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Mitochondria - Turning on the Powerhouse
Mitochondria are known as the powerhouses of the cell. They are organelles
that act like a digestive system that takes in nutrients, breaks them down, and
creates energy for the cell. The process of creating cell energy is known as
cellular respiration. Most of the chemical reactions involved in cellular
respiration happen in the mitochondria. A mitochondrion is shaped perfectly to
maximize its efforts.
Mitochondria are very small organelles. You might find cells with several
thousand mitochondria. The number depends on what the cell needs to do. If the
purpose of the cell is to transmit nerve impulses, there will be fewer mitochondria
than in a muscle cell that needs loads of energy. If the cell feels it is not getting
enough energy to survive, more mitochondria can be created. Sometimes they
can even grow, move, and combine with other mitochondria, depending on the
cell's needs.
Mitochondria Structure
Mitochondria have two membranes (not one as in other organelles). The outer
membrane covers the organelle and contains it. The inner membrane folds over
many times (cristae). That folding increases the surface area inside the
organelle. Many of the chemical reactions happen on the inner membrane of the
mitochondria. The increased surface area allows the small organelle to do as
much work as possible. If you have more room to work, you can get more work
done. Similar surface area strategies are used by microvilli in your intestinal cells.
The fluid inside of the mitochondria is called the matrix.
Using Oxygen to Release Energy
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How are mitochondria used in cellular respiration? The matrix is filled with water
(H2O) and proteins (enzymes). Those proteins take food molecules and combine
them with oxygen (O2). The mitochondria are the only place in the cell where
oxygen can be combined with the food molecules. After the oxygen is added, the
material can be digested. They are working organelles that keep the cell full of
energy.
A mitochondrion may also be involved in controlling the concentration of calcium
(Ca) within the cell.