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.
7 Key excerpts on "Amino Acids"
eBook - ePubBiochemistry
An Organic Chemistry Approach
- Michael B. Smith(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...11 Amino Acids There is an important class of difunctional molecule that is critical to an understanding of biological processes. Amino Acids comprise the backbone of peptides, and thereby of enzymes. This chapter will discuss the structure, nomenclature, and characteristics of Amino Acids. 11.1 Characteristics of Amino Acids An amino acid, as the name implies, has one amine unit (–NR 2) and one carboxylic acid unit (a carboxyl group, COOH). The nomenclature for a generic amino acid is dominated by the carboxyl, so the parent name is “acid” and the NR 2 unit is treated as a substituent. When an amine unit is a substituent the name “amino” is used, so these compounds are amino carboxylic acids, or just Amino Acids. Amino Acids are easily named using IUPAC nomenclature and the carboxylic acid is the parent for each new compound. Two examples are 2-aminopropanoic acid (known as alanine) and 5-amino-3,5-dimethylheptanoic acid. There are a variety of structural variations for Amino Acids. If the amine unit is attached to C2, the α-carbon of the carboxylic acid chain, the compound is an α-amino acid. If the amine group is on C3, the β-carbon it is a β-amino acid. Similarly, there are γ-Amino Acids, δ-Amino Acids, and so on. Due to their biological importance, α-Amino Acids will be discussed most of the time. The common names of α-Amino Acids are presented in Table 11.1 in Section 11.2. To distinguish α-Amino Acids from other Amino Acids, the term non-α-Amino Acids is used. 5-Amino-3,5-dimethylheptanoic acid is a non-α-amino acid, for example. Table 11.1 Structures, Names, Three-Letter Code and One-Letter Code of the 20 Essential Amino Acids, Based on the Structure in Figure 11.5 R Name Three-Letter Code One-Letter...
eBook - ePubBiochemistry Explained
A Practical Guide to Learning Biochemistry
- Thomas Millar(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...4 Amino Acids and their Functions In this chapter you will learn: the functional groups: an amine and carboxyl groups to understand the general structure of amino acid the structures, names and single letter symbols for the 20 Amino Acids found in proteins how 2 cysteines may be oxidised to form the bridging amino acid cystine how the carbons of Amino Acids are named or numbered the terms ampholyte and zwitterion and how these relate to Amino Acids the structure of an amide bond and the special case a peptide bond special functions of Amino Acids (e.g. neurotransmitters) and structural relationships between Amino Acids how ketones are formed from Amino Acids by removing ammonia from the αC the synthesis of the bioactive amines dopamine, noradrenaline, adrenaline and serotonin. to understand the basis for Parkinson’s disease and phenylketonuria that tyrosine, serine and threonine are phosphorylation sites in proteins the importance of decarboxylation in the formation of some active amines such as histamine how sugars may attach to the Amino Acids serine, threonine and asparagine Basic structure and nomencalture of Amino Acids The name amino acid suggests that these structures have an amine and an acid group. Indeed this is true; Amino Acids have an amino group and a carboxylic acid. The structure of a typical L-amino acid is illustrated below. This type of amino acid is the basis of proteins. Q&A 1 : Draw the chemical structures of a carboxylic acid, and an amine group. There is a central carbon that has bonds to an amine group, a carboxylic acid, an hydrogen and a variable R group. Since this central carbon has 4 different groups attached to it, it is a chiral carbon and hence there are 2 possible isomers, L and D. Nearly all Amino Acids in biochemistry are of the L-form (L for life). Note that this is the opposite of sugars, which nearly always occur as the D isomer. You need to learn their structure in this orientation...
eBook - ePub- David P. Clark(Author)
- 2009(Publication Date)
- Academic Cell(Publisher)
...All have a central carbon atom, the alpha carbon, surrounded by a hydrogen atom, an amino group (NH 2), a carboxyl group (COOH), and a variable side chain, the R-group (Fig. 3.24). Amino Acids are joined together by peptide bonds (Fig. 3.25). The first amino acid in the chain retains its free amino group and this end is often called the amino - or N-terminus of the polypeptide chain. The last amino acid to be added is left with a free carboxyl group and this end is often called the carboxy - or C-terminus. Figure 3.24 General Features of Amino Acids Almost all Amino Acids found in proteins have the features shown in common. In glycine, the simplest amino acid, the R group is a single hydrogen atom. In proline, the R group consists of a ring structure that bonds to the nitrogen atom shown. This therefore only has a single attached hydrogen and becomes an imino group (—NH—). Figure 3.25 Formation of a Polypeptide Chain A polypeptide chain is formed as amino and carboxyl groups on two neighboring Amino Acids combine and eliminate water. The linkage formed is known as a peptide bond. No matter how many Amino Acids are added, the growing chain always has an N- or amino terminus, and a C- or carboxy terminus. alpha carbon The central carbon atom of an amino acid, to which the amino, carboxyl and R groups are attached enzyme A protein or RNA molecule that catalyses a chemical reaction peptide bond Type of chemical linkage holding Amino Acids together in a protein molecule polypeptide chain Polymeric chain of Amino Acids R-group Chemical group forming side chain of amino acid Some proteins consist of a single polypeptide chain; others contain more than one. To function properly, many proteins need extra components, called cofactors or prosthetic groups, which are not made of Amino Acids...
eBook - ePub- Guoyao Wu(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
...4 Chemistry of Protein and Amino Acids The word “protein” originated from the Greek word “proteios,” meaning prime or primary (Meister 1965). A protein is a large polymer of Amino Acids (AAs) linked via the peptide bond (–CO–NH–). Different proteins have different chemical properties (e.g., AA sequences, molecular weights, ionic charges, three-dimensional (3D) structures, hydrophobicity, and function). The general structure of an AA is shown in Figure 4.1. There may be one or more polypeptide chains in a protein, which contains its constituents (nitrogen, carbon, oxygen, hydrogen, and sulfur atoms). A protein may be covalently bonded to other atoms and molecules (e.g., phosphates) and non-covalently attached with minerals (e.g., calcium, iron, copper, zinc, magnesium, and manganese), certain vitamins (e.g., vitamin B 6, vitamin B 12, and lipid-soluble vitamins), and/or lipids. Protein is the major nitrogenous macronutrient in foods and the fundamental component of animal tissues (Wu 2016). It has structural, signaling, and physiological functions in animals (Table 4.1). Figure 4.1 Fisher projections for configurations of AAs relative to l - and d -glyceraldehydes. The general structure of an AA in the non-ionized form is shown...
eBook - ePub- Raymond S. Ochs(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
...5 Amino Acids and Proteins The word protein is of Greek origin, meaning “first place” or primary. Berzelius originated this term in 1838 to identify a substance found in plant fibers essential for animal nutrition. This identification was well before the molecular nature of proteins was discovered. Proteins are the most diverse of biomolecules. They include structural proteins (such as the plant fibers), binding proteins (such as hemoglobin), and enzymes (such as sucrase). In this chapter, we examine protein structure and some elements of their binding behavior. In the next, we examine their function as enzymes. The proteins also play a central role in all subsequent chapters of the book, commensurate with their paramount importance in biochemistry. 5.1 Common Structure of the Amino Acids All Amino Acids contain an amine group (most commonly a primary amine) and a carboxyl group (the acid portion) attached to the same carbon. The latter is called the α-carbon, from an organic chemistry nomenclature system that assigns Greek letters to carbons adjacent to carboxyl groups: α, β, etc (Figure 5.1). Note that this is a distinctive use of the Greek lettering system from the carbohydrates. Also bound to the α-carbon is a hydrogen atom (the α-hydrogen) and a variable group designated as R (Figure 5.2). Twenty different R groups make up the common Amino Acids, meaning those incorporated into proteins. Except for glycine (for which R is a hydrogen atom), the α-carbon is chiral and designated as l or d by comparison to the reference molecule glyceraldehyde, illustrated in Figure 5.3 for the case of alanine (in which R is –CH 3). The carboxyl group of alanine is most similar to the carbonyl group of glyceraldehyde. The amine group of alanine is most similar to the OH group of glyceraldehyde. In nature, virtually all Amino Acids are present in the l form. FIGURE 5.1 Organic carboxyl bearing chain numbering...
eBook - ePub- S. P. Bhutani(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
...Even in plants, where carbohydrates are more abundant as structural materials, proteins are present in those parts that are responsible for growth and reproduction. The fundamental structure of proteins is simple. Proteins are biopolymers of α-Amino Acids. They consist of long chains of α-Amino Acids bonded to each other by amide bonds also known as peptide linkages between the carboyxlic group of one amino acid with the amino group of another. Thus, proteins are high molecular weight polypeptides. Their molecular weight may range from 5000–100,000 units. A single protein molecule contains hundreds or even thousands of amino acid units. About twenty different Amino Acids are the building blocks of proteins. The number of different combinations, that is the number of different protein molecules that are possible, is almost infinite. 2.2 Amino Acids – THE BUILDING BLOCKS OF PROTEINS We have seen above that α-Amino Acids are the building blocks of proteins. Hydrolysis of proteins with an acid or base yields a mixture of different Amino Acids. Naturally occurring proteins on hydrolysis may yield twenty-two different Amino Acids. These Amino Acids have an important structural feature in common. All are α-Amino Acids; i.e., the amino group is bonded to the α-carbon atom next to the carboxyl group. The simplest amino acid is glycine. All others can be derived from glycine. where the R group is different for different Amino Acids. With the exception of glycine, all naturally occurring Amino Acids have the L -configuration at the α-carbon. That means they have the same relative configuration as L -glyceraldehyde. As the two functional groups present in Amino Acids are acidic and basic, all Amino Acids are amphoteric and actually exist as zwitterions...
eBook - ePub- Raja Sivamani, Jared R. Jagdeo, Peter Elsner, Howard I. Maibach, Raja Sivamani, Jared R. Jagdeo, Peter Elsner, Howard I. Maibach(Authors)
- 2015(Publication Date)
- CRC Press(Publisher)
...Chapter 15 Amino Acids and Derivatives Kazutami Sakamoto Introduction Amino Acids are molecules with both an amino group and carboxylic group. There are 20 kinds of naturally occurring Amino Acids with optical active structures at α-position (L-Amino Acids) except glycine. Greenstein and Winitz said: “Few products of natural origin are versatile in their behavior and properties as are the Amino Acids, and few have such a variety of biological duties to perform” in their preface of Chemistry of the Amino Acid in 1961. 1 Subsequently significant progress has been made on the knowledge of Amino Acids, and technical achievements to utilize such progress are remarkable, including cosmetic and cosmeceutical applications. This is due to the market growth and cost reduction of certain Amino Acids for many industrial applications. For example, in food applications there is huge and still growing consumption generated for glutamic acid (Glu) and glycine (Gly) as food additives and aspartic acid (Asp) and phenylalanine (Phe) as raw materials for the artificial sweetener “aspartame.” Consumption of lysine (Lys), methionine (Met), and threonine (Thr) is expanding in the animal food additives market. Cysteine (CysH) and proline (Pro) are major Amino Acids utilized in the flavor industry to manufacture natural flavors by Maillard reaction with sugars. Health food and pharmaceutical intermediates are other rapidly growing markets for many Amino Acids...
