Plant Cells and Photosynthesis
Most of us have at least heard the word photosynthesis, but I would
bet that most of us couldn’t even describe even one aspect of this
amazing procedure correctly. In order to understand plants, a basic
fundamental understanding of photosynthesis is a must. The following is
a basic, but thorough explanation of rarely understood process.
The word photosynthesis can be broken down into two words; ‘Photo’
which developed from the Greek word ‘phos’ that means ‘light’ and
synthesis which is another Greek derived word meaning ‘put together’.
Plants put the kinetic energy of light together with air and water
molecules to produce the chemical energy of carbohydrates as food for
themselves. Confusing? It is a bit, but taking this process one step at
a time makes it far easier to understand.
Within the cellular structure of a plant cell, you will find self
contained units called
 chloroplasts
within the cellular wall. Chloroplasts are responsible for manufacturing
chlorophyll and chlorophyll is a pigment that gives a plant its green
color. Chlorophyll is also responsible for assisting the photosynthetic
process by interacting with sunlight in order to convert water and
carbon dioxide into a useable form of energy; glucose. It takes six
water molecules plus six carbon dioxide molecules to equal one molecule
of glucose that will be accompanied by six oxygen molecules. The
following diagram is for those who would like to see that is a more
scientific language.
6H2O + 6CO2= C6H12O6+ 6O2
Why does a plant need to convert water and carbon dioxide into
carbohydrates? Neither carbon dioxide nor water can store a decent
amount of the glucose energy that a plant needs, but if that plant
converts it into the sugar rich substance of carbohydrates, then it can
thrive and continue to grow through the second phase of this process
known as respiration. Respiration is when, on a cellular level, a plant
begins to break down the stored carbohydrates, providing itself with the
fuel it needs for growth and metabolism.
Most of us are aware that plants and trees provide us with much
needed oxygen, but how many of us know why? How does that work exactly?
The answer lies in the above chemical equation. Remember it takes six
water molecules plus six carbon dioxide molecules to equal one molecule
of glucose (carbohydrate) that will be accompanied by six oxygen
molecules? Those six oxygen molecules are released through the leaves of
the plant and into the atmosphere while the plant keeps the glucose
molecule for food. This is a pretty efficient system that benefits both
the plant and the environment as a whole.
Most of the process of photosynthesis occurs within the leaves of the
plant itself, and remember that most of photosynthesis occurs within the
chloroplasts which look like this.
The carbon dioxide, water and sunlight needed to complete the process
have to be obtained by the plant through the leaf. Carbon dioxide is
taken into the plant through tiny holes called stomata. When the plant
releases its excess oxygen, it is released through the stomata as well.
A plant takes in water through the roots and delivered to the leaves,
and sunlight is absorbed into the leaf through the chloroplasts
mentioned earlier.
Outer and inner membranes: encase this organelle and protect
it.
Stroma Lamellae: This is where carbon dioxide is actually
converted to sugar. Stroma lamellae are a thick and dense fluid.
Thylakoid: This is where the kinetic energy of the sun is
transformed into a more usable chemical energy.
Granum: Granum are stacks of thylakoids.
The more difficult aspect of photosynthesis to understand is the two
stages it goes through known as the light and dark reactions. Light
reactions can only occur in the presence of sunlight and dark reactions
do not need the sun but mostly occur during the daylight.
Light reactions happen in the thylakoid stacks and are the place
where sunlight is directly converted into ATP and NADPH. These two forms
of energy are what a plant will use in the dark reaction process to
manufacture its food in the form of sugar rich carbohydrates. Dark
reactions are where carbon dioxide converts to sugar with the help of
ATP and NADPH in the stroma. Once the conversions take place, the plant
has made food for itself and released much needed oxygen into the
atmosphere. |
