Question

Why is the reaction catalyzed by citrate synthase considered a condensation reaction?

Short answer

The citrate synthase reaction is a condensation reaction because it combines acetyl-CoA and oxaloacetate to form citrate with the release of water.

Step-by-step solution

Understand what a condensation reaction is

A condensation reaction occurs when two molecules combine to form a larger molecule, usually with the loss of a small molecule such as water. This type of reaction is common in biological systems for forming complex molecules.

Identify the reactants in the citrate synthase reaction

The reaction catalyzed by citrate synthase involves the combination of acetyl-CoA and oxaloacetate to form citrate. This is a key step in the citric acid cycle within cellular respiration.

Analyze the reaction mechanism

In the reaction, acetyl-CoA (a 2-carbon molecule) and oxaloacetate (a 4-carbon molecule) combine to form citrate (a 6-carbon molecule). During this process, the acetyl group from acetyl-CoA is transferred and combines with oxaloacetate, resulting in the formation of water as a by-product.

Link to the condensation reaction definition

Based on the definition from Step 1, the citrate synthase reaction is a condensation reaction because it combines two smaller molecules (acetyl-CoA and oxaloacetate) to form a larger molecule (citrate), while releasing a small molecule (water) as a by-product.

Key concepts

Condensation Reaction

A condensation reaction is a fundamental biochemical process. It occurs when two smaller molecules combine to form a larger molecule. Typically, this process releases a small molecule, often water. Such reactions are vital in creating complex biologically important molecules.

In the context of biochemical pathways, condensation reactions help in building up larger structures essential for cellular functions. For example, in protein synthesis, amino acids join through condensation reactions to form peptides and proteins.

Citrate Synthase

Citrate synthase is an enzyme crucial for the citric acid cycle. This enzyme catalyzes the initial step of the cycle, known as the citrate synthesis reaction. It combines acetyl-CoA and oxaloacetate to form citrate.

Enzymes like citrate synthase accelerate biochemical reactions. They bind to the reactants (or substrates) and convert them to products without being consumed in the process. For citrate synthase, efficiency and specificity in combining acetyl-CoA with oxaloacetate are essential for cellular respiration.

Citric Acid Cycle

The citric acid cycle, also called the Krebs cycle, is integral to cellular respiration. It occurs in the mitochondria of eukaryotic cells. Through a series of reactions, it generates energy by oxidizing acetyl-CoA.

The cycle produces ATP, NADH, and FADH2, which are energy carriers. These molecules are then used in the electron transport chain to produce more ATP. The citric acid cycle is crucial because it provides multiple points of entry for metabolites and integrates various metabolic pathways.

Acetyl-CoA

Acetyl-CoA stands for acetyl coenzyme A. It is a key intermediate in metabolic pathways like glycolysis and the citric acid cycle. This molecule is formed during the breakdown of carbohydrates, fats, and proteins. It carries an acetyl group (2 carbons) to the citric acid cycle.

Acetyl-CoA is significant because it links glycolysis and the citric acid cycle. Its acetyl group can enter the cycle and contribute to ATP production, an essential energy source for cells.

Oxaloacetate

Oxaloacetate is a four-carbon molecule that plays a central role in metabolism. In the citric acid cycle, it combines with acetyl-CoA to form citrate. Oxaloacetate is also involved in gluconeogenesis, the process of making glucose from non-carbohydrate sources.

The availability of oxaloacetate can regulate the pace of the citric acid cycle. Insufficient amounts can slow down energy production. Thus, maintaining levels of oxaloacetate is crucial for efficient metabolic functions in the cell.