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Amino acids are organic compounds that serve as the building blocks of proteins. They play a crucial role in various biological processes. Here are some key points about amino acids: Basic Structure: Each amino acid consists of a central carbon atom (the alpha carbon), an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a distinctive side chain (R-group) that varies between different amino acids. Types of Amino Acids: There are 20 standard amino acids commonly found in proteins. These are alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. Essential Amino Acids: Of the 20 standard amino acids, nine are termed essential for humans because they cannot be synthesized by the body and must be obtained from the diet. These include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Roles in the Body: Amino acids are involved in various metabolic processes. They are the building blocks of proteins, which are crucial for body functions like cell structure, transport, enzyme activity, and as precursors for neurotransmitters and hormones. Protein Synthesis: During protein synthesis, amino acids are linked together by peptide bonds, forming long chains that fold into specific three-dimensional structures, which determine the function of the protein. Dietary Sources: Amino acids are obtained from protein-rich foods such as meat, fish, dairy products, eggs, and plant sources like legumes, nuts, and grains. Supplements and Medicine: Certain amino acids are used in dietary supplements and medications due to their role in muscle growth, immune function, and neurotransmitter regulation. Biochemical Properties: Amino acids can be classified based on the properties of their side chains, such as nonpolar, polar, acidic, and basic. This classification influences how amino acids interact with each other and with their environment, affecting protein structure and function. Understanding amino acids is essential in fields like biochemistry, nutrition, and medicine due to their fundamental role in life's processes. Problem: A polypeptide with a net positive charge at physiological pH (~7.4) most likely contains amino acids with R groups of what type? А) Acidic R groups В) Aromatic R groups С) Aliphatic R groups D) Basic R groups *
