Valleys are one of the most common landforms on the surface of the planet. They are carved by flowing water or flowing ice through the process of erosion, which is the gradual wearing away of Earth surfaces through the action of wind and water.
The cellular respiration processes of all living cells make use of the coenzyme Nicotinamide adenine dinucleotide (NAD). It plays a key role in energy metabolism by accepting and donating electrons.
Mitochondria play a central role in cellular metabolism. Metabolic pathways that occur within mitochondria include the TCA cycle, oxidative phosphorylation, amino acid metabolism, and biosynthesis of lipids, heme, and iron-sulfur clusters (Rutter and Hughes, 2015).