Question

Match Column-I with Column-II and select the correct option from the codes given below. Column-I \(\quad\) Column-II A. Glycolysis (i) Inner mitochondrial membrane B. TCA cycle (ii) Mitochondrial matrix C. ETS (iii) Cytoplasm (a) \(\mathrm{A}\)-(iii), B-(i), C-(ii) (b) \(A-(i i i), B-(i i), C-(i)\) (c) \(\quad A-(i), B-(i i), C-(i i i)\) (d) \(A\)-(ii), B-(i), C-(iii)

Short answer

A-(iii), B-(ii), C-(i), which corresponds to option (b) A-(iii), B-(ii), C-(i).

Step-by-step solution

Match A: Glycolysis

Identify the location where glycolysis occurs in a cell. Glycolysis is a series of reactions that convert glucose into pyruvate and take place in the cytoplasm. Thus, A should be matched with (iii).

Match B: TCA cycle

Determine where the TCA (Tricarboxylic Acid) cycle, also known as the Citric Acid cycle or Krebs cycle, occurs. It takes place in the mitochondrial matrix. Therefore, B should be matched with (ii).

Match C: ETS

ETS stands for Electron Transport System. It is located in the inner mitochondrial membrane where it participates in oxidative phosphorylation. So, C should be matched with (i).

Choose the correct option

Based on the previous matches, the correct combination is A-(iii), B-(ii), C-(i). Look for this combination in the given options.

Key concepts

Glycolysis

Glycolysis is a fundamental energy-producing process that can be aptly described as the body's way of turning sugar into power without using oxygen. This happens in the cytoplasm of cells and serves as a universal energy extraction route. Think of it as the first step in the journey of glucose metabolism.

During this process, a single glucose molecule is painstakingly split into two molecules of pyruvate. This division isn't just a simple split; it involves a sequence of ten enzyme-driven reactions. These reactions can be grouped into two phases: the energy investment phase, where the cell uses ATP to get the process going, and the energy payoff phase, which yields a net gain of ATP and NADH for the cell.

As a source of quick and readily available energy, especially important when oxygen is scarce, glycolysis is a critical survival mechanism for cells. However, it serves not only to provide energy but also to generate building blocks for other essential cellular processes.

TCA cycle

Often hailed as the central hub of metabolic processes, the TCA cycle—which stands for Tricarboxylic Acid cycle, also widely known as the Citric Acid cycle or Krebs cycle—is where things get more oxygen-dependent and complex.

The stage for the TCA cycle is the mitochondrial matrix, a space within the organelle known as the powerhouse of the cell. Here, pyruvate, which was generated during glycolysis, undergoes conversion into acetyl-CoA. Acetyl-CoA then enters the cycle, where it's systematically dismantled to CO₂ in a cyclic series of oxidation reactions.

By tearing down acetyl-CoA, the cell captures high-energy electrons in the form of NADH and FADH₂. These molecules are like charged batteries, full of juice to later power another crucial process, the electron transport system (ETS). The cycle also replenishes intermediates for amino acid synthesis and other vital cellular operations, embodying the essence of cellular multitasking.

Electron Transport System (ETS)

The Electron Transport System (ETS), which is situated in the inner mitochondrial membrane, is the last leg in the marathon of cellular respiration. It's here that the cell finally cashes in on the high-energy electrons it has been saving up.

In the ETS, a series of proteins called electron carriers pass electrons from one to the other in a relay race. The energy released from these electron exchanges is used to pump protons across the mitochondrial membrane, creating a proton gradient. This gradient is akin to water stored high in a dam—it's potential energy, waiting to be unleashed.

This stored energy is tapped by the enzyme ATP synthase, which functions much like a turbine in a hydroelectric dam. As the protons flow back across the membrane through ATP synthase, their movement generates ATP, the primary currency of energy in the cell. It is this process of oxidative phosphorylation that is oxygen dependent and produces the bulk of ATP during respiration, illustrating why oxygen is so vital for life as we know it.