Page 13 - Biology_F5

Biology for Advanced Level Secondary Schools

Cell wall
Plasma membrane Capsule
Cytroplasm
Pili

Plasmid
Bacterial flagellum
Ribosomes
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Nucleoid (circular DNA)

Figure 1.3: Structure of the rod shaped bacterium

Functions of parts of prokaryotic cells (f) The mesosomes which are infoldings
(a) The cell wall of prokaryotic cells of the cell surface membrane act as
provides structural and protective sites for respiratory enzymes.
functions. In some prokaryotes, the (g) Granules of food stores are used as
cell wall is surrounded by a thin sheath, respiratory substrates.
while in others, it is surrounded by a
slim capsule. 1.3.2 Eukaryotic cells
(b) The cytoplasm of prokaryotes is The term Eukaryote comes from two
surrounded by a single cell membrane, Greek words eu meaning 'true' and
and all metabolic processes such as karyon meaning 'nucleus'. Eukaryotic
protein synthesis, respiration, and cells are those cells whose nuclei are
replication take place within the bounded by nuclear membranes. Cells are
typically composed of plasma membrane,
cytoplasm. cytoplasm, nucleus, and organelles such

(c) Genetic material in the form of a single as mitochondria, endoplasmic reticulum,
circular DNA located in the specified ribosomes, and Golgi apparatus. The
region within the cytoplasm controls examples of eukaryotic cells are plant and
animal cells. These cells are characterised
hereditary functions of the cell. by the following features:

(d) The flagellum found in most aquatic (a) They are relatively large in size, ranging
and soil bacteria aids in movement from microscopic to macroscopic.
by a unique process of spinning on an (b) They have true or well organised
axis like a propeller. nuclei with nuclear membranes.
(e) The pili, a structure located on the (c) They have large and numerous
cell wall helps bacteria to increase ribosomes with the sedimentation
the chances of survival by undergoing speed of 80s (The 's' stand for the
conjugation or by enabling anchorage name Svedberg, but is also a unit of
to its host or substrate. measurement).

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