Aerobic respiration

In the syllabus and the exam

Aerobic respiration is the pathway examined in most depth within the respiration chapter, and candidates must be able to write its full word equation (glucose plus oxygen yields carbon dioxide, water and a relatively large amount of energy), identify that it takes place mainly in the mitochondria, and explain why it releases far more energy per glucose molecule than the anaerobic alternative, because glucose is broken down completely in the presence of oxygen rather than only partially. A frequent exam angle links aerobic respiration to the structure of the mitochondrion, asking candidates to explain why cells with high energy demands, such as muscle cells or sperm cells, contain unusually large numbers of mitochondria with extensively folded inner membranes, connecting this term back to organelle structure covered in earlier chapters. A common error is writing an incomplete or unbalanced word equation, particularly omitting water as a product or reversing reactants and products, and mixing up aerobic respiration's products (carbon dioxide and water) with anaerobic respiration's very different products in humans (lactic acid, with no carbon dioxide released). Candidates should also be able to distinguish aerobic respiration clearly from breathing and from cellular respiration as the broader umbrella term, since these three related but distinct terms are frequently tested together in short-answer questions designed to catch imprecise vocabulary. Candidates should also be able to state the approximate proportion of energy in glucose that aerobic respiration releases compared with anaerobic respiration in humans, since this contrast is what explains why sustained, oxygen-rich exercise is more energy-efficient than very short, intense bursts of activity.

Example

During a slow jog, muscle cells rely mainly on aerobic respiration, using the oxygen delivered by the blood to fully break down glucose into carbon dioxide and water.

Related terms

Cellular respirationAnaerobic respiration

Source:SRC-DSKP-EN