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.
These preformed components then pass through a salvage pathway that recycles them back into the active form. Some NAD is also converted into nicotinamide adenine dinucleotide phosphate (NADP); the chemistry of this related coenzyme is similar to that of NAD, but it has different roles in metabolism.icotinamide adenine dinucleotide, like all dinucleotide s, consists of two nucleotides joined by a pair of bridging phosphate groups. The nucleotides consist of ribose rings, one with adenine attached to the first carbon atom (the 1' position) and the other with nicotinamide at this position.