Anaerobic respiration

In the syllabus and the exam

Anaerobic respiration appears in the respiration content standard alongside aerobic respiration, comparing energy yield, end products and word equations for both humans (glucose to lactic acid) and yeast (glucose to ethanol and carbon dioxide). Exam questions typically give a scenario, such as a sprinter, a root under waterlogged soil, or yeast in dough, and ask candidates to identify which type of respiration occurs and to justify the answer using oxygen availability, energy yield per glucose molecule, and the end products formed. A common confusion is treating anaerobic respiration as respiration with no energy released at all; SPM answers must state that a small amount of energy is still released, just far less than in aerobic respiration, because glucose is only partly broken down. Another slip is naming lactic acid as a product of yeast fermentation instead of ethanol and carbon dioxide.

Example

Muscle cells switch to anaerobic respiration during intense exercise when oxygen supply cannot keep pace with demand, causing lactic acid to build up and cramp to set in.

Related terms

Aerobic respirationATPFermentation

Source:SRC-DSKP-EN