ATP (adenosine triphosphate) is the universal currency of energy. It is a small molecule with 3 phosphate groups (P) attached to an adenosine molecule i.e. Adenosine-P-P-P
During respiration, high energy C-C, C-H and C-OH bonds are broken. Lower energy bonds are formed and the difference is released and used to attach a P to Adenosine-P-P (ADP adenosine diphosphate), making ATP. When energy is required at a later time by a cell, it can use the ATP and break a P off the end. This releases the energy needed (30.6kJ for every ATP, ADP + P). The more ATPs used, the more energy is released.
For aerobic respiration to occur, the cell needs to possess mitochondria.
Many of the reactions in the stages of respiration involve oxidation by the removal of electrons or hydrogen atoms (H). These are transferred to electron/hydrogen carriers. Ultimately they are passed to oxygen to form water right at the very last stage of respiration.
Two important electron/hydrogen carriers are NAD (nicotinamide adenine dinucleotide), and FAD (flavin adenine dinucleotide).
1. Glucose is phosphorylated twice to make a 6C sugar phosphate. 2 ATPs are used to supply the P groups. This makes the glucose more reactive and so…
2. The 6C sugar phosphate breaks down to form 2, 3-carbon sugar phosphates, called triose phosphates (TP).
3. Hydrogen is removed from each of the 2 TP molecules. The hydrogens are passed to 2 NADs (the NADs are reduced). 2 ATPs are made directly from the conversion of each TP to pyruvic acid (written shorthand as PA or called pyruvate) as the phosphate groups are removed.