There are two types of electron carriers that are particularly important in cellular respiration: NAD +start superscript, plus, end superscript (nicotinamide adenine dinucleotide, shown below) and FAD (flavin adenine dinucleotide). Chemical structures of NAD+ and NADH.
Phosphorylation: Energy released from the breakdown of glucose is used to phosphorylate ADP to make ATP. A net total of four ATP molecules are produced directly via substrate level phosphorylation. The remaining ATP is produced indirectly via the electron transport chain (oxidative phosphorylation)