Any work is propelled by a form of energy. Food is the source of energy for all cellular activities. Cellular respiration is the process through which cells generate energy in the form of adenosine triphosphate (ATP). Cellular respiration may be classified into two categories based on the oxygen demand: aerobic and anaerobic. The breakdown of glucose molecules releases energy during cellular respiration. Aerobic and anaerobic respiration are the two types of respiration that may be classified depending on how much oxygen is used.
The term "aerobic" implies "with air." As a result, aerobic respiration is the process of cellular respiration in which oxygen is used to create energy from food. Most plants and animals, including humans, birds, and other mammals, use this form of respiration. Aerobic respiration is the process through which glucose is burned or oxidised in the presence of oxygen to produce energy (ATP).
When we breathe, we intake oxygen-rich air and exhale carbon dioxide-rich air. When we breathe in, oxygen-rich air is delivered to all regions of our bodies and, eventually, to each cell. With the aid of oxygen, the meal, which contains glucose, is broken down inside the cell into carbon dioxide and water. The act of breaking down food particles generates energy, which our bodies subsequently use. The energy generated by aerobic respiration aids in the growth of plants and animals, including humans.
The following equation may be used to concisely describe the process:
Glucose + Oxygen → Carbon dioxide + Water + Energy
Aerobic respiration is split into three stages: glycolysis, the Krebs cycle, and the electron transport system. The cytoplasm and mitochondria are the sites of respiration.
1. Glycolysis: The lysis or breaking of carbohydrates is referred to as glycolysis. One molecule of the 6-carbon atom glucose is broken down into two molecules of 3-carbon pyruvic acid during glycolysis. This happens in the cytoplasm in the presence or absence of oxygen. So, finally, we have two pyruvic acid molecules, two ATP molecules, and two NADH electron transporting molecules.
2. The Krebs cycle: The citric acid cycle and the tricarboxylic acid cycle are two more names for the Kreb cycle. The generated pyruvic acid is transported to the mitochondrial matrix and transformed into acetyl CoA. Thus, two molecules of ATP are generated after several steps. In addition, two chemicals are produced: nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH2). They aid in the transport of electrons to the following stage.
3. Oxidative Phosphorylation and the Electron Transport System: ETS is entirely dependent on oxygen. High-energy electrons are transferred through a chain of electron carriers, including NADH, resulting in the formation of an electron gradient. ATPase eventually converts ADP to ATP via oxidative phosphorylation.
Finally, in eukaryotes, the total number of ATP molecules collected in a single respiration is 36, but in prokaryotes, it is 38.
Anaerobic respiration is a kind of cellular respiration that happens when oxygen is not available. Fermentation is another name for this process. They will not participate in the TCA cycle or the ETS. Pyruvic acid is produced as a result of incomplete glycolysis in this case. Pyruvic acid is further reduced, yielding carbon dioxide and ethanol in addition to ATP. This is referred to as alcoholic fermentation. The term "anaerobic" implies "without air." As a result, this kind of cellular respiration does not generate energy through the consumption of oxygen. When there is insufficient oxygen for some creatures to respire, they still require energy to survive.
Anaerobic respiration is also employed by multicellular organisms such as ourselves as a transient reaction to oxygen-depleted circumstances. For example, our bodies require a lot of energy when we do hard or intense activities like jogging, sprinting, cycling, or weight lifting. Because oxygen supply is restricted, our body's muscle cells turn to anaerobic respiration to meet the energy needs.
Glucose → Alcohol + Carbon dioxide + Energy
Fermentation occurs inside animal muscle cells under anaerobic circumstances, producing lactic acid and ATP. This is an illustration of lactic acid fermentation. When compared to aerobic respiration, the overall number of ATP molecules generated during fermentation is relatively little.
The use of oxygen in the process of cellular respiration is the primary distinction between anaerobic and aerobic respiration. As the name implies, aerobic respiration is the mechanism by which cells generate the energy they require by utilising oxygen. This process generates carbon dioxide as a byproduct and ATP, the cell's energy currency. As a result, lactic acid and ATP are produced as byproducts of this process.