Textbook Question
What is the difference in hydrogen bonding between an α helix and a β−pleated sheet?
Ch.16 Amino Acids, Proteins, and Enzymes
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353
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Table of contents
- Ch.1 Chemistry in Our Lives11
- Ch.2 Chemistry and Measurements80
- Ch.3 Matter and Energy54
- Ch.4 Atoms and Elements51
- Ch.5 Nuclear Chemistry42
- Ch.6 Ionic and Molecular Compounds57
- Ch.7 Chemical Quantities and Reactions41
- Ch.8 Gases29
- Ch.9 Solutions51
- Ch.10 Acids and Bases and Equilibrium65
- Ch.11 Introduction to Organic Chemistry: Hydrocarbons78
- Ch.12 Alcohols, Thiols, Ethers, Aldehydes, and Ketones83
- Ch.13 Carbohydrates54
- Ch.14 Carboxylic Acids, Esters, Amines, and Amides90
- Ch.15 Lipids61
- Ch.16 Amino Acids, Proteins, and Enzymes84
- Ch.17 Nucleic Acids and Protein Synthesis83
- Ch.18 Metabolic Pathways and ATP Production67
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook
Chapter 16, Problem 22d
What type of interaction would you expect between the R groups of the following amino acids in a quaternary structure?
d. alanine and proline
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Identify the R groups of the amino acids alanine and proline. Alanine has a nonpolar methyl group (-CH₃) as its R group, while proline has a nonpolar cyclic structure (a pyrrolidine ring) as its R group.
Recognize that both alanine and proline have nonpolar R groups. Nonpolar groups tend to interact through hydrophobic interactions in a protein's quaternary structure.
Understand that hydrophobic interactions occur when nonpolar groups cluster together to avoid contact with water, stabilizing the protein's structure.
Conclude that the interaction between the R groups of alanine and proline in a quaternary structure would primarily involve hydrophobic interactions.
Note that these interactions contribute to the overall stability of the protein's quaternary structure by minimizing the exposure of nonpolar groups to the aqueous environment.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Quaternary Structure of Proteins
Quaternary structure refers to the complex formation of multiple polypeptide chains (subunits) that come together to form a functional protein. This level of structure is stabilized by various interactions between the R groups of the amino acids in the subunits, which can include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals forces.
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Quaternary Protein Structure Concept 1
R Groups of Amino Acids
The R group, or side chain, of an amino acid determines its unique properties and interactions. In the case of alanine, which has a nonpolar, hydrophobic side chain, and proline, which has a unique cyclic structure that introduces rigidity, their interactions in a quaternary structure can influence the overall stability and conformation of the protein.
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Hydrophobic and Hydrophilic Interactions
Hydrophobic interactions occur when nonpolar R groups, like that of alanine, cluster together to avoid contact with water, while hydrophilic interactions involve polar or charged R groups that can form hydrogen bonds with water. In a quaternary structure, the arrangement of these interactions is crucial for maintaining the protein's stability and functionality, influencing how alanine and proline interact.
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Related Practice
Textbook Question
What type of interaction would you expect between the R groups of the following amino acids in a tertiary structure?
c. serine and aspartate
Textbook Question
What type of interaction would you expect between the R groups of the following amino acids in a quaternary structure?
a. phenylalanine and isoleucine
Textbook Question
A portion of a polypeptide chain contains the following sequence of amino acids:
—Leu—Val—Cys—Asp—
a. Which amino acids are likely to be found on the inside of the protein structure? Why?
Textbook Question
A portion of a polypeptide chain contains the following sequence of amino acids:
—Leu—Val—Cys—Asp—
c. How does the primary structure of a protein affect its tertiary structure?
Textbook Question
In myoglobin, about one-half of the 153 amino acids have nonpolar R groups.
a. Where would you expect those amino acids to be located in the tertiary structure?