The planet closest to the sun is mercury and this is because the order of the planets in the solar system, starting nearest the sun and working outward is the following: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and then the possible Planet Nine. If you insist on including Pluto, it would come after Neptune on the list.
During the krebs cycle NADH (Nicotinamide adenine dinucleotide) and FADH (<span>Flavin adenine dinucleotide) are made and used in the electron transport chan. Hope this helps!</span>