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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Cell Differentiation
Cell differentiation is one of the most fascinating processes in biology. It's how a single fertilised egg cell can develop into a complex organism with many different types of cells. In humans, that's over 200 different cell types - from nerve cells to muscle cells to blood cells - all coming from one original cell!
Key Definitions:
Cells differentiate to perform specific functions efficiently. Imagine if every cell in your body tried to do everything - it would be chaos! Instead, cells specialise to become experts at particular jobs. This specialisation allows multicellular organisms to function effectively with different cells working together like a well-organised team.
During differentiation, cells activate some genes and switch off others. This selective gene expression determines which proteins the cell makes, which in turn determines the cell's structure and function. Although differentiated cells contain the same genetic material as the original cell, they only express the genes needed for their specific role.
All multicellular organisms begin life as a single cell. In humans, this is the fertilised egg or zygote. This cell divides repeatedly to form an embryo containing stem cells. These stem cells then differentiate to form all the specialised cells needed in the body.
Not all stem cells are the same. They vary in their potential to differentiate into different cell types:
Can form any cell type, including embryonic and extra-embryonic tissues (like the placenta). The zygote and early embryonic cells are totipotent.
Can form almost all cell types in the body but not extra-embryonic tissues. Embryonic stem cells are pluripotent.
Can form multiple, but limited cell types. For example, blood stem cells can form different types of blood cells but not nerve cells.
Let's look at some examples of specialised cells and how their structure relates to their function:
Scientists at the University of Edinburgh have been using stem cells to develop treatments for liver disease. By taking skin cells from patients, they can reprogram them into stem cells, then guide these to develop into liver cells. This technique could potentially allow doctors to grow "mini-livers" for testing treatments or even for transplantation. This research shows how understanding cell differentiation can lead to medical breakthroughs.
How does a cell know what to become? The process is controlled by:
During development, cells receive signals that activate or deactivate certain genes. This changes the proteins they produce, which in turn changes their structure and function. Once a cell has differentiated, it usually can't change back or become a different type of specialised cell.
While most differentiated cells can't change their type, some plants have cells that can "dedifferentiate" - return to a stem cell-like state. This is why you can grow a whole new plant from a small cutting!
Many people think all stem cells come from embryos, but adults have stem cells too! They're found in various tissues like bone marrow and fat, though they're usually multipotent rather than pluripotent.
Cell differentiation is a key part of development in multicellular organisms. The process follows these general steps:
Throughout this process, cells become increasingly specialised. Early in development, cells are more flexible in what they can become. As development progresses, their potential becomes more restricted as they commit to specific developmental pathways.
Understanding cell differentiation has led to advances in therapeutic cloning. This involves creating stem cells that are genetically identical to a patient. These could potentially be used to grow replacement tissues or organs that wouldn't be rejected by the patient's immune system. While this technology is still being developed, it shows how knowledge of cell differentiation could revolutionise medicine.
Cell differentiation is the process that allows a single cell to develop into the complex arrangement of specialised cells found in multicellular organisms. Through selective gene expression, cells develop specific structures that allow them to perform particular functions efficiently.
This process is essential for the development and functioning of all multicellular organisms. Without cell differentiation, complex life as we know it wouldn't be possible. From the nerve cells that allow you to read this text to the muscle cells that let you turn the page, differentiated cells are working together to keep you alive and functioning.
Every cell in your body (except red blood cells) contains the complete set of your DNA - the instructions to make any cell type. Yet a nerve cell doesn't try to be a muscle cell. How amazing is it that cells can selectively use just the parts of the genetic instructions they need for their specific job?
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