Concept explainers
What two
a. an R-group and a hydroxyl group
b. an N–H group and a carbonyl group
c. an amino group and a hydroxyl group
d. an amino group and a carboxyl group
Introduction:
The amino acid is the basic structural unit of the proteins. There are total 20 amino acids found in the living system. At isoelectric point (pH or potential of hydrogen), an amino acid does not have any net charge. The basic structure of amino acids is shown below:
Answer to Problem 1TYK
Correct answer:
An amino group and a carboxyl group
Explanation of Solution
Explanation/Justification for the correct answer:
Option (d) is given as a carboxyl group along with an amino group. Functional groups of amino acids are responsible for bonding between two amino acids. The polypeptide chain consists of several amino acids. When a peptide bond is formed, a hydroxyl (–OH) group is lost from the carboxyl group of an amino acid and an H (hydrogen atom) from the amino group of another amino acid is also lost. This dehydration (loss of one H2O molecule) reaction results in a peptide bond. Hence, option (d) is correct.
Explanation for incorrect answers:
Option (a) is given as an R- group and a hydroxyl group. R group or side chain decides the identity of an amino acid, for example, glycine, which is the simplest amino acid, has a hydrogen atom as its R group. So, it is a wrong answer.
Option (b) is given as an N-H group and a carbonyl group. Any functional group, which has an O (oxygen) atom attached to the C (carbon) atom through double bond (-C=O) is called carbonyl group. COOH (carboxylic acid) is also a type of the carbonyl group. So, it is a wrong answer.
Option (c) is given as an amino group and a hydroxyl group. The carboxylic acid of the amino acid contains one hydroxyl group, which gets lost when the amino acid undergoes peptide bond formation with an amino group of another amino acid. So, it is a wrong answer.
Hence, options (a), (b), and (c) are incorrect.
The amino group and a carboxyl group are functional groups bounded to the central carbon of every free amino acid monomer.
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Chapter 3 Solutions
Biological Science (6th Edition)
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