Stem cells: Treatment with stem cells may be able to help conditions such as diabetes and paralysis.

The idea

Stem cells are unspecialised cells that can divide and differentiate into many cell types. In diabetes, the insulin-secreting pancreatic cells are damaged or destroyed, so a patient cannot control blood glucose normally. In paralysis, nerve cells of the spinal cord are damaged and cannot carry impulses to muscles. Stem cell treatment aims to replace these lost cells: stem cells could be guided to become new pancreatic cells that secrete insulin, or new neurones that reconnect damaged pathways. The word 'may' is important: much of this work is still experimental, with risks such as immune rejection and uncontrolled cell division, so stem cell therapy is not yet a routine cure for either condition.

What earns the marks

• Stem cells are unspecialised and can differentiate into a range of specialised cell types.
• Diabetes involves loss or malfunction of insulin-secreting pancreatic cells, so replacing them with stem-cell-derived cells could restore glucose control.
• Paralysis can result from damage to nerve cells, so stem-cell-derived neurones might repair or bypass damaged pathways.
• Immune rejection and ethical issues are relevant limitations that affect whether stem cell treatment can be used successfully.

Common mistakes and how to put them right

• Writing that stem cells 'cure' diabetes or paralysis outright.

  Put it right by saying they may help or may be used in treatment, because the therapies are still being developed and tested.

• Confusing stem cells with fully specialised cells.

  Put it right by stating that stem cells are unspecialised and become specialised through differentiation.

• Assuming all stem cells come from embryos.

  Put it right by noting that stem cells can also come from adult tissues such as bone marrow, and that sources differ in flexibility and ethical acceptability.

Exam tips

• Link each condition to the specific cell type that is lost: pancreatic cells in diabetes and nerve cells in paralysis.
• Use the command word in the question: 'may be able to help' signals that you should discuss possibility and limitations, not certainty.
• Include one benefit and one risk or limitation, such as possible repair versus immune rejection, to show balanced understanding.