Biochemistry
Biochemistry
9th Edition
ISBN: 9781305961135
Author: Mary K. Campbell, Shawn O. Farrell, Owen M. McDougal
Publisher: Cengage Learning
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Chapter 3, Problem 1RE

RECALL How do D-amino acids differ from L-amino acids? What biological roles are played by peptides that contain D-amino acids?

Expert Solution & Answer
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Interpretation Introduction

Interpretation:

The difference between d-amino acid and l-amino acid, and the biological role played by peptides that contain d-amino acids is to be explained.

Concept information:

Amino acids are the building blocks of proteins.

These are more than 900 amino acids, but among them only 20 amino acids are found in proteins.

The structure of amino acids contains a carboxyl group and an amino group, both bonded to the α carbon. The α-carbon is also bonded to a hydrogen atom and a R (side chain) group. The general structure of amino acids is as follows:

Biochemistry, Chapter 3, Problem 1RE , additional homework tip  1

Answer to Problem 1RE

The stereochemistry of d-amino acids and l-amino acids are different around the α-carbon of the amino acid structure, and the peptide that contains d-amino acids protects us from bacterial infection.

Explanation of Solution

All amino acids except glycine have two forms. These two forms of the same amino acid are referred to as stereoisomers. Amino acids having an active chiral carbon (carbon bonded with four different groups) show stereoisomerism. These stereoisomers are referred to as d-amino and l-amino acids.

d-amino acids have the amino acid group on the right side of the α-carbon, whereas l-amino acids have the amino acid group on the left side of the α carbon.

The l-form and d-form of amino acid are as follows:

Biochemistry, Chapter 3, Problem 1RE , additional homework tip  2 Biochemistry, Chapter 3, Problem 1RE , additional homework tip  3

l-Amino acid is the most common form of amino acid which occur in proteins. d-Amino acids are not common in proteins, but are found in bacterial cell wall, and also used as antibiotics which indicates that it plays a role in the protection from bacterial infections.

Conclusion

The difference between l- and d- amino acids is due to the position of the amino acid group around the α carbon of the amino acid. Moreover, d-amino acids are used against bacterial infections by incorporating them in antibiotics.

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Chapter 3 Solutions

Biochemistry

Ch. 3 - MATHEMATICAL Sketch a titration curve for the...Ch. 3 - MATHEMATICAL Sketch a titration curve for the...Ch. 3 - MATHEMATICAL An organic chemist is generally happy...Ch. 3 - MATHEMATICAL Sketch a titration curve for aspartic...Ch. 3 - REFECT AND APPLY Suggest a reason why amino acids...Ch. 3 - REFECT AND APPLY Write equations to show the ionic...Ch. 3 - REFECT AND APPLY Based on the information in Table...Ch. 3 - REFECT AND APPLY If you were to have a mythical...Ch. 3 - REFECT AND APPLY What would be the pI for the...Ch. 3 - REFECT AND APPLY Identify the charged groups in...Ch. 3 - REFECT AND APPLY Consider the following peptides:...Ch. 3 - REFECT AND APPLY In each of the following two...Ch. 3 - REFECT AND APPLY Could the amino acid glycine...Ch. 3 - RECALL Sketch resonance structures for the peptide...Ch. 3 - RECALL How do the resonance structures of the...Ch. 3 - REFECT AND APPLY Would the peptide group be planar...Ch. 3 - Prob. 27RECh. 3 - REFECT AND APPLY Consider the peptides...Ch. 3 - REFECT AND APPLY Would you expect the titration...Ch. 3 - REFECT AND APPLY What are the sequences of all the...Ch. 3 - REFECT AND APPLY Answer Question 30 using...Ch. 3 - REFECT AND APPLY Most proteins contain more than...Ch. 3 - REFECT AND APPLY If the amino acids alanine and...Ch. 3 - Prob. 34RECh. 3 - REFECT AND APPLY Would the presence of a chiral...Ch. 3 - REFECT AND APPLY What might you infer (or know)...Ch. 3 - Prob. 37RECh. 3 - REFECT AND APPLY Suggest a reason why the amino...Ch. 3 - REFECT AND APPLY Consider the peptides...Ch. 3 - Prob. 40RECh. 3 - Prob. 41RECh. 3 - REFECT AND APPLY You are studying with a friend...Ch. 3 - Prob. 43RECh. 3 - REFECT AND APPLY Suggest a reason (or reasons) why...Ch. 3 - Prob. 45RECh. 3 - REFECT AND APPLY Speculate on the properties of...Ch. 3 - RECALL What are the structural differences between...Ch. 3 - RECALL How do the peptide hormones oxytocin and...Ch. 3 - RECALL What is the role of the disulfide bond in...Ch. 3 - RECALL Is it possible to form cyclic peptides...Ch. 3 - Prob. 51RECh. 3 - RECALL What types of experiments led to evidence...Ch. 3 - Prob. 53RECh. 3 - THOUGHT QUESTION Imagine we identify a gene that...
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