Some knowledge
of cell structure is usually required for introductory courses in Human Anatomy and Physiology (e.g. ITEC), Human Biology (e.g. A-Level) and other first-level courses in health sciences and related subjects.
The structure of cells varies according to the type
and purpose of the cell (for example, which functions it is performing
and in which part of the body).
All cells contain organelles.
These are structures within the cell that are specialised for particular
functions.
The following diagram illustrates a single cell and
simple representations of key organelles:
It is also important to know something about each
of these organelles:
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Organelle
|
Structure/Function
|
|
|
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Cell Membrane
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The cell membrane keeps the cell together
by containing the organelles within it. Cell membranes are
selectively-permeable, allowing materials to move both into
and outside of the cell.
|
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Centrosomes
|
The centrosomes contain the centrioles,
which are responsible for cell-division.
|
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Cytoplasm
|
Cytoplasm is a jelly-like substance that
is sometimes described as "the cell-matrix". It
holds the organelles in place within the cell.
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Golgi Apparatus
|
The golgi apparatus of a cell is usually connected
to an endoplasmic reticulum (ER) because it stores
and then transports the proteins produced in the ER.
|
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Lysosomes
|
Lysosomes are tiny sacs filled with enzymes
that enable the cell to utilize its nutrients. Lysosomes also
destroy the cell after it has died, though there are some
circumstances (diseases/conditions) in which lysosomes begin
to 'break-down' living cells.
|
|
Microvilli
|
"Microvilli" is the pural form;
"Microvillus" is the singular form.
Microvilli are finger-like projections on the
outer-surface of the cell.
Not all cells have microvilli.
Their function is to increase the surface area of the cell,
which is the area through which diffusion of materials both
into, and out of, the cell is possible.
|
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Mitochondria
|
"Mitochondria" is a plural term;
which is appropriate as these are not found alone.
The quantity of mitochondria within cells varies
with the type of cell.
These are the energy producers within the cell. They generate
energy in the form of Adenosine Tri-Phosphate (ATP). Generally,
the more energy a cell needs, the more mitochondria it contains.
|
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Nuclear Membrane
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The nuclear membrane separates the nucleus
and the nucleolus from the rest of the contents of the cell.
|
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Nuclear Pore
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Nuclear pores permit substances (such as
nutrients, waste, and cellular information) to pass both into,
and out of, the nucleus.
|
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Nucleolus
|
The nucleolus is responsible for the cell
organelles (e.g. lysosomes, ribosomes, etc.).
|
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Nucleus
|
The nucleus is the "Control Center"
of the cell, which contains DNA (genetic information)
in the form of genes, and also information for
the formation of proteins.
Information is carried on chromosomes, which are a form of
DNA.
|
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Ribosomes
|
Ribosomes interpret cellular information
from the nucleus and so synthesize appropriate proteins, as
required.
|
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Rough Endoplasmic Reticulum (RER)
|
"Rough" indicates that there are
ribosomes attached to the surfaces of the endoplasmic
reticulum. The endoplasmic reticulum is where proteins
and lipids are produced within the cell, and is also concerned
with the transport of these materials within the cell.
|
|
Smooth Endoplasmic Reticulum (SER)
|
"Smooth" indicates that there are
no ribosomes attached to the surfaces of the endoplasmic
reticulum.The endoplasmic reticulum is where proteins
and lipids are produced within the cell, and is also concerned
with the transport of these materials within the cell.
|
A simple representation of the structure of animal cell membranes
is shown below.
