Introduction: The specialisation of cells
- stem cells and differentiation
Undifferentiated cells are called stem cells
and develop into all the different types of cells an organism needs to
grow and develop.
A stem cell nucleus contains ALL the instructions
to switch genes 'on and off' so it has the ability to change into any
specialised cell needed by an organism.
Depending on the instructions a stem cell
receives, it can divide by
mitosis producing new cells which
can then differentiate into various types of cells for specific functions.
Multicellular organisms (eukaryotic) contain a variety of cells, with
different structures, which are adapted - specialised, to perform a
variety of functions.
Differentiation is the process by which a
cell develops into a form to do its specialised role.
Cells which have a particular structure adapted for a particular
function are called specialised cells.
After this the cells from mitosis start to
become specialised and the process of cell differentiation begins
in earnest to ensure growth and development.
Always be aware of how the cell structure and its
organelles is adapted to fulfill its function e.g. human blood
cells contain haemoglobin to transport oxygen.
In a multicellular organisms, many different types
of cell adopt different roles to ensure the organism functions correctly
in its life sustaining behaviours.
In cell differentiation, cells become
specialised by switching genes off and on to form tissues with
In the process of differentiation the stem cells
develop different sub-cellular structures to turn into the different
types of cells - specialisation.
The specialised cells can now carry out their
important specific functions - essential for the efficient and
healthy viability of any organism.
The cell's size, shape and internal structures
(e.g. organelles) must be all adapted for its function in the
The derived specialised cells include:
Bone cells in skeletal systems.
Blood cells in the circulatory transport system.
Nerve cells in the nervous system.
Sperm cells and egg cells in the reproductive systems.
Most differentiation occurs as an organism
develops - lots of stem cells are found in early human embryos.
However, these same stem cells are only found in
small numbers in most adult tissues, such as bone marrow or fat and
compared with embryonic stem cells, adult stem cells have a much
more limited ability to differentiate giving rise to various cells
of the body.
Some typical learning objectives for
this section on stem cells, cell differentiation & specialisation
Be able to
describe how human specialised cells are adapted to their function, including:
(a) sperm cells – acrosome, haploid nucleus
and mitochondria and
(b) egg cells – nutrients in the cytoplasm, haploid nucleus and
changes in the cell membrane after fertilisation,
(c) ciliated epithelial cells for
moving mucous along.
(d) white and red blood cells
systems, menstrual cycle,
Cell division - mitosis, meiosis, sexual/asexual reproduction
Summary of learning objectives and key words or phrases
Be able to describe the idea and need for the specialisation
of cells and stem cells that can differentiate in an embryo to become
various types of specialised cells.
Know that in a developed organism the principal source of
stem cells is in bone marrow.
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