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A topic from the subject of Biochemistry in Chemistry.

  • 10 months ago
  • 6 min read
Citric Acid Cycle
Introduction
The citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions that occur in the mitochondria of eukaryotic cells. It is a key part of cellular respiration, the process by which cells generate energy from glucose.
Basic Concepts
The citric acid cycle is a cyclic pathway, meaning that the products of one reaction are used as the substrates for the next. The cycle consists of eight steps, each of which is catalyzed by a specific enzyme.
The cycle is named after citric acid, which is one of the intermediate molecules in the pathway.Equipment and Techniques Spectrophotometer
Spectrophotometer cuvettes Pipettes
Centrifuge Homogenizer
Chemicals Citric acid
Oxaloacetate Acetyl-CoA
NAD+ FAD
Coenzyme ATypes of Experiments Measurement of enzyme activity: This experiment measures the rate of a specific enzyme-catalyzed reaction in the citric acid cycle.
Identification of intermediates:This experiment identifies the different intermediates in the citric acid cycle. Determination of the pathway of the citric acid cycle: This experiment determines the order of the reactions in the citric acid cycle.
Data Analysis
The data from the experiments are typically analyzed using statistical methods. The results of the experiments can be used to create a model of the citric acid cycle.
Applications
The citric acid cycle is a target for many drugs, including antibiotics and anticancer drugs. The citric acid cycle is also used in the production of biofuels.
Conclusion
The citric acid cycle is a key part of cellular respiration. It is a cyclic pathway that consists of eight steps. The cycle is responsible for the generation of energy from glucose. The citric acid cycle is also a target for many drugs and is used in the production of biofuels.

Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle or tricarboxylic acid (TCA) cycle, is a series of chemical reactions that occur in the mitochondria of eukaryotic cells. It is a key part of cellular respiration, the process by which cells generate energy in the form of ATP.
Key Points
The citric acid cycle is a cyclic pathway, meaning that it starts and ends with the same molecule (oxaloacetate). The cycle consists of eight steps, each of which is catalyzed by a specific enzyme.
The cycle uses acetyl-CoA as the starting substrate, and produces ATP, NADH, and FADH2 as energy carriers. The cycle is also a source of intermediates for other metabolic pathways, such as the synthesis of amino acids, nucleotides, and fatty acids.
Main Concepts
Acetyl-CoAis the primary substrate for the citric acid cycle. It is derived from the breakdown of glucose during glycolysis. Oxaloacetate is the starting and ending molecule of the cycle. It is regenerated at the end of the cycle to prepare for the next turn.
Citrateis the first intermediate formed in the cycle. It is formed by the condensation of acetyl-CoA and oxaloacetate. Isocitrate is the second intermediate in the cycle. It is formed by the isomerization of citrate.
α-Ketoglutarateis the third intermediate in the cycle. It is formed by the oxidative decarboxylation of isocitrate. Succinyl-CoA is the fourth intermediate in the cycle. It is formed by the oxidative decarboxylation of α-ketoglutarate.
Succinateis the fifth intermediate in the cycle. It is formed by the hydrolysis of succinyl-CoA. Fumarate is the sixth intermediate in the cycle. It is formed by the dehydration of succinate.
Malateis the seventh intermediate in the cycle. It is formed by the hydration of fumarate. Oxaloacetate is the eighth and final intermediate in the cycle. It is formed by the oxidation of malate.
The citric acid cycle is a complex and highly regulated process that is essential for cellular respiration. It provides the energy and intermediates necessary for the cell to function properly.

Experiment: Citric Acid Cycle

Objective:

To demonstrate the citric acid cycle, a series of chemical reactions that occur in the mitochondria of cells to produce energy.


Materials:

  • Citric acid
  • Isocitric acid
  • α-Ketoglutarate
  • Succinyl-CoA
  • Fumarate
  • Malate
  • Oxaloacetate
  • Enzyme mix (containing citrate synthase, aconitase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, succinyl-CoA synthetase, fumarase, malate dehydrogenase, and oxaloacetate dehydrogenase)
  • pH buffer
  • Spectrophotometer

Procedure:
1. Prepare the reaction mixture. Mix citric acid, enzyme mix, and pH buffer in a cuvette.
2. Start the reaction. Add isocitric acid to the cuvette and mix.
3. Monitor the reaction. Use the spectrophotometer to measure the absorbance of the reaction mixture at 340 nm.
4. Repeat steps 2-3. Add the remaining intermediates (α-ketoglutarate, succinyl-CoA, fumarate, malate, and oxaloacetate) to the cuvette, one at a time, and monitor the absorbance.
Key Procedures:

  • Controlling pH: The pH of the reaction mixture must be maintained at around 7.4 for the enzymes to function properly.
  • Using a spectrophotometer: The absorbance at 340 nm is used to measure the production of NADH, which is a product of the citric acid cycle.
  • Adding intermediates: Each intermediate is added to the reaction mixture in sequence to demonstrate the progression of the cycle.

Significance:
The citric acid cycle is a central metabolic pathway that provides energy to cells. By demonstrating the citric acid cycle in this experiment, students can visualize and understand this important process. The experiment can also be used to teach about enzyme function and the regulation of metabolic pathways.

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