The mitochondrion (plural, mitochondria) is a type of
organelle that specializes in making ATP (molecule used by cells as
main energy source). They have various enzymes to catalyze cellular
respiration. Bacteria have no mitochondria; they make ATP in their cell
walls and cytoplasm. Cells that have a very high demand for energy tend
to have many mitochondria e.g. liver needs more because needs more
energy. Mitochondria, like most organelles, can move within the cell and
they grow and divide independently. Each has two membranes, one highly
folded inside the other. Double-membrane system: Smooth outer membrane
(lipid bilayer) faces cytoplasm and permeable to small solutes; blocks
macromolecules where as Inner Membrane (cristae) folds back on itself to
enlarge surface area for chemical reactions to take place. Membranes
form two distinct compartments. ATP-making machinery is embedded in the
inner mitochondrial membrane.
- Mitochondria and chloroplasts have similarities with bacteria,
- Enveloped by a double membrane
- Contain free ribosomes and circular DNA molecules
- Grow and reproduce somewhat independently in cells
They may have evolved from ancient bacteria that were engulfed but not
digested. Mitochondria and chloroplasts developed because as a
prokaryote it gained protection by living inside the eukaryote and in
turn produced energy for the eukaryote (symbiotic relationship).
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