What is the difference between aerobic respiration and cellular respiration

Both begin with glycolysis - the splitting of glucose. Glycolysis see "Glycolysis" concept is an anaerobic process - it does not need oxygen to proceed. This process produces a minimal amount of ATP. The Krebs cycle and electron transport do need oxygen to proceed, and in the presence of oxygen, these process produce much more ATP than glycolysis alone.

Scientists think that glycolysis evolved before the other stages of cellular respiration. Cellular respiration that proceeds without oxygen is called anaerobic respiration. Then, about 2 or 3 billion years ago, oxygen was gradually added to the atmosphere by early photosynthetic bacteria cyanobacteria. After that, living things could use oxygen to break down glucose and make ATP.

Today, most organisms make ATP with oxygen. They follow glycolysis with the Krebs cycle and electron transport to make more ATP than by glycolysis alone. What is Cellular Respiration 4. Similarities Between Respiration and Cellular Respiration 5. In physiology, respiration is described as the movement of oxygen molecules from outside environment to the inner cells and the movement of carbon dioxide from inner cells to the outside environment in the opposite direction.

It is also known as breathing. The movement of oxygen into the cells is defined as inhalation. And the movement of carbon dioxide to the outside environment is defined as exhalation. Inhalation is an active process. The diaphragm is contracted, and internal height of the thoracic cavity is increased. The internal pressure decreases and atmospheric oxygen moves inside the respiratory tract. The exhalation is a passive process.

During the exhalation, the diaphragm relaxes and decreases the volume of the thoracic cavity. Then the internal pressure increases. Hence, carbon dioxide moves out of the respiratory tract to the outside environment.

Inhalation brings oxygen to the lungs, and the gas exchange takes place between air in the alveoli and blood in the pulmonary capillaries. The carbon dioxide in return moves from blood to alveoli air and out of the respiratory tract.

In biochemical means, the respiration is defined as cellular respiration. In the cellular respiration, the glucose is broken down into carbon dioxide and water in the presence of oxygen.

The resulted energy is stored in ATP where it is used in metabolism. Energy is needed to keep the life processes constantly. It is extremely important in life processes such as growth and development, movement, repair and the control of body temperature in mammals etc.

The cellular respiration is an energy generating biochemical reaction which takes place in all living cells including plant and animal cells. The energy that is released from glucose can be used in other living cells for biochemical reactions like catabolic and anabolic pathways. The cellular respiration is divided into two different pathways based on presence and absence of oxygen. If cellular respiration occurs in the presence of oxygen, it is called as aerobic respiration. It can occur in animal cells such as muscle cells as well as some prokaryotes.

In humans, the lactic acid build-up in muscles can occur during vigorous exercise when oxygen is not available. The aerobic respiration pathway is switched to the lactic acid fermentation pathway in the mitochondria which although produces ATP; it is not as efficient as aerobic respiration. The lactic acid build-up in muscles can also be painful. Alcoholic fermentation also known as ethanol fermentation is a process that converts sugars into ethyl alcohol and carbon dioxide.

It is carried out by yeast and some bacteria. Alcoholic fermentation is used by humans in the process of making alcoholic drinks such as wine and beer. During alcoholic fermentation, sugars are broken down to form pyruvate molecules in a process known as glycolysis.

Two molecules of pyruvic acid are generated during the glycolysis of a single glucose molecule. These pyruvic acid molecules are then reduced to two molecules of ethanol and two molecules of carbon dioxide. The pyruvate can be transformed into ethanol under anaerobic conditions where it begins by converting into acetaldehyde, which releases carbon dioxide and acetaldehyde is converted into ethanol.

Figure 5 shows an alcoholic fermentation equation. Methanogenesis is a process only carried out by anaerobic bacteria. These bacteria belong to the phylum Euryarchaeota and they include Methanobacteriales, Methanococcales, Methanomicrobiales, Methanopyrales, and Methanosarcinales.

Methanogens only occur in oxygen-depleted environments, such as sediments, aquatic environments, and in the intestinal tracts of mammals. There are 3 pathways for methanogenesis:.

This process involves activating acetate into acetyl-coenzyme A acetyl-CoA , from which a methyl group is then transferred into the central methanogenic pathway.

Acetoclastic methanogens split acetate in the following way:. Acetoclastic methanogenesis is performed by Methanosarcina and Methanosarcinales and is most often found in freshwater sediments. Here, it is thought that acetate contributes to around two-thirds of the total methane formation on earth on an annual basis. In methylotrophic methanogenesis, methanol or methylamines serve as the substrate instead of acetate. This process can be observed in marine sediments where methylated substrates can be found.

Some acetoclastic methanosarcinales and at least one member of the Methanomicrobiales can also use this second pathway. Finally, hydrogenotrophic methanogenesis is a process that is used by Methanobacteriales, Methanococcales, Methanomicrobiales, Methanopyrales, and Methanosarcinales i.

In this reaction, hydrogenotrophic methanogens use hydrogen for the reduction of carbon dioxide, carbon monoxide, or formate according to the following:. Although methanogenesis is a type of respiration, an ordinary electron transport chain is not used. Methanogens instead rely on several coenzymes, including coenzyme F, which is involved in the activation of hydrogen, and coenzyme M, which is involved in the terminal reduction of CH3 groups to methane Figure 6.

What are the 4 stages of cellular respiration? There are 4 stages of the cellular respiration process. These are Glycolysis, the transition reaction, the Krebs cycle also known as the citric acid cycle , and the electron transport chain with chemiosmosis. Glycolysis is a series of reactions that extract energy from glucose by splitting it into 2 molecules of pyruvate.

Glycolysis is a biochemical pathway that evolved long ago and is found in the majority of organisms. In organisms that perform cellular respiration, glycolysis is the first stage of the process. Before glycolysis begins, glucose must be transported into the cell and phosphorylated. In most organisms, this occurs in the cytosol. Glycolysis does refer to other pathways, one such pathway described is the Entner—Doudoroff pathway. This article concentrates on the EMP pathway.

Glycolysis takes place in 10 steps. See figure 7. The enzyme hexokinase phosphorylates glucose using ATP to transfer a phosphate to the glucose molecule to form glucosephosphate. This reaction traps the glucose within the cell. Glucosephosphate is isomerized into fructosephosphate. This involves the change of an aldose into a ketose. The enzyme phosphoglucose isomerase catalyzes this reaction.

A molecule of ATP provides the phosphate group. Phosphofructokinase PFK with magnesium as a cofactor phosphorylates glucosekinase to fructose 1,6-bisphosphate.

This enzyme catalyzes the transfer of a phosphoryl group from ATP to fructosephosphate. This reaction yields ADP and fructose 1, 6-bisphosphate. PFK is a significant enzyme in the regulation of glycolysis.

Citric acid is also known to inhibit the action of PFK. These first 3 stages of glycolysis have used up a total of 2 ATP molecules; hence it is known as the investment phase. The enzyme aldolase is utilized to split fructose 1, 6-bisphosphate into glyceraldehydephosphate GAP and dihydroxyacetone phosphate DHAP.

GAP is the only molecule that continues in the glycolytic pathway. At this point there are two molecules of GAP, the next steps are to fully convert to pyruvate. The phosphate group then attacks the GAP molecule and releases it from the enzyme to yield 1,3 bisphosphoglycerate, NADH, and a hydrogen atom. Phosphoglycerate kinase PGK with the help of magnesium converts 1,3 bisphosphoglycerate to 3-phosphoglycerate by removing a phosphate group.

Phosphoglycerate mutase rearranges the position of the phosphate group on 3-phosphoglycerate allowing it to become 2-phosphoglycerate. Enolase dehydrates 2 phosphoglycerate molecules by removing water. In aerobic respiration, the transition reaction occurs in the mitochondria. Pyruvate moves out of the cytoplasm and into the mitochondrial matrix. In anaerobic conditions, pyruvate will stay in the cytoplasm and be used in lactic acid fermentation instead.

The Krebs cycle, or also known as the citric acid cycle was discovered by Hans Adolf Krebs in It can be described as a metabolic pathway that generates energy.

This process happens in the mitochondrial matrix, where pyruvate has been imported following glycolysis. These products are generated per single molecule of pyruvate.

The products of the Krebs cycle power the electron transport chain and oxidative phosphorylation. Acetyl CoA enters the Krebs cycle after the transition reaction has taken place conversion of pyruvate to acetyl CoA. See figure 9. There are 8 steps in the Krebs cycle. Below reviews some of the principal parts of these steps and the products of Krebs cycle:. Acetyl CoA joins with oxaloacetate releasing the CoA group and producing citrate, a six-carbon molecule.

The enzyme involved in this process is citrate synthase. Citrate is converted to isocitrate by the enzyme aconitase. This involves the removal then the addition of water.

The ketone is then decarboxylated i. CO 2 removed by isocitrate dehydrogenase leaving behind alpha-ketoglutarate which is a 5-carbon molecule. Isocitrate dehydrogenase, is central in regulating the speed of the Krebs cycle citric acid cycle.

Oxidative decarboxylation takes place by alpha-ketoglutarate dehydrogenase. Succinyl-CoA is converted to succinyl phosphate, and then succinate. Succinate thiokinase other names include succinate synthase and Succinyl coenzyme A synthetase , converts succinyl-CoA to succinate, and free coenzyme A. Firstly, the coenzyme A at the succinyl group is substituted by a hydrogen phosphate ion.

Succinyl phosphate then transfers its phosphoric acid residue to guanosine diphosphate GDP so that GTP and succinate are produced. Succinate is oxidized to fumarate by succinate dehydrogenase.