Textbook Question
What is the one-letter amino acid sequence formed from the following mRNA that codes for a pentapeptide that is an endorphin called Met-enkephalin?
5'AUG|UAC|GGU|GGA|UUU|AUG|UAA3'
Ch.11 Nucleic Acids Big Molecules with a Big Role
Frost4th EditionGeneral, Organic and Biological ChemistryISBN: 9780134988696
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Table of contents
- Ch.4 Introduction to Organic Compounds75
- Ch.5 Chemical Reactions19
- Ch.6 Carbohydrates Life's Sweet Molecules62
- Ch.7 States of Matter and Their Attractive Forces8
- Ch.8 Solution Chemistry Sugar and Water Do Mix4
- Ch.10 Proteins Workers of the Cell89
- Ch.11 Nucleic Acids Big Molecules with a Big Role69
- Ch.12 Food as Fuel An Overview of Metabolism65
Frost4th EditionGeneral, Organic and Biological ChemistryISBN: 9780134988696Not the one you use?Change textbook
Chapter 7, Problem 76b
In sickle-cell anemia, a base substitution in the hemoglobin gene replaces glutamate (a polar amino acid) with valine. Why does the replacement of one amino acid cause such a drastic change in biological function?
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Understand the concept of amino acids and their properties: Amino acids are the building blocks of proteins, and their side chains (R groups) determine their chemical properties, such as polarity, charge, and hydrophobicity. Glutamate is polar and negatively charged, while valine is nonpolar and hydrophobic.
Recognize the importance of protein structure: Proteins have specific three-dimensional structures that are determined by the sequence and properties of amino acids. The substitution of glutamate with valine alters the chemical environment and interactions within the hemoglobin protein.
Explain the impact of polarity and hydrophobicity: Glutamate's polar nature allows it to interact with water and other polar molecules, maintaining the solubility and proper folding of hemoglobin. Valine, being nonpolar, disrupts these interactions, leading to aggregation of hemoglobin molecules.
Describe the biological consequences: The aggregation of hemoglobin molecules causes the red blood cells to deform into a sickle shape, reducing their ability to transport oxygen efficiently and leading to blockages in blood vessels.
Connect the molecular change to the disease: The single amino acid substitution drastically alters the hemoglobin's function and structure, demonstrating how even small genetic mutations can have significant effects on biological systems and health.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Amino Acids and Their Properties
Amino acids are the building blocks of proteins, each with unique properties based on their side chains. Glutamate is a polar amino acid, which means it can interact well with water, while valine is non-polar and hydrophobic. This difference in polarity affects how proteins fold and function, as the environment around them influences their structure.
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Protein Structure and Function
Proteins have four levels of structure: primary, secondary, tertiary, and quaternary. The primary structure is the sequence of amino acids, which determines the protein's overall shape and function. A single amino acid substitution, like glutamate to valine, can disrupt the protein's folding and stability, leading to altered biological functions, as seen in sickle-cell anemia.
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Sickle-Cell Anemia Pathophysiology
Sickle-cell anemia is a genetic disorder caused by a mutation in the hemoglobin gene, leading to the production of abnormal hemoglobin (HbS). This altered hemoglobin causes red blood cells to deform into a sickle shape under low oxygen conditions, resulting in blockages in blood vessels, pain, and reduced oxygen delivery. The drastic change in function stems from the altered properties of the hemoglobin molecule due to the amino acid substitution.
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Related Practice
Textbook Question
What is the anticodon on tRNA for each of the following codons in an mRNA?
c. GAA
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Provide a reason why there is no vaccine for the common cold.
Textbook Question
A base substitution changes a codon for an enzyme from GCC to GCA. Why is there no change in the amino acid order in the protein?
Textbook Question
How is CRISPR different from earlier recombinant DNA techniques?
Textbook Question
A base substitution for an enzyme replaces leucine (a nonpolar amino acid) with alanine. Why does this change in amino acids have little effect on the biological activity of the enzyme?