Page 39 - Biology_F5

Biology for Advanced Level Secondary Schools

1.3.3 Cell differentiation Significance of cell differentiation
Cellular differentiation is the process Cell differentiation has the following
of cell transformation from one form to significance:
another. It leads to the development of (a) It modifies cells to suit their functions
specialised types of cells for carrying out more efficiently. This means that,
specific functions. This process involves during differentiation the cell becomes
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biochemical and structural changes. equipped with structural and/or
The differentiated cells become more chemical changes to enhance its
specialised than the undifferentiated ones.
efficiency.
In most cases, differentiation occurs For examples:
during the development of a multicellular (i) Spermatozoa are packed with
organism, as it changes from a simple numerous mitochondria and
zygote to a complex system of cell types acrosomal enzymes. They also have
or tissues. The process continues to flagella. All these features facilitate
adulthood; as adult stem cells divide and efficient fertilisation of egg cells.
create fully differentiated daughter cells (ii) Female gametes (egg cells) have
during tissue repair. Differentiated cells
change in size, shape, membrane potential, numerous microvilli for absorption
metabolic activity, and responsiveness of food from follicular cells. They
to signals. Cell differentiation leads to also have a large proportion of
cell specialisation, which in turn leads cytoplasm which contains food
to division of labour that improves the reserve for the developing embryo.
efficiency of the organisms. Examples of (iii) Nerve cells have features like
specialised cells in animals are sex cells, myelin sheath and nodes of Ranvier,
nerve cells, red blood cells, and epithelial which facilitate rapid transmission
cells. In plants the examples of specialised of impulses. The synaptic vesicles
cells include: xylem, phloem, root hair, contain neurotransmitters that aid in
and parenchyma cells. Figure 1.19 shows synaptic transmission of impulses.
root hair cell, as an example of specialised (iv) The cells in xylem vessels and
plant cell. tracheids are hollow, and have
lignified cell walls for efficient
Cell wall
carriage of water and dissolved
mineral salts.
(b) It enables cellular organisation, as a
Cytoplasm way of forming different tissues and
organs (organogenesis) through the
Vacuole expression of a specific set of genes
within the body to perform more
specialised and complex tasks.
Nucleus (c) It forms the basis for embryonic stem
cell research, whereby researchers
can identify stem cells, which can
Figure 1.19: Root hair cell
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