Textbook Question
Valine is an amino acid with a nonpolar side chain and serine is one with a polar side chain. Draw the two amino acids.
a. Why is the side chain for valine nonpolar, whereas the side chain for serine is polar?
Ch.18 Amino Acids and Proteins
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
Chapter 18, Problem 5a
Indicate whether each of the following molecules is an α-amino acid or not, and explain why.
a. 
Verified step by step guidance1
Step 1: Recall the structure of an α-amino acid. An α-amino acid contains a central carbon atom (called the α-carbon) bonded to four groups: an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a variable side chain (R group).
Step 2: Examine the structure of the molecule provided in the image. Identify the central carbon atom and check if it is bonded to the four required groups: an amino group, a carboxyl group, a hydrogen atom, and a side chain.
Step 3: Verify the position of the amino group. For the molecule to be an α-amino acid, the amino group must be attached to the α-carbon, which is the same carbon atom bonded to the carboxyl group.
Step 4: If the molecule meets all the criteria (central α-carbon bonded to the amino group, carboxyl group, hydrogen, and side chain), it is an α-amino acid. If any of these criteria are not met, it is not an α-amino acid.
Step 5: Provide a clear explanation based on your analysis of the molecule's structure, specifying whether it is an α-amino acid or not and why.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
α-Amino Acid Structure
An α-amino acid is characterized by having an amino group (-NH2) and a carboxyl group (-COOH) attached to the same carbon atom, known as the α-carbon. This structure is fundamental to the classification of amino acids, as it distinguishes them from other types of amino acids that may not have both functional groups on the same carbon.
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Amino Acid Catabolism: Amino Group Example 2
Classification of Amino Acids
Amino acids can be classified based on their side chains (R groups) into categories such as polar, nonpolar, acidic, and basic. This classification is important for understanding the properties and functions of amino acids in proteins, as the nature of the side chain influences how the amino acid interacts with other molecules.
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1:33Amino Acid Classifications Example 3
Role in Protein Synthesis
α-Amino acids are the building blocks of proteins, linked together by peptide bonds during protein synthesis. The sequence and composition of these amino acids determine the structure and function of the resulting protein, making it essential to identify whether a molecule is an α-amino acid when studying biological processes.
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Related Practice
Textbook Question
Examine the ball-and-stick model of valine below. Identify the carboxyl group, the amino group, and the R group.
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Textbook Question
Which amino acid is hydrophilic (dissolves in aqueous solutions)? Why?
a. isoleucine
b. phenylalanine
c. aspartic acid
Textbook Question
Consult Table 18.3 and draw alanine. Label the functional groups and give the three-letter abbreviation and the one-letter abbreviation. What group does the side chain fall into?
Textbook Question
Cortisol levels rise under stressful conditions. Oxytocin can induce relaxation and romantic feelings. What type of protein are cortisol and oxytocin?
Textbook Question
Using Table 18.3, name the α-amino acids that (a) contain an aromatic ring, (b) contain sulfur, (c) are alcohols, and (d) have alkyl-group side chains.