Question

What is the end-product of anaerobic respiration in animals?

Answer 1

Hint: Anaerobic respiration occurs in the absence of oxygen and the end product of such a reaction is an organic acid that gets accumulated in muscles during heavy exercises. This product is mainly responsible for the cramps experienced after exercise.

Complete answer:
Animals like all other organisms need energy to carry out the various biochemical and biophysical processes inside their body. The food consumed by animals acts as the source of energy needed by them, and the oxygen that they breathe helps in breaking down the complex molecules present in food into simpler molecules and the energy released is stored for future use. This metabolic process of oxidizing simpler food molecules to release energy is known as respiration.
Normally respiration is carried out in an abundance of oxygen that acts on glucose molecules to give carbon dioxide, water and sufficient amounts of energy. This is known as aerobic respiration.
$$C_6{H}_{12}{O}_6+6O_2\stackrel{\text{anaerobic respiration }}{\to }6C{O}_6+6H_{2}O+38ATP$$
But many times oxygen is not completely accessible to the cells that are in an urgent need of energy and the glucose molecules get broken down in the absence of oxygen. This type of respiration is called anaerobic respiration. The glucose molecule undergoes a partial breakdown to give lactic acid as the final product. Lactic acid causes cramps after heavy exercise.
$$C_6{H}_{12}{O}_6\stackrel{\text{anaerobic respiration }}{\to }2C_3{H}_6{O}_3+2ATP$$
The $$ATP$$ molecules released in respiration are a measure of the amount of energy released in the process. Therefore, anaerobic respiration releases a limited amount of energy as compared to the aerobic respiration process.
Hence, the end product of anaerobic respiration is lactic acid $$(C_3{H}_6{O}_3)$$.

Note:
The process of respiration is a complex process in animals that involves the use of multiple organs and a complete respiratory tract. Respiration should not be confused with breathing, as inhaling and exhaling air is one small part of the respiration process and not the process itself.