mitochondria

Typical plant and animal cell. Plant and animal cells share many structures, such as ribosomes, mitochondria, and chromosomes, but they also have notable differences: plant cells have chloroplasts, a large vacuole, and a cellulose cell wall. Animal cells do not have a rigid cell wall but have an outside cell membrane only.

A cross-section of a mitochondrion (above) and a 3-D cutaway. Mitochondria have an outer membrane and an inner membrane. The inner membrane is much folded to form christae. Mitochondria have their own DNA and ribosomes.

Membrane-enclosed organelles within eukaryotic cells, containing enzymes responsible for energy production during aerobic respiration. They are found in both plant and animal cells. Mitochondria absorb oxygen (O₂) and complete the breakdown of glucose to carbon dioxide (CO₂) and water (H₂O) to produce energy in the form of ATP, which is used in life processes in the cell. These rodlike or spherical bodies are thought to be derived from free-living bacteria that, at a very early stage in the history of life, invaded larger cells and took up a symbiotic way of life inside them. Each still contains its own small loop of DNA called mitochondrial DNA, and new mitochondria arise by division of existing ones. Mitochondria each have 37 genes.

Mutations in mitochondrial genes are always inherited from the mother. These mutations have been linked to a number of disorders, mainly degenerative, including Alzheimer's disease and diabetes.