Aerobic and Anaerobic Respiration - Differences & Overview

Aerobic and Anaerobic Respiration - Differences & Overview

Edited By Irshad Anwar | Updated on Oct 10, 2024 02:09 PM IST

Aerobic and anaerobic reactions are the most basic biochemical processes in the cellular respiration chain from where cells derive energy. This is one of the most important topics of Biology and it is included in the Class 11 Biology chapter, Respiration in Plants. This topic is important for the students preparing for exams like NEET, AIIMS and other paramedical courses. This article will compare and compare aerobic and anaerobic respiration, how they are defined, their structures, and physiological roles. There are also diagrams and some key exam preparation tips on how these reactions affect cellular function.

What is Respiration?

Respiration is one of the metabolic processes by which organisms synthesize energy, carbon dioxide and water out of oxygen and glucose. This process is crucial for the existence of all aerobic organisms because it is the only place where energy is produced that is paramount for cellular activities and physiological processes. In living organisms, respiration is not only identified to provide energy for metabolic functions but also has a significant role in regulating the body’s internal environment and supporting growth and development besides repair functions. Knowing or appreciating the respiratory process is significant to grasping the hardworking process of energy generation and usage in biological processes.

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Comparison between Aerobic and Anaerobic Respiration

Key Differences

Aerobic Respiration

Anaerobic Respiration

Oxygen Requirement

Requires oxygen

Does not require oxygen

ATP Yield

High (approximately 36-38 ATP per glucose)

Low (2 ATP per glucose)

By-products

Carbon dioxide and water

Lactic acid or ethanol and carbon dioxide

Efficiency

High efficiency

Low efficiency

What is Aerobic Respiration?

Aerobic respiration is a catabolic process in which all the cells in the body use glucose and oxygen to produce carbon dioxide, water and energy. It occurs in the presence of oxygen and it is the main means through which aerobic organisms generate ATP, or Adenosine triphosphate, the energy currency of cells.

Process of Aerobic Respiration

The process of aerobic respiration is given below-

Glycolysis

Glycolysis takes place in the cytoplasm of the cell and not in any of the cell organelles including the mitochondria.

Steps Involved

  • Glucose combines with a phosphate group to release vitamins and forms glucose-6-phosphate.

  • Glucose-6-phosphate is oxidatively decarboxylated to give fructose-6-phosphate.

  • The next step involves the phosphorylation of fructose-6-phosphate to undergo fructose-1,6-bisphosphate.

  • Fructose-1,6-bisphosphate is cleaved into 2 three-carbon molecules of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.

  • G3P is oxidised, and NAD+ is reduced to NADH In this process, there is the oxidation of G3P and NAD+ while NADH is reduced.

  • This is carried out through substrate-level phosphorylation.

  • Pyruvate accumulates as the terminal product of this process.

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Products Formed

Their products include 2 molecules of pyruvate.

  • 2 ATP (net gain)

  • 2 NADH

Krebs Cycle (Citric Acid Cycle)

The Krebs cycle occurs in the matrix part of the mitochondria.

Steps Involved

  • Citrate forms from acetyl-CoA by combining it with oxaloacetate.

  • Citrate is then oxidised to isocitrate.

  • Isocitrate is oxidised to alpha-ketoglutarate and simultaneously generates NADH.

  • AKG is converted to succinyl-CoA giving rise to NADH.

  • Succinyl-CoA is converted to succinate and in the process ATP (or GTP) is produced Many of the complexes are reviewed as follows;

  • Succinate is oxidised to fumarate yielding FADH2.

  • Fumarate is reduced to malate.

  • Malate is oxidised to oxaloacetate while generating NADH.

Products Formed

2 ATP (in each glucose molecule, these ATP’s are produced through the process of substrate-level phosphorylation).

  • 6 NADH

  • 2 FADH2

  • 4 CO2

Electron Transport Chain (ETC)

The electron transport chain is located within the inner layer of the mitochondria compartments known as the cristae membrane.

Steps Involved

  • NADH and FADH2 pass on their electrons to the electron transport chain.

  • Electrons are transferred through a sequence of protein structures.

  • The energy liberated from the electron is utilised in putting protons across the inner membrane with the creation of a proton gradient.

  • Protons move back through ATP synthase to synthesise ATP.

Role of Oxygen

Oxygen is the final receptor of electrons, with which it combines to form water through the addition of protons.

Products Formed

  • Approximately 34 ATP

  • Water (H2O)

What is Anaerobic Respiration?

Fermentation is a process of breaking down glucose in cells to release energy without using oxygen. This process, in contrast, is less efficient in creating ATP molecules than aerobic respiration, which creates fewer ATP molecules per glucose molecule and it is common in anaerobic conditions.

Types of Anaerobic Respiration

The different types of anaerobic respiration are:

Lactic Acid Fermentation

Lactic acid fermentation is experienced in some bacteria and animal cells particularly the muscle cells when oxygen is scarce. Here, pyruvate – a glycolysis end product – is converted by NAD+ into lactic acid, with NADH generated getting oxidised back to NAD+.

  • Skeletal muscle tissue cells during exercise & mainly during vigorous exercise.

  • Some of the bacteria include Lactobacillus species

Alcoholic Fermentation

Alcoholic fermentation takes place in yeast and some kinds of bacteria. In this process, pyruvate is again utilized, and it is transformed into ethanol and carbon dioxide. First, pyruvate is decarboxylated into acetaldehyde, and then it is reduced to ethanol with the help of NAD+; the NAD+ is returned to the cycle.

  • Yeast (Saccharomyces cerevisiae)

  • Some typical bacteria involve: Zymomonas mobilis

Tips, Tricks, and Strategies to Prepare for Aerobic Anaerobic Respiration

Given below are tips and tricks to prepare for aerobic anaerobic respiration:

  • Diagrams and Tables: Familiarize yourself with diagrams of aerobic and anaerobic pathways. Create a comparison table (like the one above) for quick revision.
  • Mnemonics: Use mnemonic devices to remember the steps of the Krebs cycle. For instance, “Citrate Is Krebs' Starting Substrate For Making Oxaloacetate” helps recall the order.
  • Flashcards: Prepare flashcards with key terms, such as “Glycolysis,” “Krebs Cycle,” and “Fermentation.”
  • Visualization Tools: Watch animations that illustrate the Krebs cycle, ETC.
  • Real-Life Applications: Relate concepts to daily activities, such as the burning sensation in muscles due to lactic acid accumulation.

Types of Questions and Weightage of Aerobic and Anaerobic Respiration in Various Competitive Exams

The table indicates the weightage and types of questions asked from aerobic anaerobic respiration in different exams:

Exam TypeTypes of QuestionsWeightage
CBSE Board Exams
Definitions, differences between aerobic and anaerobic reactions, diagram explanations3-4%
NEET
MCQs on steps of each process, ATP yield, and end products2-3%
AIIMSAssertion and reason questions related to aerobic and anaerobic processes2-3%
Nursing Entrance Exams
Scenario-based questions on muscle function during anaerobic respiration1-3%
Paramedical ExamsTrue/False questions on oxygen usage and anaerobic respiration products1-3%


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Frequently Asked Questions (FAQs)

1. What is the main difference between aerobic and anaerobic respiration?

The areas of divergence between aerobic and anaerobic respiration are in the need for oxygen. The former is aerobic respiration in which oxygen is used while the latter is anaerobic respiration in which oxygen is not used.

2. How much ATP is produced in aerobic respiration?

Aerobic respiration forms about 36-38 molecules of ATP food one glucose molecule.

3. What are the by-products of anaerobic respiration?

Anaerobic respiration has two by-products: lactic acid when the fermentation is lacto-acid type while ethanol and carbon dioxide are by-products when the process is alcoholic one.

4. Why is aerobic respiration considered more efficient than anaerobic respiration?

This is more efficient than anaerobic respiration mainly because aerobic respiration is capable of producing a much higher ATP per glucose molecule and helps in utilizing the energy stored in glucose to the optimum level.

5. In which part of the cell does the Krebs cycle occur?

Fermentation takes place in the mitochondrion of the cell and is known as the Krebs cycle.

6. What is aerobic and anaerobic with example?

Aerobic respiration is the production of energy that utilizes oxygen. For example, humans perform aerobic respiration during their daily routines.
Anaerobic respiration is the production of energy without the use of oxygen, typically when the environment has no oxygen. For example, yeast performs anaerobic respiration to create ethanol in brewing.

7. What are the 4 stages of aerobic respiration?

The four stages of aerobic respiration are:

  • Glycolysis: glucose breakdown
  • Link Reaction: connecting glycolysis to the Krebs cycle
  • Krebs Cycle: where energy carriers are produced
  • Electron Transport Chain: where most of the ATP is generated.
8. What is the concept of anaerobic respiration?

Anaerobic respiration is a process of generating energy without the help of oxygen; in this process, glucose is partially broken down, thereby producing less energy than in the case of aerobic respiration, and its byproducts may be lactic acid or ethanol.

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