Plant Chlorophyll and Chloroplast
Chlorophyll is found within the chloroplast of a eukaryotic plant
cell. Without chlorophyll and the chloroplasts that house them,
photosynthesis would not occur and plants would not grow.
Chloroplasts are organelles within the cellular structure of plant
cells. An organelle can be defined as “a specialized subunit within a
cell that has a specific function, and is usually separately enclosed
within its own lipid membrane.” Plant cells are made up of many
different types of specific organelles, but chloroplasts are the
organelles directly responsible for the action of photosynthesis and
contain very specific parts that conduct photosynthesis.
The outer membrane of a chloroplast is very permeable with the inner
membrane becoming more selective and houses carriers of sugars and
certain types of proteins that are needed only within the chloroplast.
Then there is a type of membrane known as the thylakoid membrane that is
composed of stacks of thylakoids known as granum.
Thylakoids are a type of sub-organelles where the actual process of
photosynthesis occurs. They are a flat disc shape and are stacked on top
of each other into columns called granum. There is some space between
each disc called lumen, but photosynthesis only occurs in the outermost
layer of thylakoids; the ones closest to the cellular wall. Within the
thylakoid membrane the pigments responsible for capturing sunlight,
chlorophyll and carotenoids, can be found. This complex formation
manages to increase the surface area to allow a greater amount of light
to be captured for photosynthesis. Here is an illustration of thylakoids
and granum.
The thylakoids handle the conversion of the kinetic energy of the sun
into a usable chemical energy source for the plant cell, but the stroma
lamellae is where the conversion of carbon dioxide into sugars actually
occurs.
The chloroplasts house the essential pigment chlorophyll. Chlorophyll
is what takes in the sunlight (absorbs) and begins the transformation
process into usable energy. This pigment is housed in the thylakoid
membranes and looks like this.
In order to understand chlorophyll more thoroughly it is necessary to
understand what a pigment is. Pigment is a substance that absorbs light
and it is light absorption that becomes a little tricky to understand.
Each type of pigment will absorb a predetermined amout of light and
reflect the rest of the light wavelengths back into the atmosphere.
Chlorophyll assimilates all visible wavelengths of light except green.
It bounces green off of its surface, and that is the color we see. See?
It isn’t too difficult to understand. Present in photosynthesizing
plants, there are several pigments: Carotene, Xanthophyll, Phaeophytin
a, Phaeophytin b, Chlorophyll a and Chlorophyll b. Carotene is an orange
pigment, Xanthophyll a yellow, Phaeophytin a is a gray/brown pigment,
Phaeophytin b a yellow/brown, Chlorophyll a is a blue/green and
Chlorophyll b is a yellow/green pigment. Of all of these, Chlorophyll is
the most common of them all. Between all of these pigments, there is a
wide array of the color spectrum that can be collected by the plant
itself except in the yellow/green spectrum which accounts for all of the
lush green we see in nature.
Once the basics are understood of chlorophyll and chloroplasts, it
becomes easier and easier to understand the process of photosynthesis. |
