Cell differentiation

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

Large, 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 system	Transport substances, defend the body, regulate temperature
Excretory system	Remove 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

Cells of the…	Circulatory system
Specialised to…	Transport substances, defend the body, regulate temperature

Cells of the…	Excretory system
Specialised to…	Remove waste products and unwanted substances, regulate the water content of the body

Cells of the…	Muscular system
Specialised to…	Bring about movement

Cells of the…	Nervous system
Specialised to…	Respond to internal and external stimuli and conditions, carry messages for the body to work as a coordinated whole

Cells of the…	Respiratory system
Specialised to…	Deliver oxygen for respiration and remove waste

Cells of the…	Reproductive system
Specialised to…	Bring about fertilisation to produce new offspring

Cells of the…	Skeletal system
Specialised to…	Bring about movement, support and protect internal structures, produce blood cells, store and release calcium

Specialised cells in plants

	Cells of the...	Specialised to...
Leaf	Palisade mesophyll	Carry out photosynthesis
	Spongy mesophyll	Allow gases to circulate for the exchange of gases between the leaf and the environment, carry out some photosynthesis
	Guard cells	Open and close to control the exchange of gases – carbon dioxide, water vapour and oxygen
Phloem	Sieve tubes	Transport products of photosynthesis, including sugars and amino acids, from the leaf to where they are needed
	Companion cells	Provide the energy required for transporting substances in sieve tubes
Xylem	Xylem vessels	Transport water and dissolved minerals from the roots, up the plant
Growing points	Meristem	Produce new cells as they divide

Leaf
Cells of the...	Palisade mesophyll
Specialised to...	Carry out photosynthesis


Cells of the...	Spongy mesophyll
Specialised to...	Allow gases to circulate for the exchange of gases between the leaf and the environment, carry out some photosynthesis


Cells of the...	Guard cells
Specialised to...	Open and close to control the exchange of gases – carbon dioxide, water vapour and oxygen

Phloem
Cells of the...	Sieve tubes
Specialised to...	Transport products of photosynthesis, including sugars and amino acids, from the leaf to where they are needed


Cells of the...	Companion cells
Specialised to...	Provide the energy required for transporting substances in sieve tubes

Xylem
Cells of the...	Xylem vessels
Specialised to...	Transport water and dissolved minerals from the roots, up the plant

Growing points
Cells of the...	Meristem
Specialised to...	Produce new cells as they divide

Stem cells

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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 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 – they will differentiate into any cell type.

Some stem cells remain in the bodies of adults – .

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, cells can differentiate into blood cells and cells of the but not other cell types.

Stem cells in plants

Cell division in plants occurs in regions called .

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 .