Page 27 - Biology_F5

Biology for Advanced Level Secondary Schools

(e) It increases the surface area for although it can change from one form to
chemical reactions in the cell to take another depending on the physiological
place. conditions of the cells. The matrix contains
(f) It is involved in the formation of Golgi few small ribosomes (70s), phosphate
bodies. granules, respiratory enzymes (such as
ATP synthase) and small mitochondrial
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Exercise 1.6 DNA which is circular and naked (Figure
1.11).

1. Outline the functions of Mitochondrial DNA
endoplasmic reticulum. Outer membrane
Ribosome
2. Describe the structural differences Matrix
between smooth and rough Phosphate granule
Inter membrane space
endoplasmic reticulum. Inner membrane
Cristae
3. Explain how the RER and SER are
Stalked particles
adapted to their roles. Porins in the outer
membrane
Mitochondrion Figure 1.11: A structure of a mitochondrion
A mitochondrion (plural mitochondria) is
an organelle bound by double membranes Functions of a mitochondrion
and it is found in eukaryotic cells. (a) It is a site for aerobic respiration, hence
Mitochondria have been described as it releases energy in the form of ATP.
‘the powerhouses of the cell’ because (b) It is an intermediate site for synthesis
they generate most of the cell’s chemical of important biomolecules such as
energy originally contained in respiratory chlorophyll, cytochromes, steroids,
substrates. This energy is liberated in the and fatty acids.
form of adenosine triphosphate (ATP). (c) The mitochondrion can store and release

calcium ions when required, hence, it
The structure of the mitochondrion regulates calcium ion concentration in
Each mitochondrion is bounded by two
highly specialised membranes. Thus, it is the cell.
a double membrane organelle. The outer
membrane is quite smooth, it has many Adaptations of a mitochondrion
copies of a transport protein called porins, The mitochondrion is specialised to its
which forms large aqueous channels functions, as follows:
through the lipid bilayer. On the inside is (a) The outer membrane contains lots
the inner membrane separated from the of porins that allow the passage of
outer membrane by a space, measuring molecules for respiration.
6 - 8 nm. The inner membrane is deeply (b) The inner membrane is highly folded
folded into infolding known as cristae, into cristae that increase surface area.
which project into the matrix space. (c) The membranes are permeable to
allow the passage of all diffusable
Generally, the organelle has an oval shape,
materials. This allows raw materials in

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