Multiple Choice
Given the amino acid glutamic acid (which has a negatively charged side chain at physiological pH), with which of the following amino acids would it be more likely to form an ionic interaction?
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3. Amino Acids
Amino Acid Groups
Multiple Choice
How many standard amino acids are commonly found in proteins of living organisms?
A
12
B
22
C
20
D
16
Verified step by step guidance1
Step 1: Understand the context of the question. Proteins in living organisms are composed of amino acids, which are organic molecules that serve as the building blocks of proteins.
Step 2: Recall that there are 20 standard amino acids commonly found in proteins. These amino acids are encoded by the genetic code and are universally used in protein synthesis across living organisms.
Step 3: Note that these 20 amino acids include examples such as glycine, alanine, valine, leucine, and others. They are classified based on their side chains into categories like polar, nonpolar, acidic, and basic.
Step 4: Recognize that while there are other amino acids (e.g., selenocysteine and pyrrolysine), these are considered non-standard and are not universally found in all proteins.
Step 5: Conclude that the correct answer to the question is 20, as this is the number of standard amino acids commonly found in proteins of living organisms.
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