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Cellular respiration


Respiration is an important biochemical process for us to maintain our daily life. It canproduce energy that is necessary for the function of the body. It provides oxygen to the cellsand to get rid of the waste gas, carbon dioxide. If without respiration, that organism woulddie, so this article is aimed to talk about how cell respiration is important and how it works.


What is cellular respiration and ATP

Cellular respiration is a series of metabolicprocesses that take place within a cell in which thebiochemical energy is harvested from an organicsubstance (e.g. glucose) and then stored in anenergy-carrying biomolecule (e.g. ATP) for use inenergy-requiring activities of the cell. This processgenerates usable ATP energy to support many otherreactions in the body. Adenosine triphosphate (ATP)is an organic compound that can be considered as auniversal energy carrier, transferring chemicalenergy within the cell for use in metabolic processessuch as biosynthesis, cell division and so on.


Two types of cellular respiration

(1)Anaerobic respiration

It is the process that without oxygen, releases less energy but more quickly than aerobicrespiration.

When it happens in yeast and plants, it is called alcoholic fermentation which means theglucose is broken down to produce ethanol and carbon dioxide, and also a very lessamount of energy (ATP). This process can be used commercially to produce bread, yoghurtand also alcoholic beverages.

When anaerobic respiration happens in muscle cells, it will give a totally different output.After we finish a vigorous exercise, we always feel soreness in our muscles, whether arm orleg, which is the effect of anaerobic breathing. It’s called lactic acid fermentation, whichmeans glucose is not completely broken down, so the amount of energy released is less.There is a build up of lactic acid in the muscle so that’s why we feel soreness after exercise.

(2)Aerobic respiration

This is a process by organisms that use oxygento produce large amounts of energy to drive thebulk production of ATP. This process is muchmore efficient and produces ATP more quicklythan anaerobic respiration. The reason why isbecause oxygen is an excellent electronacceptor for the chemical reactions involved ingenerating ATP.


The processes of respiration


It is a metabolic pathway that is taken part in cytosol, it can be literally translated as “sugarsplitting”, and it occurs with or without oxygen which means it also happens in anaerobicrespiration. This process converts 1 molecule of glucose into 2 molecules of pyruvate. It canproduce 2 molecules of pyruvate, ATP, NADH and water. This metabolic pathway was firstdiscovered in the early 19th century by three German biochemists: Gustav Embden, OttoNeMeyerhof and Jakub Karol Parnas, and it is known as the EMP(Embden-Meyerhof-Parnas) pathway. Link reaction

This process takes place in the mitochondrial matrix and converts pyruvate into an acetylcoenzyme A (acetyl CoA). This can produce reduced NAD and acetyl CoA but not produceenergy. Reduced NAD will be used in oxidative phosphorylation while the acetyl CoA will beused in the Krebs cycle.

Krebs cycle

Krebs cycle occurs within the mitochondrial matrix, aderivative of pyruvate decomposed to CO2. Itgenerates reduced NAD and a similar moleculecalled reduced FAD which are needed for oxidativephosphorylation. The acetyl group passes into acyclic reaction and combines with a 4-carbonmolecule to form a 6-carbon molecule. The CoA isreleased for reuse. The steps in the cycle removecarbon as CO2.

Oxidative Phosphorylation

Oxidative phosphorylation occurs withinmitochondrial cristae, it is the last stage of aerobicrespiration and also the part where most of the ATPis made. It uses the electrons that are being carriedby reduced NAD and reduced FAD that have beengenerated in the first three stages. During thisprocess, electrons derived from NADH and FADH2combine with O2, the energy released from thisredox reaction is used to drive the synthesis of ATPfrom ADP.


In summary, respiration is one of the mostimportant processes for our organisms tomaintain our life, cellular respiration is alsovery important, but who would have thought that the process of cellular respirationwould be so complex? Hope this article can help you have a deeper understandingof how the cells in our body work everyday!!

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