Mitochondrion

Mitochondria are found in the cytoplasmic matrix of most cells. The mitochondria move to regions of the cell where they are most required.

Structure

The structure of the mitochondria is completely related to its functioning. A mitochondrion is a small, usually elongated, sac-like structure bounded by a double membrane.The inner membrane has inward directed folds, or ridges, called cristae. The internal space is filled with fluid, the mitochondrial matrix. The central cavity or lumen is filled with fluid containing enzymes, vitamins essential for chemical respiration and accumulations of the energy- rich ATP molecules that are formed as a result of respiration in the mitochondria.

• the mitochondria contain the respiratory enzymes catalyzing the reactions of the Krebs cycle and oxidative phosphorylation, which form the latter stages of cellular respiration;
• mitochondria produces energy packets in the form of ATP molecules and are thus referred to as the "power houses" of cells.

Notice in the above picture of a mitochondria how it looks like there are a number of membrane folds inside the mitochondria.