Chemistry
Amino Acids
Amino acids are organic compounds that serve as the building blocks of proteins. They contain an amine group, a carboxylic acid group, and a side chain that varies among different amino acids. There are 20 standard amino acids that are commonly found in proteins, each with its own unique chemical structure and properties.
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10 Key excerpts on "Amino Acids"
eBook - PDFPolysaccharides Peptides and Proteins
Pharmaceutical Monographs
- R. T. Coutts, G. A. Smail, J. B. Stenlake(Authors)
- 2014(Publication Date)
- Butterworth-Heinemann(Publisher)
To the organic chemist an amino acid refers to any molecule possessing both an amino and an acid group. The bio-chemist, on the other hand, tends to reserve the term for those compounds in which an amino group occurs on the same carbon atom as a carboxyl group—α-Amino Acids (I)—and which have largely been isolated from protein hydrolysates. H H I I R—C—COOH R—C—COO~ I I NH 2 NH 3 (I) + da) 80 Amino Acids The side group (R in I) in most cases is neutral and thus the amino acid is neutral since under most conditions it is the salt-like dipolarionic form (la) which is favoured. A few Amino Acids con-tain a second acidic or basic function in the side-chain and the molecule as a whole then departs from neutrality. Table 2 illus-trates the common Amino Acids of which proteins are largely com-posed, whereas Table 3 shows Amino Acids which are of less com-mon occurrence and are not all derived from proteins. In general the salt-like nature of the Amino Acids confers on them characteris-tic non-volatility, classical insolubility in organic solvents and high indefinite melting points which are almost invariably accom-panied by decomposition. The condensation of the amino group of one amino acid with the carboxyl group of another and the elimination of water results in the formation of a peptide linkage (—CONH—). Two or more Amino Acids joined by this linkage represents a peptide, and the prefixes di-, tri-, tetra-, etc. indicate the number of constituent Amino Acids. The term oligo-peptide is sometimes used to refer generally to these smaller peptides. The term polypeptide can be used to designate all but the simplest peptides. The proteins con-stitute the largest group of anhydrocopolymers of Amino Acids. An arbitrary distinction is usually drawn between polypeptides and proteins on a basis of molecular weight. The term polypeptide is usually reserved for those molecules whose molecular weight is less than 10,000.
eBook - ePub- Donald Voet, Judith G. Voet(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
Chapter 3 Amino Acids1 The Amino Acids of ProteinsA. General PropertiesB. Peptide BondsC. Nomenclature of Amino AcidsD. Classification and Characteristics2 Stereochemistry of Amino AcidsA. An Operational ClassificationB. The Fischer ConventionC. The Cahn–Ingold–Prelog SystemD. Chirality and Biochemistry3 Chemical Properties of Amino AcidsA. Acid–Base PropertiesB. Reactions of Amino Acids4 “Nonstandard” Amino AcidsA. Amino Acid Derivatives in ProteinsB. Specialized Roles of Amino AcidsIt is hardly surprising that much of the early biochemical research was concerned with the study of proteins. Proteins form the class of biological macromolecules that have the most well-defined physicochemical properties, and consequently they were generally easier to isolate and characterize than nucleic acids, polysaccharides, or lipids. Furthermore, proteins, particularly in the form of enzymes, have obvious biochemical functions. The central role that proteins play in biological processes has therefore been recognized since the earliest days of biochemistry. In contrast, the task of nucleic acids in the transmission and expression of genetic information was not realized until the late 1940s and their catalytic function only began to come to light in the 1980s, the role of lipids in biological membranes was not appreciated until the 1960s, and the biological functions of polysaccharides are still somewhat mysterious.In this chapter we study the structures and properties of the monomeric units of proteins, the Amino Acids. It is from these substances that proteins are synthesized through processes that we discuss in Chapter 27 . Amino Acids are also energy metabolites and, in animals, many of them are essential nutrients (Chapter 23
eBook - PDF- William H. Brown, Thomas Poon(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
595 WE BEGIN THIS CHAPTER with a study of Amino Acids, the building blocks of the biological macromolecules known as proteins, and compounds whose chemistry is built on two familiar classes of compounds, the amines (Chapter 10) and carboxylic acids (Chapter 13). We will learn that the physical and acid–base properties of Amino Acids are crucial in deter- mining the structures of proteins, which in turn determine their many functions in living organisms. 18.1 What Are the Many Functions of Proteins? Proteins are among the most important of all biological compounds. Among the functions performed by these vital molecules are the following: ● Structure —Structural proteins such as collagen and keratin are the chief constituents of skin, bones, hair, and nails. ● Catalysis —Virtually all reactions that take place in living systems are catalyzed by a spe- cial group of proteins called enzymes. Without enzymes, these many reactions would take place so slowly as to be useless. 18 Amino Acids and Proteins K E Y Q U E S T I O N S 18.1 What Are the Many Functions of Proteins? 18.2 What Are Amino Acids? 18.3 What Are the Acid–Base Properties of Amino Acids? 18.4 What Are Polypeptides and Proteins? 18.5 What Is the Primary Structure of a Polypeptide or Protein? 18.6 What Are the Three‐Dimensional Shapes of Polypeptides and Proteins? H O W TO 18.1 Approximate the Charge of an Amino Acid at Any Given pH C H E M I C A L C O N N E C T I O N S 18A Spider Silk: A Chemical and Engineering Wonder of Nature 18 © gabrielaschaufelberger/iStockphoto Spider silk is a fibrous protein that exhibits unmatched strength and toughness. Inset: Models of D‐alanine and glycine, the major components of the fibrous protein of silk. 596 C H A P T E R 1 8 Amino Acids and Proteins ● Movement —Muscle expansion and contraction are involved in every movement we make. Muscle fibers are made of proteins called myosin and actin. ● Transport —A large number of proteins perform transport duties.
eBook - PDF- Allan Blackman, Steven E. Bottle, Siegbert Schmid, Mauro Mocerino, Uta Wille(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
CHAPTER 24 Amino Acids, peptides and proteins LEARNING OBJECTIVES After studying this chapter, you should be able to: 24.1 define the structure of Amino Acids 24.2 control the charge present on Amino Acids using pH 24.3 describe the linking of Amino Acids together to make peptides and proteins 24.4 categorise protein structures as 1°, 2°, 3° or 4° 24.5 explain the functional importance of the three-dimensional shape of proteins 24.6 exploit chemical and physical processes to change protein properties. Amino Acids are molecules that contain both an amine functional group (described in the chapter on alcohols, amines and related compounds) and a carboxylic acid functional group (described in the chapter on carboxylic acids). Amino Acids are important in their own right, but they are also critically important for life as they provide the building blocks of peptides and proteins. In this chapter we will look at the acid– base properties of Amino Acids, as these control much of the nature of peptides and proteins. Understanding the chemistry of Amino Acids allows us in turn to understand the more complex structures and properties of peptides and proteins. Proteins are among the most important of all biological compounds as they are integrally important in the vital functions of: • movement: muscle fibres are made of proteins called myosin and actin • catalysis: virtually all 1that take place in living systems are catalysed by a special group of proteins called enzymes • structure: structural proteins such as collagen and keratin are the chief constituents of skin, bones, hair and fingernails • transport: the protein haemoglobin is responsible for the transport of oxygen from the lungs to tissues, while other proteins transport molecules across cell membranes • protection: a group of proteins called antibodies represent one of the body’s major defences against disease. Peptides are a major component of the supplements and health food sector.
- Rifat Latifi, Stanley J. Dudrick(Authors)
- 2003(Publication Date)
- CRC Press(Publisher)
C hapter З Biochemistry of Amino Acids: Clinical Implications Rifat Latifi , Khawaja Aizimuddin Introduction Ajnino acids, as organic compounds, containing both an amino group and a carboxylic acid group, are the monomeric and basic constituents of all proteins. Amino Acids occurring in protein are known as alpha-Amino Acids and have one or two empirical formulae RCH (NH+)COOH' or R-CH-(NH3)COO Beta-Amino Acids and gamma-Amino Acids also occur in nature but are not components of pro teins, and their significance is not known. This chapter reviews the basic biochemis try and physiology of Amino Acids and their functions as fundamental units of proteins. Their increasingly recognized and valued role in the metabolic and nutritional man agement of critically ill patients will be discussed through out this volume. Structure of Amino Acid and Proteins A protein molecule consists of Amino Acids held together by peptide bonds, which form a long polypeptide chain. The exact sequence of Amino Acids in the chain, referred to as the primary structure of the protein, is determined genetically and defines how the chain is folded into more complex conformations or shapes. A polypeptide, which is folded into a helical or pleated sheet configuration, is referred to as a secondary structure. If the sequence of Amino Acids is then folded into a three-dimensional configuration, a tertiary structure is created. Some pro teins have a higher level of molecular architecture known as the quaternary struc ture, in which several chains aggregate and function as a unit. The amino acid sequence and protein structure determine the nature and function of protein molecules upon which virtually every process of life depends. The folding of polypeptide chains into alpha helix and beta pleated sheets has clinical implications. The alpha helix is a rod-like structure and contains a tightly coiled polypeptide main chain.
eBook - PDF- BIOTOL, B C Currell, R C E Dam-Mieras(Authors)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
In this chapter we will examine the structure and properties of these building blocks before examining proteins in the next chapter. We will particularly focus on their ionisation behaviour as this is vitally important if we are to understand the properties of both Amino Acids and proteins. Amino Acids 17 Enzymes Immune/protective proteins Transport proteins Storage proteins Structural proteins Contractile/motile proteins Hormones and their receptors Regulating proteins The catalysts of biochemical reactions Antibodies: recognise and bind to foreign substances Complement: complexes with some antibody -antigen complexes and causes destruction of pathogens Fibrinogen and thrombin: involved in blood clotting Serum albumin - transport of fatty acids Haemoglobin - transport of oxygen Ceruloplasmin or transferrin - transport of iron Ovalbumin - in egg white Casein - in milk Ferritin - storage of iron Storage proteins in seeds eg beans Collagen - in skin Elastin - in elastic tissues Keratin - in hair and nails Viral coat proteins Membrane structural proteins Myosin, actin - involved in movement Insulin, growth hormone. Receptors for signal reception and for transport of material into cells Selective stimulation or inhibition of expression of DNA Table 2.1 The roles of proteins. 2.2 Amino Acids ammo groups carboxyl groups a carbon atom All proteins are composed of compounds called Amino Acids, which are frequently thought of as the building blocks of proteins. Amino Acids consist of at least one amino group (-NH 2 ), and at least one carboxyl group (-COOH). Whilst an enormous number of Amino Acids probably exist, those which are incorporated into proteins are all of a type called -Amino Acids. Routinely, only 20 different -Amino Acids are found in proteins. An -amino acid is one in which both an amino group and a carboxyl group are joined to the same carbon atom, which is known as the -carbon atom (Figure 2.1).
eBook - PDFHandbook of Food Analysis
Volume 1: Physical Characterization and Nutrient Analysis
- Leo M.L. Nollet(Author)
- 2004(Publication Date)
- CRC Press(Publisher)
The molecular mass and structure of all these Amino Acids are compiled in Tables 1 , 2 , and 3 . All Amino Acids, except proline, contain one primary amino group (-NH 2 ) in the position in relation to the carboxy group (-COOH). Each amino acid has a characteristic side chain (R group), which has a strong influence on its physicochemical properties. So, Amino Acids are usually grouped according to the polarity of this group (nonpolar or hydrophobic side chains, polar or hydro-philic side chains, positively or negatively charged groups). The stereochemical L isomer is the most usual form in nature and, in practice, all Amino Acids found in hydrolyzates from animal and vegetable proteins are isomers of the L form. The D isomers may be found in some specific cases like in the cell walls of certain microorganisms and polypeptides with antibiotic action. II. WHY ANALYZE FOR AMINO ACID CONTENT? A. Nutritional Purposes Amino Acids constitute essential components in the living cell, being necessary either in their free form or forming part of proteins. Amino Acids are generally supplied in foods and/or may be synthesized through different metabolic pathways from other Amino Acids inside the organism. As mentioned above, some of these Amino Acids, known as essential Amino Acids, cannot be synthesized in the organism and must be supplied in the diet. In addition, some Amino Acids are essential at certain ages, like infancy, or in total parenteral nutrition. The importance of amino acid analysis, in order to obtain a good knowledge of the 83 amino acid composition of a particular protein, food, or diet, is thus evident. Furthermore, the knowledge of a limiting amino acid is also very important in basic foods or when designing foods for populations with specific dietary needs such as the elderly or infants. Accurate compositional data for all the Amino Acids is essential for assessing the nutritional quality of infant formulas.
eBook - PDFBiochemistry
An Integrative Approach
- John T. Tansey(Author)
- 2019(Publication Date)
- Wiley(Publisher)
nanantachoke/ShutterStock Just as these building materials are used in constructing office buildings, Amino Acids are the building blocks of proteins. CHAPTER 3 Proteins I An Introduction to Protein Structure and Function Proteins in Context Throughout history advances in materials have changed tools and how we make them. Ancient civilizations may have used clay pots or made weapons of bronze or iron. In modern times refined alloys of aluminum have been used in applications ranging from cans to aircraft. Perhaps people in the future will mark our current era by the use of plastics or silicon microchips. In biochemistry, we consider proteins to be a wonder material used in thousands of applications. Proteins are polymers of Amino Acids which have evolved to have numerous distinct functions: they can be structural or catalytic, transmit information, help protect an organism by binding to foreign molecules, provide motility, store Amino Acids, or transport molecules within the cell or the organism. This chapter begins by discussing Amino Acids, the building blocks of proteins, then moves on to the basics of protein structure and a brief description of how these macromolecules fold into their specific confor- mations. The chapter ends by examining several different examples of different proteins. These aspects of protein chemistry are discussed in Dynamic Figure 3.1. CHAPTER OUTLINE 3.1 Amino Acid Chemistry 3.2 Proteins Are Polymers of Amino Acids 3.3 Proteins Are Molecules of Defined Shape and Structure 3.4 Examples of Protein Structures and Functions 67 68 CHAPTER 3 Proteins I COMMON THEMES Evolution’s outcomes are conserved. • Mutations to DNA sequences may result in alterations to a protein’s amino acid sequence. The new protein may function normally, have a new and slightly altered function, or be completely nonfunctional. • The amino acid sequence of proteins can help establish the evolutionary relationship between organisms.
eBook - ePub- (Author)
- 2014(Publication Date)
- Wiley-VCH(Publisher)
Amino Acids Karlheinz Drauz, Degussa AG, Hanau-Wolfgang, Germany Ian Grayson, Degussa, Middlesbrough, United Kingdom Axel Kleemann, Hanau, Germany Hans-Peter Krimmer, Degussa AG, Hanau-Wolfgang, Germany Wolfgang Leuchtenberger, Degussa AG, Düsseldorf, Germany Christoph Weckbecker, Degussa AG, Hanau-Wolfgang, Germany1. Introduction and History
The proteins, although they occur in an almost infinite variety, are composed of a relatively small number of basic building blocks, all α-Amino Acids. In addition, the Amino Acids fulfill certain regulatory functions in the metabolism and are required for the biosynthesis of other functional structures. This review is limited, for the most part, to the protein-forming Amino Acids, because they are by far the most widely distributed in nature and are of considerable economic interest.The ca. 20 different α-Amino Acids found in proteins are simple organic compounds, in which an amino group and a side chain (R) are attached alpha to the carboxyl function. The R group may be aliphatic, aromatic, or heterocyclic and may possess further functionality.Amino acid Dipeptide Protein (n > 50) At present over 200 naturally occurring α-Amino Acids are known [1–7]. Table 1 shows the α-Amino Acids found in proteins, where they occur exclusively as the l-enantiomers. d-Amino Acids have been found only in the cell walls of some bacteria, in peptide antibiotics, and in the cell pools of some plants [10, 14, 15]. The l-Amino Acids are commonly abbreviated with three-letter or one-letter codes, as shown in Table 1
eBook - PDF- H. Stephen Stoker(Author)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
Under proper conditions, Amino Acids can bond together to produce an unbranched chain of Amino Acids. The length of the amino acid chain can vary from a few Amino Acids to many Amino Acids. Representative of such chains is the following five-amino-acid chain. Amino acid ! Amino acid ! Amino acid ! Amino acid ! Amino acid Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 366 CHAPTER 9 Proteins Such a chain of covalently linked Amino Acids is called a peptide. A peptide is an unbranched chain of Amino Acids. Peptides are further classified by the number of Amino Acids present in the chain. A compound containing two Amino Acids is spe-cifically called a dipeptide; three Amino Acids joined together in a chain constitute a tripeptide; and so on. The name oligopeptide is loosely used to refer to peptides with 10 to 20 amino acid residues, and the name polypeptide is used to refer to longer peptides. A polypeptide is a long unbranched chain of Amino Acids. Nature of the Peptide Bond The bonds that link Amino Acids together in a peptide chain are called peptide bonds. There are four peptide bonds present in a pentapeptide. The nature of the peptide bond becomes apparent by reconsidering a chemical reaction previously encountered. In Section 6-16, the reaction between a carboxylic acid and an amine to produce an amide was considered.
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