Plant Cell Composition and Structure
Robert Hooke is usually credited as the one to discover plant cells
in 1665 when he published his findings in Micrographia. What Hooke had
discovered were cellular walls when he was studying dead tissue of the
cork tree. His compound microscope did not allow enough magnification to
see any further into the cells themselves, but his publication of
Micrographia became widely popular and a basis for further study of
cellular discovery.
By 1831 the nucleus of plant cells was discovered by Scottish
botanist, Robert Brown and by 1838 the cell theory was fully developed
by German Scientist Matthias Schleiden, German zoologist, Theodor
Schwann and German biologist Rudolf Virchow who all stated and agreed
that “cells are the basic unit of structure in all living things”.
These men all contributed to the foundation of biology greatly and as
time went on more and more was discovered and learned about the plant
cell composition and structure. Now we have a huge understanding of the
cellular structure of plants.
We know now through the cell theory developed by these men that all
living things are made up of cells. Cells are usually divided into two
categories; eukaryotic and prokaryotic. Eukaryotic cells contain a
nucleus unlike prokaryotic cells which do not have nuclei. Plant cells
are eukaryotic cells that contain many different components which will
be addressed shortly.
The smallest eukaryotic cell is the green algae, Osterococcus tauri
that is only about 0.8 micrometers in size. The average size of a
eukaryotic cell is about 25 micrometers, but this can be a bit
misleading because of the wide array of sizes and shapes of known
eukaryotic cells.
Within a eukaryotic cell is the chromosome containing nucleus,
nucleolus, chloroplast, mitochondrion, ribosomes, smooth endoplasmic
reticulum, rough endoplasmic reticulum, cytoplasm, cytosal, the cellular
wall, and vacuole; all of which contribute to the structure and function
of a typical plant cell.
Cytoplasm
Cytoplasm is the term used to indicate everything within the cellular
walls; organelles and cytosol.
Cytosol
Cytosol is the fluid part of the cell in which the organelles dwell.
Cytosol is usually mostly water but also contains proteins concerned
with the cell’s metabolism.
The Nucleus
The nucleus is the most visible organelle within the cell. An
organelle is defined as “a specialized subunit within a cell that has a
specific function, and is usually separately enclosed within its own
lipid membrane.” This nucleus is encapsulated by a double membrane and
is the ‘brains’ of all cellular activity containing all the DNA
information that makes each cell unique in its structure and function.
The Nucleolus
The nucleolus is located within the nucleus and manufactures
ribosomes which are extremely vital in the process of protein synthesis.
These ribosomes move out of the nucleus and position themselves on the
rough endoplasmic reticulum (rough ER)
Rough Endoplasmic Reticulum
Rough ER shows up bumpy under an electron microscope due to the
presence of attached ribosomes. Rough ER operates as a housing base for
these ribosomes to synthesize proteins so they can be carried throughout
the cell.
Chloroplast
 Chloroplasts
are found in higher functioning plant cells and hold the cell’s
chlorophyll. (Chlorophyll is what gives a plant its green color) A
double outer membrane encases chloroplasts.
Mitochondria
Mitochondria are another type of organelle found within a eukaryotic
cell and supply all the power and energy a plant cell needs to function.
The double membrane of mitochondria is a study of contrasts. The outer
membrane is relatively smooth with a complex folding inner membrane.
These folds within the inner membrane are referred to as cristae and
increase the membranes surface area greatly. The reason for this is
energy production. The cell’s food, in the form of sugar is mixed with
oxygen to produce the primary energy supply; ATP.
Vacuole
 A
vacuole is usually the largest organelle within the plant cell that has
several functions relating to cellular digestion and waste; much like
the intestines of a human body. Another major function of the vacuole is
to provide turgor pressure. It is turgor pressure that makes a plant
rigid and erect. Noticing a drooping house plant is a perfect example of
low turgor pressure. The vacuole holds nutrients, water and waste all of
which increase growth by increasing the cell’s size.
The descriptions above only cover the basic components of plant
cellular structure and function. There is so much more to know about the
cellular structure of plants and is well worth the effort of learning
more. |
