Respiration is one of the most important chemical processes, which is carried out by all living organisms including plants, animals and humans in order to release the energy required for life processes. Cellular respiration is the metabolic process of cells which involves the breakdown of the nutrient molecule to generate energy. Basically, respiration is the process where the energy stored in fuel is converted into the form where it could be used. They are controlled by enzymes. Typically, the energy stored in the molecular bonds of sugar or fat molecules is used to make ATP. ATP (Adenosine Triphosphate) is the energy currency for the cells. More simply, ATP is the primary energy carrier in living things. The chemical formula of ATP is C10H16N5O13P3 and mitochondria is the part of the cell where it manufactures ATPs from the respiration. The complete balanced chemical formula of respiration is C6H12O6 + 6O2 → 6CO2 + 6H2O. It occurs both during the presence or in the absence of oxygen, and aerobic respiration and anaerobic respiration are two kinds of cellular respiration.

ATP structure + function

The word ‘aerobic’ means the presence of oxygen. By knowing the definition of the term, we can guess pretty easily about what aerobic respiration means. Aerobic respiration is the respiration that requires oxygens in order to produce energy. Aerobic respiration is known to be more efficient than the anaerobic respiration since it produces the ATP way quicker, which also could mean that it requires more oxygen than anaerobic respiration. Aerobic respiration could create oxygens more easily because oxygen is an excellent electron acceptor for the chemical reactions involved in generating ATP. The chemical equation for aerobic respiration is known as C6H12O6 + 6O2  → 6CO2  + 6H2O + ATP. We can investigate aerobic respiration in organisms by measuring the amount of oxygen they take in from the air and calculating the change in volume. Since carbon dioxide increases the gas volume, we should remove them first before doing measurements. 

Word equation for aerobic respiration, IGCSE & GCSE Chemistry revision notes

The word ‘anaerobic’, is the opposite of the word ‘aerobic’. The word ‘anaerobic’ means the absence of oxygen. In contrast to aerobic respiration, anaerobic respiration is the respiration that does not require any oxygen. Using oxygens for respiration is the most efficient way. However, some organisms, such as bacterias and many other microorganisms, have evolved over time to be able to perform respirations without any oxygens. Instead of oxygen, anaerobic cells use substances such as Sulfate, Nitrate, Sulfur, etc to make their cellular respiration work. Glucose is broken down without using any oxygen and the chemical reaction transfers those glucose energy to the cell.

 Anaerobic Respiration | Science - Quizizz

There are two kinds of chemical formula for anaerobic respiration. One is for animals and the other one is for plants. The chemical formula for animals is C6H12O6 →  2C3H6O3 (Glucose → Lactic acid). The respiration process usually takes place in muscle cells and lactic acid that’s produced instead of oxygen is the reason why we get terrible muscle cramps after we finish exercises that require anaerobic respiration. Lactic acids build up our muscle cells and lowers the Ph of the cells. Then, cells excrete lactic acids to the blood and send them to the liver. When acids are oxidised in the liver, only carbon dioxide and water become the left product. The reason why we continue to breathe heavily after the exercise is because our body goes through this whole process, which is known as ‘repaying the oxygen debt’, after we finish the exercise. 

For plants, the formula is known as C6H12O6 →  2C2H5OH+ 2CO2 (Glucose → Ethyl Alcohol + Carbon dioxide). The lactic acid that was changed from glucose needs to be oxidised later to carbon dioxide and water, to make this whole process work. However, the amount of ATP that’s produced after all this process is very small

There are a variety of similarities between aerobic and anaerobic respiration. Firstly, in the chemical formula for both of them, the end product is CO2 (carbon dioxide) and energy (ATP). Secondly, both aerobic and anaerobic respiration are the methods of generating energy, ATP, after the glucose is broken down, which also means that they both require glucose in order to work. Lastly, both of them are catabolic processes. The process could mainly be divided into two, anabolic and catabolic. Anabolic process where they take smaller units such as nutrients, cells, or amino acids and bond them together to create bigger structures. Opposingly to anabolic processes, catabolic process is when you take larger structures like protein, fats, or tissues and break them down into smaller units, such as cells or fatty acids. Since both aerobic and anaerobic respirations are the process of breaking down the glucose and making them into energy, they could be considered as catabolic processes.

 Difference Between Anabolism and Catabolism - An Overview

There are also some differences between aerobic and anaerobic respiration. The most basic factor that makes two respiration processes different is that aerobic respiration requires oxygen and anaerobic respiration does not. This fact makes the reactants in the chemical formula for both of them to be different. For aerobic respiration, the reactants are glucose and oxygens while it’s only glucose for anaerobic respiration. For aerobic respiration, products are water, ATP, and carbon dioxide (CO2). However, for anaerobic respiration, products could be ATP, ethyl alcohol, and carbon dioxide (CO2). Even though they both have ATP as the product, the amount of ATP they produce is very different. Aerobic produces a large amount of ATP (36 ATP) while anaerobic produces a very small amount (2 ATP). Also, aerobic respiration happens in cytoplasm and mitochondria when anaerobic respiration only occurs in cytoplasm of the cell. Lastly, higher organisms such as mammals use aerobic respiration while lower organisms such as bacterias and yeasts use anaerobic respiration.

Somin (Irene) Yoon

Member of Biology Society


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