Cell differentiation and specialised cells

Biology · Cell differentiation

One cell, five futures

Pick a route for this cell and follow it to the end. Then go back and try another.

Route taken

On Embryonic stem cell. 5 branches to choose from.

Mitosis has made lots of identical embryonic stem cells from one zygote. Now it's time for each one to find a job.

Biology · Cell structure

Choose a cell under View, then tap one of its parts under Explore.

Muscle cell: many mitochondria for contraction.

Pick a cell, then tap the part that makes it good at its job.

What you need to know

• Every cell in your body has the same DNA, whatever job it does.
• A gene is a short section of DNA that codes for a protein.
• In a specialised cell, different genes are switched on, so it makes just the proteins its job needs.
• Have a goYour friend Sam says: 'A skin cell and a nerve cell look nothing alike, so they must have different DNA.' What do you tell Sam?

  Same DNA. The cells differ because different genes are switched on.

  Looking different doesn't mean different DNA: it comes from which genes are used, and so which proteins the cell makes.

• Differentiation is how an unspecialised cell becomes a specialised cell.
• Mitosis makes identical copies of a cell. Differentiation is what makes cells different from each other.
• Have a goMitosis has just given you two new cells. Which process could turn one of them into a muscle cell rather than another copy?

  Differentiation.

  Mitosis only makes identical copies; changing a cell's job is what differentiation does.

• A muscle cell has many mitochondria for contraction.
• A palisade cell is full of chloroplasts to trap sunlight; a phloem cell has no nucleus, leaving space for moving sugars.
• Have a goUnder the microscope you see a plant cell packed with chloroplasts. What job does that suggest for it?

  Trapping sunlight for photosynthesis, like a palisade cell.

  Chloroplasts are the structure that traps sunlight; the other cells you met use mitochondria or empty space for other jobs.

• Similar cells doing one function form a tissue. Different tissues working together form an organ, and organs working together form an organ system.
• Embryonic stem cells can become all types of cell. Adult stem cells, like those in bone marrow, can become most but not all.
• Growth is more cells made by mitosis. Development is specialised cells made by differentiation, forming tissues and organs.

The big picture

Every cell has the same DNA. Mitosis makes identical copies; differentiation is what turns unspecialised cells into specialised ones, by switching on different genes. Specialised cells are adapted to their job, and cells are organised into tissues, organs and organ systems. Stem cells are the unspecialised ones: embryonic stem cells can become all types of cell, adult stem cells most but not all.

⚠ Watch out

Thinking specialised cells have different DNA, or that mitosis makes the different kinds of cell. All cells have the same DNA. Mitosis makes identical copies; differentiation switches different genes on, which is what makes cells different.

Memory hook

Same instruction book in every cell, different pages open. Mitosis copies the book; differentiation decides which pages get used.

Check yourself

Without looking back: why could mitosis alone never turn one zygote into a body containing muscle cells, nerve cells and fat cells? Say what mitosis does and what has to happen as well.