INTRODUCTION - RNA SPLICING Many of the RNA molecules in bacteria and virtually all RNA molecules in eukaryotes are processed to some degree after synthesis. Some of the most interesting molecular events in RNA metabolism occur during this post synthetic processing. Intriguingly, several of the enzymes that catalyze these reactions…
INTRODUCTION - RNA SYNTHESIS Transcription is, chemically and enzymatically, very similar to DNA replication. Both involve enzymes that synthesize a new strand of nucleic acid complementary to a DNA template strand. There are some important differences, of course; most notably, in the case of transcription, the new strand is made…
INTRODUCTION All amino acids are derived from intermediates in glycolysis, the citric acid cycle, or the pentose phosphate pathway. Nitrogen enters these biosynthetic pathways by way of glutamate and glutamine. Some pathways are simple, others are not. Ten of the amino acids are just one or several steps removed from…
INTRODUCTION - BIOSYNTHESIS OF NUCLEOTIDE Nucleotides have a variety of important functions in all cells. They are the precursors of DNA and RNA. They are essential carriers of chemical energy—a role primarily of ATP and to some extent GTP. They are components of the cofactors NAD, FAD, Sadenosylmethionine, and coenzyme…
INTRODUCTION - MECHANISM OF ENZYME CATALYSIS The enzymatic catalysis of reactions is essential to living systems. Under biologically relevant conditions, uncatalyzed reactions tend to be slow—most biological molecules are quite stable in the neutral-pH, mild-temperature, aqueous environment inside cells. Furthermore, many common chemical processes are unfavorable or unlikely in the…
INTRODUCTION - PROTEIN SYNTHESIS Proteins are the end products of most information pathways. A typical cell requires thousands of different proteins at any given moment. These must be synthesized in response to the cell’s current needs, transported (targeted) to their appropriate cellular locations, and degraded when no longer needed.An understanding…
INTRODUCTION - REGULATION OF ENZYME ACTION The activity of enzymes, often must be regulated so that they function at the proper time and place. The biological activity of enzyme is regulated in four principal ways:Allosteric control. Allosteric enzyme contain distinct regulatory sites and multiple functional sites. Regulation by small signal molecules…
CONCEPT OF FREE ENERGY AND THERMODYNAMICS PRINCIPLES Living cells and organisms must perform work to stay alive, to grow, and to reproduce. The ability to harness energy and to channel it into biological work is a fundamental property of all living organisms; it must have been acquired very early in…
INTRODUCTION CLASSIFICATION OF ENZYMES AND ENZYME KINETIC Enzymes are central to every biochemical process. Acting in organized sequences, they catalyze the hundreds of stepwise reactions that degrade nutrient molecules, conserve and transform chemical energy, and make biological macromolecules from simple precursors. The study of enzymes has immense practical importance. In…
INTRODUCTION ENERGY RICH BONDS, ENERGY TRANSDUCER, ISOMERISM AND RESONANCE A relevant reaction is one that makes use of an available substrate and converts it to a useful product. However, even a potentially relevant reaction may not occur. Some chemical transformations are too slow (have activation energies that are too high)…
INTRODUCTION PROTEIN SYNTHESIS REGULATION Of the 4,000 or so genes in the typical bacterial genome, or the 20,000 genes in the human genome, only a fraction are expressed in a cell at any given time. Some gene products are present in very large amounts: the elongation factors required for protein…
INTRODUCTION BIOSYNTHESIS OF FATTY ACID, CHOLESTROL AND MEMBRANE LIPID Lipids play a variety of cellular roles, some only recently recognized. They are the principal form of stored energy in most organisms and major constituents of cellular membranes. Specialized lipids serve as pigments (retinal, carotene), cofactors (vitamin K), detergents (bile salts),…