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Plant
Cell
Making
a 3D Plant Cell
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Short
and brief description of a plant cell
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Plant
cells contain a variety of membrane-bound structures called organelles.
These include a nucleus that carries genetic material; mitochondria that
generate energy; ribosomes that manufacture proteins; smooth endoplasmic
reticulum that manufactures lipids used for making membranes and storing
energy; and a thin lipid membrane that surrounds the cell. Plant cells
also contain chloroplasts that capture energy from sunlight and a single
fluid-filled vacuole that stores compounds and helps in plant growth.
Plant cells are surrounded by a rigid cell wall that protects the cell and
maintains its shape.
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Plant Cell Structure
Plants are unique amongst the eukaryotes, organisms whose cells have
membrane-enclosed nuclei and organelles, because they can manufacture their own
food. Chlorophyll, which gives plants their green color, enables them to use
sunlight to convert water and carbon dioxide into sugars and carbohydrates;
chemicals the cell uses for fuel.
Like the fungi, another kingdom of eukaryotes, plant cells have retained the
protective cell wall structure of their prokaryotic ancestors. The basic plant
cell has the basic construction of a typical eukaryote cell, but does not have
centrioles, lysosomes, cilia, or flagella as does the animal cell. Plant cells
do have specialized structures: a rigid cell wall, central vacuole,
plasmodesmata, and chloroplasts.
It is estimated that there are at least 260,000 species of plants in the
world today. They range in size and complexity from small, nonvascular mosses to
giant sequoia trees, the largest living organisms as tall as 330 feet (100
meters). Only a tiny percentage of those species are directly used by people for
food, shelter, fiber, and medicine. Nonetheless, plants are the basis for the
Earth's ecosystem and food web and, without them, complex animal life forms
(such as humans) could never have evolved.
Thought to have evolved from the green algae, plants have been around since
the early Paleozoic era, more than 500 million years ago. The earliest fossil
evidence of land plants dates to the Ordovician Period (505 to 438 million years
ago). By the Carboniferous Period, about 355 million years ago, most of the
Earth was covered by forests of primitive vascular plants, such as lycopods
(scale trees) and gymnosperms (pine trees, ginkgos). Angiosperms, the flowering
plants, didn't develop until the end of the Cretaceous Period, about 65 million
years ago -- just as the dinosaurs became extinct.
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Cell
Wall - Like their prokaryotic ancestors, plant cells have a rigid
wall surrounding the plasma membrane. It is a far more complex structure,
however, and serves a variety of functions, from protecting the cell to
regulating the life cycle of the plant organism.
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Chloroplast
- The most important characteristic of plants is their ability to
photosynthesize, i.e. make their own food by converting light energy into
chemical energy. This process is carried out in specialized organelles
called chloroplasts.
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Endoplasmic
Reticulum - The endoplasmic reticulum is a network of sacs that
manufactures, processes, and transports chemical compounds for use inside
and outside of the cell. It is attached to the double-layered nuclear
envelope, providing a connection between the nucleus and the cytoplasm. In
plants, it also connects between cells via the plasmodesmata.
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Golgi
Apparatus - The Golgi apparatus is the distribution and shipping
department for the cell's chemical products. It modifies proteins and fats
built in the endoplasmic reticulum and prepares them for export as outside
of the cell.
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Microfilaments
- Microfilaments are solid rods made of globular proteins called actin.
These filaments are primarily structural in function and are an important
component of the cytoskeleton.
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Microtubules
- These straight, hollow cylinders, composed of tubulin protein, are found
throughout the cytoplasm of all eukaryotic cells and perform a number of
functions.
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Mitochondria
- Mitochondria are oblong shaped organelles found in the cytoplasm of all
eukaryotic cells. In plant cells, they break down carbohydrate and sugar
molecules to provide energy, particularly when light isn't available for the
chloroplasts to produce energy.
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Nucleus
- The nucleus is a highly specialized organelle that serves as the
information and administrative center of the cell.
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Peroxisomes
- Microbodies are a diverse group of organelles that are found in the
cytoplasm, roughly spherical and bound by a single membrane. There are
several types of microbodies but peroxisomes are the most common.
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Plasmodesmata
- Plasmodesmata are small tubes that connect plant cells to each other,
providing living bridges between cells.
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Plasma
Membrane - All living cells have a plasma membrane that encloses
their contents. In prokaryotes and plants, the membrane is the inner layer
of protection surrounded by a rigid cell wall. These membranes also regulate
the passage of molecules in and out of the cells.
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Ribosomes
- All living cells contain ribosomes, tiny organelles composed of
approximately 60 percent RNA and 40 percent protein. In eukaryotes,
ribosomes are made of four strands of RNA. In prokaryotes, they consist of
three strands of RNA.
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Vacuole
- Each plant cell has a large, single vacuole that stores compounds, helps
in plant growth, and plays an important structural role for the plant.
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