- Define and explain Specialised Cells in your own words
- Use key terms such as stem cell accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Specialised Cells: see how root hair cells, sperm cells, red blood cells and neurones are adapted to their jobs.
See how root hair cells, sperm cells, red blood cells and neurones are adapted to their jobs.
Key ideas
Specialised cells
Cells differentiate to suit their function. Root hair cells have long hairs that increase surface area for absorbing water. Sperm cells have a streamlined head, many mitochondria for energy, and a tail for swimming. Red blood cells have no nucleus, leaving maximum space for haemoglobin to carry oxygen, and a biconcave shape that increases surface area. A cell's structure always matches its job.
Microscopes and magnification
A light microscope uses light and glass lenses to magnify specimens up to about 1500 times. Electron microscopes reach far higher magnifications and resolution but cannot view living cells. Magnification is calculated with: magnification = image size ÷ real size. Always convert both measurements to the same units before dividing, for example millimetres to micrometres (1 mm = 1000 μm).
Key term — stem cell: An unspecialised cell that can divide to produce more stem cells or differentiate into specialised cell types.
Why do red blood cells have no nucleus?
Losing the nucleus leaves more space for haemoglobin, so each cell can carry as much oxygen as possible.
Answer: Losing the nucleus leaves more space for haemoglobin, so each cell can carry as much oxygen as possible.
- Saying mitosis produces different cells Mitosis produces two genetically identical cells. It is meiosis, used to make gametes, that produces variation.
- Confusing magnification with resolution Magnification makes things bigger; resolution makes them clearer. A blurry image magnified 1000 times is still blurry.
Practice
The hair increases the cell's surface area, so it can absorb water and mineral ions from the soil more quickly.
Mitochondria release energy by respiration. The sperm needs large amounts of energy to swim towards the egg, so many mitochondria supply it.
Any two of: growth (increasing cell number); repair of damaged tissue; replacement of worn-out cells.
Oxygen concentration is higher in the air sacs than in the blood, so oxygen diffuses down its concentration gradient into the blood.
Quick check
Which of these best defines "stem cell"?
A cell image is 40 mm wide at ×200 magnification. What is the real width in mm?
- Specialised Cells: see how root hair cells, sperm cells, red blood cells and neurones are adapted to their jobs.
- Specialised cells: Cells differentiate to suit their function.
- magnification: How many times larger an image appears compared with the real object, calculated as image size divided by real size.
- Watch out for: saying mitosis produces different cells