Biomolecules Lipids Proteins

The study of metabolism is a study of energy where does the energy to create complex biomolecules — lipids, proteins, and nucleic acids — come from Where does the energy to enable a living organism to do mechanical work come from How is energy stored in the cell and made available when and where it needs to be ... 

Lipids differ from the other classes of naturally occuning biomolecules (carbohydrates, proteins, and nucleic acids) in that they are more soluble in nonpolar to weakly polar- solvents (diethyl ether, hexane, dichloromethane) than they are in water. They include a variety of str-uctural types, a collection of which is introduced in this chapter. 

We ll see later in this chapter and again in Chapter 29 that carbonyl condensation reactions occur frequently in metabolic pathways. In fact, almost all classes of biomolecules—carbohydrates, lipids, proteins, nucleic acids, and many others—are biosynthesized through pathways that involve carbonyl condensation reactions. As with the or-substitution reaction discussed in the previous chapter, the great value of carbonyl condensations is that they are one of the few general methods for forming carbon-carbon bonds, thereby making it possible to build larger molecules from smaller precursors. We ll see how and why these reactions occur in this chapter. 

The complex cascades that comprise the inflammatory reaction are designed primarily to limit tissue damage and prevent or inhibit infection. ROMs play a critical role in both these beneficial processes. However, high level fluxes of toxic free radicals are capable of causing damage to diverse biomolecules, including lipids, proteins, DNA and carbohydrates (discussed below). 

Biophysical analysis of biomolecules like proteins, nucleic acids, or lipids utilizes intrinsic physical properties of the observed molecule itself or of an associated reporter molecule, which reflect information about structural characteristics, interactions, or reactions of the subject observed. In most cases the analysis (and the labels introduced) only interferes slightly with the interaction of interest and does not induce significant changes in the properties of the reactants. 

An inventory of known biomacromolecules is provided in Table 22.3. Many of these play essential metabolic roles in enabling growth and reproduction, such as the carbohydrates, lipids, proteins, and polynucleotides. Others are components of cell walls and exoskeletons. Some organisms, such as bacteria, plankton, plants, and lower invertebrates, synthesize biomolecules, called secondary metabolites, that are used to control ecological relationships, including predator/prey, host/symbiont, mating/spawning, and competition for food or space. 

Separating Biomolecules In studying a particular biomolecule (a protein, nucleic acid, carbohydrate, or lipid) in the laboratory, the biochemist first needs to separate it from other biomolecules in the sample—that is, to purify it. Specific purification techniques are described later in the text. However, by looking at the monomeric subunits of a biomolecule, you should have some ideas about the characteristics of the molecule that would allow you to separate it from other molecules. For example, how would you separate (a) amino acids from fatty acids and (b) nucleotides from glucose ... 

The great majority of the biomolecules used by cells are either carbohydrates, lipids, proteins, or nucleic acids. In addition, most cells need small amounts of vitamins and minerals in order to function properly. We now discuss all these categories of biomolecules. 

The types of biomolecules produced by anabolism are the same as the types found in food—carbohydrates, lipids, proteins, and nucleic acids. These products of anabolism are, if you will, the hosts own version of what the food once was. And if the host ever becomes food, anabolic reactions in the subsequent host will result in different versions of the molecules. Thus, organisms in a food chain live off one another by absorbing one another s energy via catabolic reactions and then rearranging the remaining atoms and molecules via anabolic reactions into the biomolecules they need to survive. 

Nitrosative stress occurs when the generation of RNS in a system exceeds the system s ability to eliminate them. Since ROS and RNS are generally highly reactive, they react with key organic substances such as lipids, proteins, and DNA [5]. Oxidation of these biomolecules can damage them and may be responsible to a variety of diseases. 

On the other hand, oxidative stress has also been found to induce PSl transcription, thereby promoting production of pathological levels of Af) in AD (Tamagno et al., 2008). Indeed, it has been proposed that the pathophysiology of oxidative stress is reflected in damage to tissue biomolecules, including lipids, proteins, and DNA by free radicals (Migliore and Coppede, 2009). 

VVeTJ sec numerous instances in future chapters where the chemistry of a given functional group is strongly affected by being in a ring rather than an open chain, because cyclic molecules are sr> commonly encountered in all classes of biomolecules, including proteins, lipids, carbohydrates, and nucleic adds, it s important that the effects of their cyclic structures be understood. 

We D see later in this chapter and again in Chapter 29 that carbon condensation reactions occur frequently in metabolic pathways. Almost all classes of biomolecules—carbohydrates, lipids, proteins, nucleic acids, and many others—are biosynthesized through routes that involve carbonyl condensation reactions. 

Water behaves differently in different environments. Properties of water in heterogenous systems such as living cells or food remain a field of debate. Water molecules may interact with macromolecular components and supramolecular structures of biological systems through hydrogen bonds and electrostatic interactions. Solvation of biomolecules such as lipids, proteins, nucleic acids, or saccharides resulting from these interactions determines their molecular structure and function. 

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