What Are Mitochondria?Mitochondria are the powerhouse of cells as they generate energy for cell functioning. The structure of mitochondria is unique. The mitochondrion is a rod or sausage-shaped structure found in animal and plant cells. It is a small organelle whose size is between 0.5 to 1 micrometre in diameter. Hence, it cannot be seen under a microscope unless stained. Unlike other organelles, it has two layers; inner and outer. Each layer performs different functions. Outer Membrane – It is made of proteins. The membrane allows small protein-like molecules to pass through it. Intermembrane Space – It is the space between outer and inner membranes. Inner Membrane – This membrane is made of phospholipids and does not allow molecules to pass through it. Special transporters (carrier molecules) are required to transport substances. Here, ATP production takes place. Cristae – These are the irregular folds of the inner membrane. They increase the space for chemical reactions to take place by increasing the surface area of the membrane. Matrix – It is fluid within the inner membrane. This fluid has several enzymes required for ATP production. It also contains ribosomes, mitochondrial DNA, inorganic and organic molecules, etc.