Match each stage of cellular respiration listed on the left with its precise subcellular l… — JAMB UTME

Match each stage of cellular respiration listed on the left with its precise subcellular location and characteristic biochemical process on the right.

GlycolysisCytosol; breaks down glucose into two molecules of pyruvate, generating net $2\text{ ATP}$ and $2\text{ NADH}$
Link Reaction (Pyruvate Oxidation)Mitochondrial matrix; decarboxylates pyruvate to form Acetyl-CoA, releasing $\text{CO}_2$ and producing $\text{NADH}$
Krebs CycleMitochondrial matrix; oxidizes acetyl groups to produce $\text{CO}_2$ , $\text{ATP}$ , $\text{NADH}$ , and $\text{FADH}_2$
Electron Transport Chain and ChemiosmosisInner mitochondrial membrane (cristae); uses electron movement to establish a proton gradient that drives ATP synthesis

Answer

Glycolysis corresponds to the cytosolic pathway yielding pyruvate, net

2\text{ ATP}

, and

2\text{ NADH}

. The Link Reaction corresponds to matrix oxidative decarboxylation forming Acetyl-CoA and

\text{CO}_2

. The Krebs Cycle corresponds to matrix oxidation of acetyl groups generating

\text{CO}_2

\text{NADH}

\text{FADH}_2

, and

\text{ATP}

. Electron Transport and Chemiosmosis correspond to cristae-bound electron transfer coupled to proton-gradient driven ATP synthesis.

Each stage of respiration occurs at a distinct cellular location optimized for its pathway: Glycolysis in the cytosol, the Link Reaction and Krebs Cycle within the mitochondrial matrix, and the Electron Transport Chain across the inner mitochondrial membrane (cristae).

Step-by-Step Solution

Identify the site and products of Glycolysis

Glycolysis is an anaerobic process taking place in the cytoplasm/cytosol, converting glucose to pyruvate with a net generation of

2\text{ ATP}

and

2\text{ NADH}

Enzymes for glycolysis are soluble in the cytosol, not membrane-bound in mitochondria.

Identify the site and products of the Link Reaction

Pyruvate enters the mitochondrial matrix where it undergoes oxidative decarboxylation to produce Acetyl-CoA,

\text{CO}_2

, and

\text{NADH}

This bridges cytosolic glycolysis to the matrix-localized Krebs cycle.

Identify the site and products of the Krebs Cycle

The cyclic breakdown of acetyl groups occurs in the mitochondrial matrix, producing

\text{CO}_2

, reduced coenzymes (

\text{NADH}

\text{FADH}_2

), and

\text{ATP}

Enzymes of the citric acid cycle are dissolved in the fluid matrix of the mitochondrion.

Identify the site and mechanisms of Electron Transport and Chemiosmosis

Electron carriers and ATP synthase complexes are located on the inner mitochondrial membrane (cristae), generating the vast majority of ATP via oxidative phosphorylation.

The folded cristae maximize surface area for respiratory electron carrier complexes.

Key Concept

Subcellular Localization and Pathways of Cellular Respiration

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