Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:
b. Which steps involve decarboxylation (loss of CO₂)?

Verified step by step guidance

Step 1: Review the eight steps of the citric acid cycle (also known as the Krebs cycle or TCA cycle) to identify where decarboxylation occurs. Decarboxylation refers to the removal of a carbon atom from a molecule in the form of carbon dioxide (CO₂).

Step 2: Focus on the steps where a carbon atom is removed from the intermediate compounds of the cycle. This typically occurs when a six-carbon or five-carbon compound is converted into a smaller compound.

Step 3: Identify the enzymes involved in decarboxylation. In the citric acid cycle, decarboxylation is catalyzed by enzymes such as isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.

Step 4: Note the specific reactions: (1) The conversion of isocitrate to α-ketoglutarate involves the loss of one CO₂ molecule, and (2) the conversion of α-ketoglutarate to succinyl-CoA involves the loss of another CO₂ molecule.

Step 5: Summarize that decarboxylation occurs in two steps of the citric acid cycle: the isocitrate to α-ketoglutarate step and the α-ketoglutarate to succinyl-CoA step, both of which release CO₂ as a byproduct.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle, is a series of enzymatic reactions that occur in the mitochondria, playing a crucial role in cellular respiration. It processes acetyl-CoA to produce energy carriers like NADH and FADH₂, which are essential for ATP production. Understanding this cycle is vital for identifying specific reactions, such as decarboxylation, that contribute to the overall metabolic pathway.

Decarboxylation

Decarboxylation is a biochemical reaction that involves the removal of a carboxyl group (-COOH) from a molecule, releasing carbon dioxide (CO₂) as a byproduct. In the context of the citric acid cycle, certain steps involve decarboxylation, which is significant for the cycle's progression and energy yield. Recognizing these steps helps in understanding how carbon atoms are lost during metabolism.

Enzymatic Reactions

Enzymatic reactions are biochemical processes facilitated by enzymes, which are proteins that speed up chemical reactions without being consumed in the process. In the citric acid cycle, specific enzymes catalyze each step, including those that involve decarboxylation. Understanding the role of these enzymes is essential for grasping how the cycle operates and how energy is efficiently extracted from substrates.

Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:b. Which steps involve decarboxylation (loss of CO2)?