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Biology for Advanced Level Secondary Schools
Intermediate filaments centrioles in the cytoplasm which usually
These are structures found between lie at right angles to each other close to
microtubules and microfilaments. the nuclear membrane. In cross section,
They provide shapes of cells and act each centriole is seen to contain nine
as intercellular tendons that prevent groups of microtubules with three tubules
excessive stretching of the cells. in each group (Figure 1.18). During cell
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division, the centrioles divide and migrate
Centrioles chromosome in opposite poles of the
A centriole is a cylindrical organelle cell where they act as a focus for spindle
found in animal cells, algal cells and formation. Centrioles also produce the
fungal cells, but not in cells of higher basal bodies from which cilia and flagella
plants. Animal cells contain a pair of develop.
(a) (b)
Figure 1.18: Structure of a centriole (a) side view and (b) cross section
Comparison of prokaryotic and
Exercise 1.9 eukaryotic cells
Common features which can be found in
1. What do you understand by the prokaryotic and eukaryotic cells are as
term cytoskeleton? follows:
(a) Both have cell membranes that
2. Explain the functions of microtu- separate the cell’s interior from its
bules and microfilaments in plant surrounding environment.
and animal cells. (b) Both have a cytoplasm that consists
of a jelly-like region within the cell in
3. Describe the structure, location and which other cellular components are
functions of centrioles in animal suspended.
cell. (c) Both have ribosomal particles that
synthesise proteins, and genetic
material of the cell.
The prokaryotic and eukaryotic cells also
differ in many aspects as elaborated in
Table 1.1.
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