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:::Index> The Secret Garden of Genetics>Knowledge Acquisition>Origin of Life>The Basic Unit of
Organism
The Basic Unit of Organism
【Cell Function】
Cells are usually very small and are made up of various shapes and different functions,
e.g. the epidermal cells in the skin are flat and arranged compactly; erythrocytes are
biconcave shaped and capable of transporting oxygen; nerve cells have many spikes
and are able to transmitting signals.
【Cell Structure】
Cells are the most basic units to constitute an organism and classified into many
categories, but are basically made up of a cell membrane, a cytoplasm and a nucleus.
In addition, there exist some different characteristics between animal cells and plant
cells, i.e. plant cells have vacuoles, cell walls and chloroplasts, and animal cells have
lysosomes and centrioles.
Fig.1：The main components of the animal cell
Nucleus：If we compare fruits of peaches and plums to cells, the location of nucleus is
the same as that of the kernels in peaches and plums. A nucleus has a cell blueprint
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and is made up of chromosomes and DNA molecules. A cell must set up its shape
and control activities via the blueprint.
Cell membrane：It constitutes the outer layer of cells and is one kind of lipids in
essence. The cell membrane can control the cell substance tranportation.
Cytoplasm：It is made up of a colloidal matrix. The cytoplasm is diffused between the
nucleus and the cell membrane and contains many organelles.
Mitochondrion：It is made up of a bi-layer membrane; the outer membrane is smooth
and the inner membrane protrudes inwards to form many infoldings. These infoldings
are involved in cell respiration and act as a generator to produce ATP(energy) for
cell operation.
Endoplasmic reticulum：They are classified into rough and smooth endoplasmic
reticulum. The rough endoplasmic reticulum is like an industrial conveyor belt which
can transport substance; the smooth endoplasmic reticulum can produce steroid
hormones.
Golgi body：They are adjacent to the nucleus and formed by the stack of many flat sac
membranes, acting as an industrial cutting device which can modify produced
proteins and make them function.
Cell wall：It encloses the outside of the cell membrane and is made up of cellulose
which can protect cells and maintain their shapes.
Chloroplast ：It is made up of bi-layer membranes and involved in photosynthesis,
acting as a solar cell which can absorb sunlight and generate energy.
Vacuole：It is located at the centre of plant cells. The vacuole can store water and
produce turgor pressure to maintain the cell shape.
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Reviewed by：Zhang, Yong-Ta professor
All rights reserved by National Taiwan Science Education Center