Bioenergetics and Introduction to Metabolism PDF

BIOENERGETICS AND INTRODUCTION INTO METABOLISM  An Overview Reactions in multistep sequences are called pathways. In a pathway, the product of one reaction serves as the substrate of the subsequent reaction. Different pathways can also intersect, forming an integrated a...

BIOENERGETICS AND INTRODUCTION INTO METABOLISM  An Overview Reactions in multistep sequences are called pathways. In a pathway, the product of one reaction serves as the substrate of the subsequent reaction. Different pathways can also intersect, forming an integrated and purposeful network of chemical reactions. These are collectively called metabolism.  An Overview Metabolism is a sum of chemical changes that convert nutrients into energy and finally to complex finished products of cells (The process through which organisms acquire and utilize energy for their function). Why do living organisms require a continual input of free energy? 1. Performance of mechanical work in muscle contraction and cellular movements. 2. Active transport of molecules and ions. 3. Synthesis of macromolecules and other biomolecules from simple precursors.  An Overview  Metabolism consists of catabolism and anabolism  Catabolism: degradative pathways  Usually energy- yielding!  Anabolism: biosynthetic pathways  energy-requiring!  Catabolic pathways deliver chemical energy in the form of ATP, NADH, NADPH, and FADH2. These energy carriers are used in anabolic pathways to convert small precursor molecules into cell macromolecules.  Catabolism  Catabolism is the degradative phase of metabolism in which organic nutrient molecules (carbohydrates, fats, and proteins) are converted into smaller, simpler end products (such as lactic acid, CO2, NH3).  Catabolic pathways release energy, some of which is conserved in the formation of ATP and reduced electron carriers (NADH, NADPH, and FADH2); the rest is lost as heat. The Stages of Catabolism Note: In stage 2 some energy is captured as ATP, but the amount is small compare d with the energy produced during stage 3 of catabolism. The tricarboxylic acid (TCA ) cycle is the final common pathway in the oxidation of fuel molecules such as acetyl CoA. Large amounts of AT P are generated as electrons, which flow from NADH and FADH2 to oxygen via oxidative phosphorylation. Anabolic Pathways  In anabolism, also called biosynthesis, small, simple precursors are built up into larger and more complex molecules, including lipids, polysaccharides, proteins, and nucleic acids.  Anabolic reactions require an input of energy, generally in the form of the phosphoryl group transfer potential of ATP and the reducing power of NADH, NADPH, and FMDH2.  In general, catabolic pathways are convergent and anabolic pathways divergent One starting component of the pathway is regenerated in a series of reactions