Cell differentiation

In the syllabus and the exam

Cell differentiation explains how a multicellular organism, which begins as a single fertilised cell, ends up with a wide range of different cell types, each suited to a different job; the syllabus links it directly to mitosis, since repeated mitotic division first produces genetically identical, unspecialised cells before some of them differentiate. Typical exam questions ask candidates to describe how a named cell's structure results from differentiation, for example explaining that a red blood cell loses its nucleus and becomes biconcave in shape to maximise the surface area available for carrying oxygen, or that a sperm cell develops a tail and an unusually large number of mitochondria to swim efficiently and supply energy for movement. A common error is treating cell differentiation and mitosis as the same process; mitosis is the division that produces new cells, while differentiation is the separate process by which some of those new cells change in structure and function afterwards, and a cell can complete mitosis without ever differentiating further. Candidates are also expected to know that differentiation is generally permanent in humans (a fully differentiated nerve cell does not usually revert to an unspecialised state), which is why damage to highly specialised tissue, such as nerve tissue, is difficult for the body to repair by producing brand-new specialised cells of the same type. Exam questions on this term often pair a labelled diagram of a specialised cell with a request to link two or three visible structural features directly to the cell's function, so candidates should practise writing feature-and-reason pairs rather than describing the cell's appearance alone.

Example

An unspecialised cell in a plant's root tip meristem may undergo cell differentiation to become a root hair cell, growing a long extension that increases its surface area for absorbing water.

Related terms

TissueCellMitosis

Source:SRC-DSKP-EN