Cell differentiation

Newly formed cells are undifferentiated. That is, they are stem cells and have not yet become specialised in a process called cell differentiation.

Large, multicellular organisms like humans are made from many different cell types. There are over 200 specialised cells in our bodies. So, stem cells must differentiate so that they develop the features that enable them to fulfil their specific roles. Once they have specialised, they are unable to change into other cell types.

Specialised cells in animals

Cells of the…Specialised to…
Circulatory systemTransport substances, defend the body, regulate temperature
Excretory systemRemove waste products and unwanted substances, regulate the water content of the body
Muscular system Bring about movement
Nervous system Respond to internal and external stimuli and conditions, carry messages for the body to work as a coordinated whole
Respiratory system Deliver oxygen for respiration and remove waste
Reproductive system Bring about fertilisation to produce new offspring
Skeletal system Bring about movement, support and protect internal structures, produce blood cells, store and release calcium

Specialised cells in plants

Cells of the...Specialised to...
LeafPalisade mesophyllCarry out photosynthesis
Spongy mesophyllAllow gases to circulate for the exchange of gases between the leaf and the environment, carry out some photosynthesis
Guard cellsOpen and close to control the exchange of gases – carbon dioxide, water vapour and oxygen
PhloemSieve tubes Transport products of photosynthesis, including sugars and amino acids, from the leaf to where they are needed
Companion cellsProvide the energy required for transporting substances in sieve tubes
XylemXylem vesselsTransport water and dissolved minerals from the roots, up the plant
Growing pointsMeristemProduce new cells as they divide

Stem cells

Find out where stem cells come from and how they are used in humans and plants

Stem cells are cells that have not undergone differentiation. An embryo develops from a fertilised egg. Cells at early stages in the development of the embryo are stem cells.

If cells are removed from the embryo – called embryonic stem cells – they will differentiate into any cell type.

Some stem cells remain in the bodies of adults – adult stem cells.

Adult stem cells are found in limited numbers at certain locations in the body, including the:

  • brain
  • eyes
  • blood
  • heart
  • liver
  • bone marrow
  • skin
  • muscle

Adult stem cells can differentiate into related cell types only, for example, bone marrow cells can differentiate into blood cells and cells of the immune system but not other cell types.

Stem cells in plants

Cell division in plants occurs in regions called meristems.

Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant.

The main meristems are close to the tip of the shoot, and the tip of the root.

Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant.  The main meristems are close to the tip of the shoot, and the tip of the root.

In a growing shoot, new cells are being produced continuously near the tip. As the cells become older, further away from the tip, they become differentiated – they enlarge and develop vacuoles.

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