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.
This molecule acts as a shuttle for electrons during cellular respiration. At various chemical reactions, the NAD+ picks up an electron from glucose, at which point it becomes NADH. Then NADH, along with another molecule flavin adenine dinucleotide (FADH2), will ultimately transport the electrons to the mitochondria, where the cell can harvest energy stored in the electrons.Thus it plays a key role in energy metabolism by accepting and donating electrons.