Biochemistry: Proteins, Enzymes, and Metabolism
Introduction
Biochemistry is the study of the chemical processes and substances occurring within living organisms. It focuses on the structure, function, and interactions of biological molecules such as proteins, enzymes, and metabolites. This article provides a detailed overview of these three constituents of biochemistry.
Proteins
Proteins are complex macromolecules that make up the building blocks of life. They consist of long chains of amino acids that are linked together by peptide bonds. Proteins have a diverse range of functions in the body, including:
- Structural support: collagen and keratin provide mechanical support to tissues such as skin and hair.
- Enzymatic catalysis: enzymes catalyze chemical reactions in the body, such as digesting food or breaking down toxins.
- Transport: hemoglobin transports oxygen in the blood.
- Hormonal regulation: insulin regulates glucose metabolism.
- Defense: antibodies defend the body against foreign substances.
Proteins are made up of 20 different amino acids, each with a unique side chain. The sequence of amino acids determines the structure and function of a protein. The primary structure is the linear sequence of amino acids, while the secondary structure involves the folding of the chain into alpha-helices, beta-sheets, or random coils. The tertiary structure is the overall 3D shape of the protein, while the quaternary structure results from the association of multiple protein subunits.
Enzymes
Enzymes are specialized proteins that catalyze chemical reactions in the body. They are highly specific and typically only catalyze one type of reaction. Enzymes lower the activation energy required for a reaction to occur, making it easier for the substrates to react. They do not alter the equilibrium position of the reaction, only the rate at which it occurs.
Enzymes typically have a specific active site where the substrate(s) bind. Enzyme-substrate interactions can be described by the lock-and-key or induced fit models. The lock-and-key model suggests that the substrate fit perfectly into the active site like a key in a lock. The induced fit model suggests that the active site is flexible and changes shape slightly when the substrate binds.
Metabolism
Metabolism is the set of chemical reactions that occur in living organisms to sustain life. It involves the synthesis and breakdown of complex molecules such as carbohydrates, fats, and proteins. Metabolic pathways are highly regulated and involve multiple enzymes working together to convert substrates into products.
There are two types of metabolic pathways: catabolic and anabolic. Catabolic pathways break down complex molecules into simpler ones, releasing energy in the process. Anabolic pathways synthesize complex molecules from simpler ones, requiring an input of energy.
Examples of catabolic pathways include glycolysis, which breaks down glucose into pyruvate, and the citric acid cycle, which oxidizes acetyl-CoA to CO2. An example of an anabolic pathway is protein synthesis, which involves linking amino acids together to form a protein.
Conclusion
Biochemistry is the study of biological molecules and the chemical processes that occur within living organisms. Proteins, enzymes, and metabolism are three important components of biochemistry. Proteins are macromolecules that have diverse functions in the body, while enzymes are highly specific proteins that catalyze chemical reactions. Metabolism involves the synthesis and breakdown of complex molecules and can be divided into catabolic and anabolic pathways.
