voet 01 - 1 Introduction to the Chemistry of Life This...

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1 Introduction to the Chemistry of Life This chapter introduces you to life at the biochemical and cellular level. It begins with a discussion of the chemical origins of life and its early evolution. This discussion continues into ideas and theories about the evolution of organisms, followed by a brief introduction to taxonomy and phylogeny viewed from a molecular perspective. The chapter concludes with an introduction to the basic concepts of thermodynamics and its application to living systems. Biochemistry, like all other sciences, is a based on the measurement of observable phenomena. Hence, it is important to become familiar with the conventions used to measure energy and mass. Box 1-1 presents the essential biochemical conventions that we will encounter throughout Fundamentals of Biochemistry . Essential Concepts The Origin of Life 1. Living matter consists of a relatively small number of elements, of which C, N, O, H, Ca, P, K, and S account for ~98% of the dry weight of most organisms (which are 70% water). These elements form a variety of reactive functional groups that participate in biological structure and biochemical reactions. 2. The current model for the origin of life proposes that organisms arose from the polymerization of simple organic molecules to form more complex molecules, some of which were capable of self-replication. 3. Most polymerization reactions involving the building of small organic molecules into larger more complex ones occur by the formation of water. This is called a condensation reaction. Cellular Architecture 4. A key development in the origin of life was the formation of a membrane that could separate the critical molecules required for replication and energy capture from a potentially degradative environment. 5. Complementary surfaces of molecules and macromolecules provide a template for biological specificity (e.g., macromolecular assembly, enzyme activity, and expression and replication of the genome).
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Chapter 1 Introduction to the Chemistry of Life 2 6. Modern cells can be classified as either prokaryotic or eukaryotic. Eukaryotic cells are distinguished by a variety of membrane-bounded organelles and an extensive cytoskeleton. Organismal Evolution 7. Prokaryotes show a limited range of morphologies but very diverse metabolic capabilities. 8. Phylogenetic evidence based on comparisons of ribosomal RNA genes have been used by Woese and colleagues to group all organisms into three domains: archaea, bacteria, and eukarya. 9. The evolution of sexual reproduction marks an important step of the evolution of organisms, because it allows for genetic exchanges that lead to an increase in the adaptability of a population of organisms to changing environments. 10. Eukaryotes contain several membrane-bounded structures, such as mitochondria and chloroplasts, that may be descended from ancient symbionts.
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voet 01 - 1 Introduction to the Chemistry of Life This...

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