Respiration

Respiration Definition

Respiration is a metabolic process where living cells obtain energy (ATP) by using oxygen and releasing carbon dioxide from the oxidation of complex organic substances.

What is Respiration?

Respiration is a metabolic process present in all organisms, where cells break down glucose to produce energy (ATP-Adenosine triphosphate). This biochemical process takes place within the cells and is crucial for various cellular functions.

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Types of Respiration

Respiration

Aerobic Respiration

When cells carry out oxidation of food materials, utilising molecular oxygen; the process is called aerobic respiration.  It is completed in three steps:

  1.  Pyruvic Acid Oxidation – occurs in the cytoplasm of cell.
  2. Krebs Cycle Reactions – takes place in the matrix of mitochondria.
  3. Electron Transport Chain – occur in the cristae membrane of mitochondria.

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Overall reaction of aerobic respiration is: 

C6H1206 + 602 → 6CO2 + 6H2O + 38ATP

Anaerobic Respiration

When cells carry out break down of nutrients without utilising molecular oxygen; the process is called anaerobic respiration. A number of micro-organisms including yeast derive energy through anaerobic respiration.

Phases of Respiration in Organisms

In prokaryotic cells, respiration happens in the cytosol and around the plasma membrane, while in eukaryotic cells, it occurs in the mitochondria, known as the powerhouse of the cell.

This process is akin to the internal combustion of a car engine, where organic compounds and oxygen are taken in, and water and carbon dioxide are released. The energy released powers the cell (or automotive).

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The three phases of respiration are:

Glycolysis

Glucose molecules undergo conversion to pyruvic acid, which then oxidizes into carbon dioxide and water, yielding acetyl-CoA. Glycolysis produces two ATP and NADH molecules. Pyruvate enters the mitochondria's inner matrix, where it undergoes oxidation in the Kreb's cycle.

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Oxidative Phosphorylation

Glucose molecules undergo conversion to pyruvic acid, which then oxidizes into carbon dioxide and water, yielding acetyl-CoA. Glycolysis produces two ATP and NADH molecules. Pyruvate enters the mitochondria's inner matrix, where it undergoes oxidation in the Kreb's cycle.

Citric Acid Cycle

This metabolic pathway is also referred to as the tricarboxylic acid cycle or Kreb’s cycle. In each phase of the citric acid cycle, two ATP molecules are generated. This cycle occurs within the mitochondrial matrix of a cell, where the electrons produced move across the mitochondrial matrix.

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Frequently Asked Questions on Respiration

Ans. The process through which organisms interact with the environment to exchange gases, particularly oxygen and carbon dioxide.

Ans. The respiratory system, including the lungs, facilitates breathing by bringing oxygen into our bodies (inspiration or inhalation) and expelling carbon dioxide (expiration or exhalation). This process is known as respiration.

Ans. Antoine Lavoisier

Ans. Biology textbooks commonly mention that cellular respiration can produce up to 38 ATP molecules from one oxidized glucose molecule (2 from glycolysis, 2 from the Krebs cycle, and approximately 34 from the electron transport system).

Ans. ATP serves as the primary source of energy for cellular use and storage.

Ans. Karl Lohmann and Jendrassik