Out of all the organelles there
are two that have fascinated microbiologists for the past hundred years. The
first is the mitochondria, nicknamed the “powerhouse of the cell.” The second
is the chloroplast in plant cells that have functions similar to those of the
mitochondria. What do these organelles do? What are the similarities and differences
of these organelles? This essay will help you to understand these two fascinating
Mitochondria are small cytoplasmic organelles.
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They are five to 10 micrometers long and one to .5 micrometers wide. They main
function is to provide energy for cell activities. They house the respiratory
enzymes that convert oxygen and the products of fat, carbohydrate, and protein
metabolism into adenosine triphosphate (ATP) and guanosine triphosphate (GTP),
chemicals that have high-energy bonds. They are hollow all except for a folded
line of matter that contains the ribonucleic acid (RNA) or deoxyribonucleic
acid (DNA) of the cell.
Mitochondrion make use of a process known as oxidation
to make fat acids and pyruvate acid into (indirectly) ATP and Pi (inorganic
phosphate). The process goes as follows:
1) Oxidation of pyruvate acid
into acetyl coenzyme A.
2) Oxidation of fat acids into acetyl coenzyme A.
of acetyl coenzymes from step one and two into CO2 and NADH2.
of NADH2 by oxygen forming water.
5) Synthesis of ATP coupled to NADH2 oxidation
by process of oxidative phosphorylation.
Most of this is self explanatory
except for the last step (5). The final step contains a phrase “coupled to.”
This means that the compound (NADH2) must be present and have been oxidized
for the synthesis of ATP, similar to a catalyst’s presence of some reactions.
the mitochondrion’s major purpose is to supply the cell with the much needed
ATP, it has others. Included in this list are nitrogen metabolism, porphyrin
synthesis and steroid hormone synthesis.
are complicated green organelles that occur within the cytoplasm of plant cells.
They are the main sites of photosynthesis. Photosynthesis is the change of
light energy, CO2 water into sugar which is used as food. They are disk shaped
organelles and are surrounded by two layers of membrane that enclose the watery
inside or stroma. Inside the stroma there are green dots called grana (grains)
that hold chlorophyll.
As with the mitochondrion the Chloroplasts use radiant
or solar energy to make a product. In this case hexose.
1) The pigment complexes
in the chloroplasts (including but not limited to chlorophyll) collect solar
2) The light energy gathered in the first step is used to run an electron
transport chain that oxidizes water into 0xygen. NADP is reduced.
synthesis is coupled to the electron transport train.
4) Carbon dioxide is
fixed and converted to hexose. This process requires ATP and the reduced NADP
created in step three and two respectively.
mitochondria and the chloroplasts have complex purposes in the cell. This first
as the powerhouse that creates energy for cell activities. The second, chloroplasts
which produce food that is used to power the cell. These procedures are facinating
and more could be learned if time would allow it.
Genes and Organelles. Sager, Ruth. 1972. London.
Genetics and Biogenesis
of Chloroplasts and Mitochondria. Bucher, Th. . 1976. Amsterdan.
Chloroplasts and Bacterial Membranes. Prebble, J N. 1981. New York.
in Enzymology. Volume 207. Rudy Benardo. 1992. San Diego.