.
Examples of Specialised Cells
- Muscle cells are one example of a specialised cell; groups of muscle cells form muscle tissue capable of contracting.
- Nerve cells (neurones) are specialised to rapidly transmit electrical signals around the body.
- Epithelial cells are thin, flat cells that fit tightly together with no gaps, making them ideal for covering organs and tissues inside the body.
From Cells to Organisms
- Specialised cells group together to form tissues, which combine to form organs, which work together as organ systems, ultimately making up the whole organism.
- This hierarchy — cell tissue organ organ system organism — is fundamental to understanding how living things are organised.
Limits of Differentiation in Animal Cells
- After differentiation in animals, cells lose their ability to change into a different cell type — for example, muscle cells cannot become nerve cells.
- Cell division in differentiated animal cells is limited to repair, reproduction, or producing more of the same cell type during growth.
Differentiation in Plants
- Unlike animals, many cells in adult plants retain the ability to differentiate throughout the plant's life.
- Cells that can still differentiate in adult plants are found in regions called meristems, and the tissue in these regions is called meristematic tissue.
- Meristematic tissue is located at the shoot tip, root tips, and near side branches of the plant.
- In theory, cells from meristematic regions can differentiate into any other type of plant cell.
Why Is Cell Differentiation Important?
- Cell differentiation is essential because it produces specialised cells that can carry out specific functions required for an organism to survive.
- Without differentiation, tissues and organs with the correct structures could not form, and the organism would be unable to function normally.
Key Vocabulary Summary
- Undifferentiated describes cells that have not yet developed a specialised structure or function, such as embryonic stem cells.
- Sub-cellular structures, such as mitochondria, are the components produced during differentiation that enable a cell to carry out its specific role.
- Meristematic tissue is the plant equivalent of stem cells — regions where cells retain the ability to differentiate in the adult organism.