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Respiration - Aerobic respiration

Grade 12IGCSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Aerobic respiration is the chemical process by which cells break down glucose (C6H12O6C_6H_{12}O_6) in the presence of oxygen (O2O_2) to release a high yield of energy in the form of ATPATP (Adenosine Triphosphate).

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The process occurs primarily within the mitochondria of eukaryotic cells, though the first stage (Glycolysis) occurs in the cytoplasm.

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The overall process involves four main stages: Glycolysis, the Link Reaction, the Krebs Cycle, and the Electron Transport Chain (Oxidative Phosphorylation).

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The balanced chemical equation for aerobic respiration is: C6H12O6+6O2→6CO2+6H2O+EnergyC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}.

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Carbon dioxide (CO2CO_2) and water (H2OH_2O) are the metabolic waste products that are excreted from the body via gas exchange and the renal system.

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The efficiency of aerobic respiration is significantly higher than anaerobic respiration, producing approximately 3636 to 3838 molecules of ATPATP per molecule of glucose, compared to only 22 ATPATP in anaerobic conditions.

📐Formulae

C6H12O6+6O2→6CO2+6H2O+Energy (ATP)C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (ATP)}

ADP+Pi+Energy→ATPADP + P_i + \text{Energy} \rightarrow ATP

Respiratory Quotient (RQ)=Volume of CO2 producedVolume of O2 consumed\text{Respiratory Quotient (RQ)} = \frac{\text{Volume of } CO_2 \text{ produced}}{\text{Volume of } O_2 \text{ consumed}}

💡Examples

Problem 1:

Calculate the number of molecules of O2O_2 required to fully oxidize 55 molecules of glucose (C6H12O6C_6H_{12}O_6) during aerobic respiration.

Solution:

3030 molecules of O2O_2

Explanation:

According to the balanced chemical equation C6H12O6+6O2→6CO2+6H2OC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O, the molar ratio of glucose to oxygen is 1:61:6. Therefore, for 55 molecules of glucose, the oxygen required is 5×6=305 \times 6 = 30 molecules of O2O_2.

Problem 2:

A respirometer measures that an organism consumes 120 cm3120 \text{ cm}^3 of O2O_2 and produces 120 cm3120 \text{ cm}^3 of CO2CO_2. Calculate the Respiratory Quotient (RQRQ) and identify the substrate being respired.

Solution:

RQ=1.0RQ = 1.0; Substrate is Carbohydrate (Glucose).

Explanation:

Using the formula RQ=CO2 producedO2 consumedRQ = \frac{CO_2 \text{ produced}}{O_2 \text{ consumed}}, we get RQ=120120=1.0RQ = \frac{120}{120} = 1.0. An RQRQ value of 1.01.0 typically indicates that the substrate being oxidized is a carbohydrate, such as glucose (C6H12O6C_6H_{12}O_6).

Aerobic respiration - Revision Notes & Key Diagrams | IGCSE Grade 12 Biology