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Aerobic respiration is the process involved in the production of energy in presence of oxygen. Aerobic respiration is a biological process where green plants make their food by releasing energy which occurs in four different steps. Aerobic Respiration and anaerobic respiration are two types of cellular respirations that are important processes for plants and animals in order to survive. Cellular respiration is the process by which mitochondria is used to convert the energy in food to ATP. Unlike animals, plants do not have a special organ for the exchange of gases except lenticels and stomata.
Also Read: Aerobic and Anaerobic Respiration
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Key Terms: Aerobic respiration, ATP, plants, Cellular respiration, Photosynthesis, Anaerobic respiration, Biological process
What is Aerobic Respiration?
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Aerobic respiration is a process in which food glucose is completely oxidized into carbon dioxide and water with the release of energy, in the presence of atmospheric oxygen. Carbohydrates, Fats, and Proteins are consumed as reactants. However, aerobic respiration is the preferred method of pyruvate breakdown in glycolysis.
Aerobic Respiration
Aerobic respiration process requires pyruvate to the mitochondria to be fully oxidized by citric acid cycle. This process results in producing carbon dioxide and water, and the energy transferred is used to break bonds in ADP to add a third phosphate group to form ATP (adenosine triphosphate), by substrate-level phosphorylation, NADH and FADH2
Simplified reaction of Aerobic Respiration Process is:
C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) + heat
\(\Delta\)G = −2880 kJ per mol of C6H12O6
Please note: The negative ΔG indicates that the reaction can occur spontaneously.
The video below explains this:
Aerobic Respiration Detailed Video Explanation:
Chemical reaction of aerobic respiration is:
| Glucose (C6H12O6) + oxygen 6 (O2) carbon dioxide 6 (CO2) + water 6 (H2O) + energy (ATP) |
Aerobic Respiration: Frequently Asked Questions
Ques. Can aerobic respiration occur without oxygen?
Ans. Oxygen is the final electron acceptor at the end of the electron transport chain of aerobic respiration. In the absence of oxygen, only a few ATP are produced from glucose. In the presence of oxygen, many more ATP are made.
Ques. What are the end products of aerobic respiration?
Ans. End products of aerobic respiration are: respiratory substrate that is fully oxidised to produce carbon dioxide, water and energy in a series of enzymatic reactions.
Ques. Why does aerobic respiration transfer more energy?
Ans. Aerobic respiration produces more energy than anaerobic respiration because in aerobic respiration, there is a complete breakdown of glucose molecules into CO2 and H2O. This occurs along with 38 ATP. However, in anaerobic respiration, the glucose only undergoes glycolysis and then either ethanol is formed or lactic acid is formed along with 2 ATP.
Checkout Important Question on: Respiration
Steps of Aerobic Respiration
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Aerobic respiration is a process of four stages: glycolysis, link reaction, Krebs cycle and oxidative phosphorylation.
- Glycolysis
Glycolysis is the cytosol of the cell within which the primary step of aerobic respiration takes place. In this process, two ATP and two NADH molecules are formed from the glucose molecule which is later used in the process of aerobic respiration. Glycolysis is the process that involves the splitting of a glucose molecule into pyruvic acid.
Steps of Aerobic Respiration
- Link Reaction
The link reaction stage in cellular respiration “links” two other stages. Link reaction takes products of the first stage, glycolysis, and converts them into reactants that will enter Krebs cycle. Primary product of glycolysis is the 3-carbon compound pyruvate.
- Krebs Cycle
In the citric acid or the Krebs cycle, citric acid is produced when acetyl coenzyme is combined with oxaloacetate. The citric acid cycle produces 1 molecule of ATP and 2 molecules of carbon dioxide.
Tricarboxylic Acid Cycle
- Oxidative Phosphorylation
Oxidative phosphorylation is a process where energy is harnessed through a series of protein complexes embedded in the inner-membrane of mitochondria (called the electron transport chain and ATP synthase) to create ATP.
Steps of Aerobic Respiration: Frequently Asked Questions
Ques. Which step is not necessary in aerobic respiration?
Ans. Glycolysis, the first step in all types of cellular respiration is anaerobic and does not require oxygen. If oxygen is present, the cycle will continue on to the Krebs cycle and oxidative phosphorylation.
Ques. What are the main steps in aerobic respiration and where does it take place?
Ans.The main steps of aerobic respiration are Glycolysis- Cytoplasm; Krebs cycle- Matrix of mitochondria; Electron transport system- Inner mitochondrial membrane; and Oxidative phosphorylation- Oxysome in the inner mitochondrial membrane.
Ques. What is the significance of stepwise release of energy in aerobic respiration?
Ans. The respiratory substrates enter and withdraw from the cycle as required. ATP is used wherever required and enzymatic rates are generally controlled. This stepwise release of energy makes the system more efficient in obtaining and storing energy.
Respiratory Quotient
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The respiratory quotient is the ratio of carbon dioxide released and the oxygen consumed while food is being metabolized. The RQ of anaerobic respiration is infinite. The reason being, in anaerobic respiration, total volume of oxygen consumed is zero as this process occurs in the absence of oxygen and only carbon dioxide is produced.
Thus, RQ = CO2 / O2 = 2/0 = infinity
RQ = volume of carbon dioxide evolved volume of oxygen consumed
RQ reduces to 1 when carbohydrate is completely oxidized. RQ is less than 1 when respiration uses fat. RQ is 0.9 when protein is taken as the respiratory substrate.
Also Read: Photochemical Reactions
Things to Remember
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- The byproducts of the reaction are carbon dioxide, water, and energy
- All multicellular organisms which include plants, animals, and other living organisms experience aerobic respiration
- Aerobic respiration is the modification of photosynthetic machinery.
- The process of splitting cellulose releases 2900 KJ energy which produces ATP
- ATP molecules are also known as adenosine triphosphate molecules that have various usages when the cell needs energy. The energy which is obtained from the breakdown of food is stored in the body of the animals in the form of ATP.
- There are two types of respiration – aerobic and anaerobic respiration. The former takes place in the presence of oxygen whereas the latter takes place in the absence of oxygen.
- The process of fermentation in yeast is an example of anaerobic respiration which is defined as the breakdown of glucose in the absence of oxygen.
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Sample Questions
Ques. What are the various kinds of aerobes? (2 Marks)
Ans. The different categories of aerobes are:
- Facultative aerobes: grows with or without oxygen
- Obligate aerobes: mandatory oxygen needed to grow
- Microaerophiles: needs oxygen to grow but cannot survive in a surrounding of oxygen.
Ques. Why is aerobic respiration important? (2 Marks)
Ans. Aerobic respiration is the process in which energy is released by breaking down the food in the body. Carbon dioxide is one of the byproducts of the process which is used for photosynthesis and produces carbohydrate food. Plants absorb water through this process. Cell division in plants happens due to respiratory energy.
Ques. Where does aerobic and anaerobic respiration take place? (2 Marks)
Ans. Cellular respiration is of two kinds- aerobic (using oxygen) and anaerobic respiration (without oxygen). Aerobic respiration takes place in the cytoplasm (glycolysis) and mitochondrion whereas anaerobic respiration takes place only in the cytoplasm.
Ques. What is an electron transport system? (2 Marks)
Ans. Electron transport system is the metabolic path that transports electrons from one carrier to another. It is located in the inner membrane of the mitochondrion. During the citric acid cycle, electrons are produced from NADH in the mitochondrial matrix and are oxidized by a dehydrogenase. The electron transport system releases energy which is used to synthesize ATP.
Ques. Why is oxygen important in the process of aerobic respiration in the context of the electron transport system? (2 Marks)
Ans. The existence of oxygen is essential for complete aerobic respiration. It escalates the process by removing the hydrogen from the system. It plays the role of the last hydrogen receptor. In the stage of photophosphorylation, light energy is used for the production of proton gradient which is why it is known as oxidative photophosphorylation. ATP will not be produced if electrons cannot pass through the co-enzymes and there will be no proton pump which is impossible without oxygen.
Ques. Why is the respiratory pathway also known as the amphibolic pathway? (2 Marks)
Ans. In order to enter the respiratory pathway, fatty acids and proteins are reduced to acetyl CoA. During the synthesis of proteins and fats, substances are removed from the respiratory pathway and are used in anabolism. Anabolism is the formation of the substances and catabolism is the breakdown of the substances. The respiratory pathway is also known as the amphibolic pathway as both the processes of anabolism and catabolism take place there.
Ques. Why is aerobic respiration considered to be more efficient than anaerobic respiration? (2 Marks)
Ans. Aerobic and anaerobic have various characteristics. Aerobic respiration is more efficient than anaerobic respiration because a single molecule of glucose can produce 36 ATP molecules in aerobic respiration whereas, in anaerobic respiration, a single molecule of glucose can yield only 2 molecules of ATP.
Ques. Describe in detail the aerobic oxidation of pyruvic acid. (3 Marks)
Ans. Pyruvic acid generated in the crystal is transported to mitochondria, which initiates the second phase of respiration. Before pyruvic acid enters the Kreb’s cycle, one of its three carbon atoms gets oxidized to carbon dioxide in the reaction (oxidative decarboxylation).
At first, Pyruvate is decarboxylated and then oxidized by the enzyme pyruvate dehydrogenase. The combination of remaining two-carbon acetate unit is readily accepted by a sulfur-containing compound coenzyme A to form acetyl COA. During the process, NAD is reduced to NADH.
This process is shown as:
Aerobic Oxidation of Pyruvic Acid
During this process, two molecules of NADH are produced, and thus, it results in a net gain of 6ATP molecules.
(2 NADH + 3 = 6 ATP). 2 molecules of pyruvic acid produced during glycolysis.
Ques. Calculate the efficiency of respiration in the living system. (4 Marks)
Ans. During aerobic respiration, O2 is consumed and CO2 is released. The ratio of the volume of CO2 evolved to the volume of O2 consumed in respiration is called respiratory quotient (RQ) or respiratory ratio.
\(RQ = \frac{Volume of CO_2 evolved}{Volume of O_2 consumed}\)
The RQ (respiratory quotient) depends upon the respiratory substrate. When a carbohydrate is used as a substrate.
C6H12O6 - 2C2H5OH + 2CO + Energy (247 K.J)
Total energy yield from 38 ATP molecules comes to 1298 kJ. The energy released by one molecule of glucose on complete oxidation is 2870 kJ. Thus, the efficiency is 45%. Much of the energy generated during respiration is released in the form of heat.
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