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.
In addition coenzyme A is involved with acetylation reactions. These reactions are important in proper protein function and as a result many of the proteins in the body have undergone such modification reactions in which an acetate group is added to the protein.