What are the two types of fermentation in mitochondria?
Mitochondria are organelles that play a crucial role in cellular respiration. They are
the powerhouses of the cells and generate ATP through the process of oxidative
phosphorylation. In addition to ATP production, mitochondria also play a role in
calcium regulation, apoptosis, and fatty acid metabolism. Mitochondria contain their
own DNA, which is circular and codes for some of the proteins and RNA molecules
necessary for respiratory chain function. The DNA also makes it possible for
mitochondria to reproduce themselves independently of the cell.
The cristae are inner membrane folds that increase the surface area of the inner
membrane, allowing for more proteins to be embedded in the membrane and,
therefore, increasing electron transport chain efficiency. The cristae also help to
separate the mitochondrial matrix, the fluid portion of the inner membrane that
contains the enzymes responsible for the Krebs cycle, from the intermembrane
space where the electron transport chain occurs. The large surface area of the
cristae provides more area for these reactions to occur, making the mitochondrial
energy production more efficient.
In addition to producing ATP via oxidative phosphorylation, mitochondria can also
perform fermentation. This occurs when the electron transport chain is unable to
function due to a lack of oxygen, as occurs in anaerobic conditions. There are two
types of fermentation in mitochondria; lactic acid fermentation and alcoholic
fermentation. Lactic acid fermentation occurs in mammals and converts pyruvate into
lactate, regenerating NAD+ for glycolysis to continue. Alcoholic fermentation occurs
in plants, fungi and bacteria, converting pyruvate into ethanol and carbon dioxide.
References:
1. Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York:
Garland Science; 2002.
2. Voet D, Voet JG, Pratt CW. Fundamentals of Biochemistry: Life at the Molecular Level.
3rd edition. New York: Wiley; 2008.
3. Lehninger AL, Nelson DL, Cox MM. Principles of Biochemistry. 5th edition. New York:
Freeman; 2008.