Energy Acquistion
from Campbell's
Biology, Benjamin/Cummings Publishing Co., 1990
Energy Transducers:
Mitochnodria and Chloroplasts
-
As open systems, cells obtain their energy from their surroundings.
Eurocratic cells accomplish this with mitocondria and chloroplasts, two
organelles that act as energy transducers.
-
Both mitocondria and chloroplasts are enclosed in membranes, but they are
not considered part of the endomembrane system. Their membrane proteins
are not made by the ER, but the free ribosomes and by ribosomes contained
within the mitocondria or chloroplasts. These organelles also contain
a small amount of DNA that programs the synthesis of some of their proteins.
-
Mitocondria are sites of cellular respiration in the eukayotic cells, capable
of using oxygen to convert the chemical energy of sugars, fats, and other
molecular fules into the the "High-energy" phosphate bonds of ATP.
-
Mitocondria are compartmentalized by an outer-smooth membrane and an inner
membrane folded into convolutions called cristae. Many of the metabolic
reactions of respiration take place in the space enclosed by the inner
membrane called the mitocondrial matrix. Enzymes built into the inner
membrane also function in respiration.
-
Chloroplasts, a specialized type of a group of plant organelles callec
plastids, contain chlorophyll and other pigments, which function in photosynthesis.
Chloroplasts are enclosed by two membranes surrounding the fluid stroma
in which are embedded the thylakoids. These flattened sacs may be
stacked to form grana.