Textbook Question
What is the sequence of atoms along the "backbone" of a protein?
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 62
The endorphins are a group of naturally occurring neurotransmitters that act in a manner similar to morphine to control pain. Research has shown that the biologically active parts of the endorphin molecules are simple pentapeptides called enkephalins. Draw the structure of the methionine enkephalin with the sequence Tyr-Gly-Gly-Phe-Met. Identify the N-terminal and C-terminal amino acids.
Verified step by step guidance1
Step 1: Understand the structure of a peptide. A peptide is a chain of amino acids linked by peptide bonds. Each amino acid has an amino group (-NH₂), a carboxyl group (-COOH), and a unique side chain (R group). The peptide bond forms between the carboxyl group of one amino acid and the amino group of the next.
Step 2: Write the sequence of the peptide. The given sequence is Tyr-Gly-Gly-Phe-Met. This means the peptide starts with Tyrosine (Tyr) and ends with Methionine (Met). Each amino acid is connected by peptide bonds in the order provided.
Step 3: Identify the N-terminal and C-terminal amino acids. The N-terminal amino acid is the one with the free amino group (-NH₂) at the start of the sequence, which is Tyrosine (Tyr). The C-terminal amino acid is the one with the free carboxyl group (-COOH) at the end of the sequence, which is Methionine (Met).
Step 4: Draw the structure of the peptide. Start with the N-terminal Tyrosine (Tyr), followed by Glycine (Gly), another Glycine (Gly), Phenylalanine (Phe), and finally Methionine (Met). Ensure that each amino acid is connected by a peptide bond (-CO-NH-). Include the side chains for each amino acid: Tyr has a phenol group, Gly has a hydrogen atom, Phe has a benzyl group, and Met has a thioether group.
Step 5: Verify the structure. Check that the peptide chain is correctly drawn with the proper sequence, peptide bonds, and side chains. Confirm that the N-terminal (Tyr) has a free amino group and the C-terminal (Met) has a free carboxyl group.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Endorphins and Enkephalins
Endorphins are neurotransmitters produced by the body that help relieve pain and induce feelings of pleasure. Enkephalins are a specific type of endorphin, consisting of short chains of amino acids known as peptides. They bind to opioid receptors in the brain, mimicking the effects of morphine and playing a crucial role in pain modulation.
Amino Acid Structure
Amino acids are the building blocks of proteins, each consisting of a central carbon atom, an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group). The sequence of amino acids in a peptide determines its structure and function. In the context of enkephalins, the specific sequence of amino acids influences their ability to bind to receptors and exert biological effects.
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N-terminal and C-terminal
In a peptide or protein, the N-terminal refers to the end of the molecule that has a free amino group (-NH2), while the C-terminal is the end with a free carboxyl group (-COOH). Identifying these terminals is essential for understanding the directionality of the peptide chain, which is crucial for its synthesis and function. In methionine enkephalin, the N-terminal is Tyrosine (Tyr) and the C-terminal is Methionine (Met).
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Related Practice
Textbook Question
How could you make the zwitterion of aspartic acid more soluble in water?
Textbook Question
Identify the amino acids present in the peptide shown and name the peptide using the three-letter abbreviations.
Textbook Question
Use the three-letter abbreviations to name all tripeptides that contain valine, methionine, and leucine.
Textbook Question
Identify the N-terminal and C-terminal amino acids of the peptide.
Textbook Question
Write structural formulas for the two dipeptides that contain leucine and aspartate.