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.
1 Explain the important role of ATP in cell metabolism. 2  Describe the relationship between photosynthesis and cellular respiration in photosynthetic organisms. 3  Explain why many biological macromolecules such as ATP and lipids contain high energy bonds.  Explain the importance of enzymes as catalysts in cell reactions.