Catabolic

Catabolic

The term "catabolic" refers to the metabolic pathways that break down molecules into smaller units and release energy. These pathways are crucial for maintaining the energy balance in living organisms and are a fundamental aspect of metabolism. Catabolic processes are essential for the degradation of complex molecules such as carbohydrates, fats, and proteins into simpler forms that can be utilized by the body.

Overview

Catabolism is one half of the metabolic process, the other being anabolism, which involves the building up of complex molecules from simpler ones. Together, these processes constitute the metabolic pathways that sustain life.

Catabolic reactions are typically exergonic, meaning they release energy. This energy is often captured in the form of adenosine triphosphate (ATP), which is then used to power various cellular activities.

Key Catabolic Pathways

Glycolysis

Glycolysis is the catabolic pathway that breaks down glucose into pyruvate, yielding ATP and NADH in the process. It is the first step in cellular respiration and occurs in the cytoplasm of cells.

Citric Acid Cycle

Also known as the Krebs cycle or TCA cycle, the citric acid cycle is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Beta-Oxidation

Beta-oxidation is the catabolic process by which fatty acid molecules are broken down in the mitochondria to generate acetyl-CoA, which enters the citric acid cycle, and NADH and FADH2, which are used in the electron transport chain.

Proteolysis

Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. This process is essential for the recycling of amino acids and the removal of damaged or misfolded proteins.

Regulation of Catabolic Pathways

Catabolic pathways are tightly regulated to ensure that energy production is matched to the energy needs of the cell. This regulation is achieved through various mechanisms, including allosteric regulation of enzymes, covalent modification of enzymes, and control of gene expression.

Clinical Relevance

Disorders of catabolism can lead to various metabolic diseases. For example, defects in the enzymes involved in the breakdown of fatty acids can lead to conditions such as medium-chain acyl-CoA dehydrogenase deficiency (MCADD).

Also see

• Anabolic
• Metabolism
• Cellular respiration
• ATP
• Enzyme