A common group transfer reaction in biological systems is one that is used to produce α-amino acids that can then be used for protein synthesis. The transfer of an amine functional group from one molecule to another is common example of this type of reaction and is shown in Figure 7.3 below.įigure 7.3 Transfer of an Amine Functional Group. In group transfer reactions, a functional group will be transferred from one molecule that serves as the donor molecule to another molecule that will be the acceptor molecule. Note that all of these reaction types require an enzyme catalyst (usually a specific protein) to speed up the rate of the reactions within biological systems. This section will give you a brief introduction to these six types of reactions and then the following section will focus more in-depth on oxidation-reductions and how they are critical for the formation of the major form of cellular energy, adenosine triphosphate (ATP). These include group transfer reactions, the formation/removal of carbon-carbon double bonds, isomerization reactions, ligation reactions, hydrolysis reactions, and oxidation-reduction reactions. Within biological systems there are six major classes of biochemical reactions that are mediated by enzymes. (B) In the Induced Fit Model, substrate interaction with the enzyme causes the shape of the enzyme to change to better fit the substrate and mediate the chemical reaction.įigure 7.2A was modified from Socratic and Figure 7.2B was modified from Concepts in Biology (A) In the Lock and Key Model, substrates fit into the active site of the enzyme with no further modifications to the enzyme shape required. This can occur by a lock and key model where the reactant is the exact shape of the enzyme binding site, or by an induced fit model, where the contact of the reactant with the protein causes the shape of the protein to change in order to bind to the reactant.įigure 7.2 Mechanisms of Enzyme-Substrate Binding. Enzyme shape is critical to the function of the enzyme as it determines the specific binding of a reactant. Enzymes can also allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. In addition, enzymes can provide a mechanism for cells to regulate the rate of a metabolic reaction in response to changes in the cell’s environment or to signals from other cells, through the activation or inhibition of the enzymes activity. Enzymes are crucial to metabolism because enzymes act as catalysts – they allow a reaction to proceed more rapidly.
#OXYGEN FORENSIC SUITE 7.4 FREE SERIES#
The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. Catabolic reactions usually release energy whereas anabolic processes usually require energy.įigure is modified from Metabolism Overview Catabolic reactions involve the breakdown of molecules into smaller components, whereas anabolic reactions build larger molecules from smaller molecules. Usually, catabolism releases energy, and anabolism consumes energy.įigure 7.1 Catabolic and Anabolic Reactions. Metabolic reactions may be categorized as catabolic– the breaking down of compounds (for example, the breaking down of proteins into amino acids during digestion) or anabolic – the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). (The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transport of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediate metabolism.) These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Overall, the three main purposes of metabolism are: (1) the conversion of food to energy to run cellular processes (2) the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and carbohydrates and (3) the elimination of waste products. We have seen examples of metabolic processes in the primary and secondary metabolites covered in Chapter 6. Metabolism is the set of life-sustaining chemical reactions in organisms. 7.1 What is Metabolism? 7.2 Common Types of Biological Reactions 7.3 Oxidation and Reduction Reactions and the Production of ATPħ.4 Reaction Spontaneity 7.5 Enzyme-Mediated Reactions 7.6 Introduction to Pharmacology For referencing this work, please click here. This text is published under creative commons licensing. CH103 – Chapter 7: Chemical Reactions in Biological Systems