Mitochondria (singular: mitochondrion) are the sites of aerobic respiration, where most of a cell's ATP is made. They are usually rod-shaped or oval, about 1 µm wide and 1 to 10 µm long.
• Double membrane (envelope): the outer membrane is smooth; the inner membrane is folded into cristae.
• The cristae give a large surface area for the proteins of the electron transport chain and the enzyme ATP synthase, which make ATP (oxidative phosphorylation).
• The matrix is the fluid inside the inner membrane. It contains the enzymes of the link reaction and Krebs cycle.
• The matrix also contains circular DNA and 70S ribosomes, so a mitochondrion can make some of its own proteins and can divide to make more mitochondria.
• The space between the two membranes is the intermembrane space.Mitochondria and cell activity
Cells with a high demand for energy have many mitochondria, often with many densely packed cristae. Examples include muscle cells (for contraction), the midpiece of sperm (for swimming), liver cells, and cells lining kidney tubules and the small intestine that carry out active transport. In an electron micrograph, the number of mitochondria and the density of their cristae tell you how metabolically active a cell is.The circular DNA and 70S ribosomes, similar to those of bacteria, are evidence that mitochondria evolved from bacteria that once lived inside other cells (the endosymbiotic theory).
• Double membrane (envelope): the outer membrane is smooth; the inner membrane is folded into cristae.
• The cristae give a large surface area for the proteins of the electron transport chain and the enzyme ATP synthase, which make ATP (oxidative phosphorylation).
• The matrix is the fluid inside the inner membrane. It contains the enzymes of the link reaction and Krebs cycle.
• The matrix also contains circular DNA and 70S ribosomes, so a mitochondrion can make some of its own proteins and can divide to make more mitochondria.
• The space between the two membranes is the intermembrane space.Mitochondria and cell activity
Cells with a high demand for energy have many mitochondria, often with many densely packed cristae. Examples include muscle cells (for contraction), the midpiece of sperm (for swimming), liver cells, and cells lining kidney tubules and the small intestine that carry out active transport. In an electron micrograph, the number of mitochondria and the density of their cristae tell you how metabolically active a cell is.The circular DNA and 70S ribosomes, similar to those of bacteria, are evidence that mitochondria evolved from bacteria that once lived inside other cells (the endosymbiotic theory).