الأسبوع 10 · الوحدة الثالثة «الكائنات الحية تركيبها وعملياتها» (افتتاحية) والدرس الأول «الخلايا والحياة»: الخلية وأوليات النواة وحقيقيات النواة والخلايا الجذعية · 3 دروس
3
Stem cells: one kind that becomes many
Science Prep 1 Term 1, Unit 3: pp. 55–63
GoalExplain what stem cells are and discuss their hopes and questions in a balanced way.
New words
stem cell · a cell that can divide to renew itself and can become specialised cellsspecialised cell · a cell with a special shape and job, such as a nerve cellstructure and function · how a cell is built and the job it does
Explanation
Stem cells can renew themselves by dividing, and they can become different specialised cells, such as nerve, muscle, intestine and liver cells. A specialised cell has a structure that fits its function: a muscle fibre is long so it can contract and relax, and a nerve cell is long and thin so it can carry messages. A stem cell is like a lump of clay that can be shaped into a bowl, a jar or a teapot. Pottery makers in the Fustat pottery village do this every day with clay. Researchers hope that stem cells will help us understand diseases, replace diseased cells and test drugs safely. But this research raises questions about ethics, which means what is right and fair: who decides, and how can everyone be treated fairly? These are ideas to discuss, not treatments to try or advice about health.
a stem cell→divides: more stem cells→some become nerve, muscle or liver cells
Worked examples
one lump of clay→a bowl, a jar, a teapot
A lump of clay can become many shapes. In the same way a stem cell can become many kinds of cell. After it becomes a muscle cell it keeps that shape and job.
Cell
Shape
Job
nerve cell
long, thin
carries messages
muscle cell
long fibre
contracts and relaxes
Match each cell to its shape and job: a nerve cell is long and thin and carries messages, a muscle cell is long and contracts, and a red blood cell is small and moves through blood vessels.
Rania says: “Stem cells are a magic cure.” Her teacher answers: “Researchers hope they will help, but much is still being studied and there are ethical questions. For health, we ask a doctor.”
Class activity
Clay cells. With clay or dough make one round “stem cell”. Divide it into two and say that it divided. Then shape the pieces into a long thin “nerve cell”, a long “muscle fibre” and a round “red blood cell”. Hold a small discussion with a family member: what hopes do people have for stem cells, and what questions about fairness should we ask?
Practice
1
What two things can stem cells do?
Renew themselves by dividing and become specialised cells.
2
Name two kinds of specialised cell.
For example nerve cells and muscle cells.
3
What does “structure fits function” mean? Give an example.
A cell’s shape suits its job. A muscle fibre is long so it can contract and relax.
4
Give one hope and one question that people have about stem cell research.
Hope: understanding diseases or testing drugs. Question: about ethics, such as who decides and how to be fair.
