Multiple Choice
In human nutrition, approximately how much metabolizable energy does 1 gram of dietary protein provide?
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1. Introduction to Biochemistry
Proteins
Multiple Choice
In standard protein biosynthesis, how many different genetically encoded amino acids are commonly incorporated into proteins?
A
64
B
20
C
16
D
22
Verified step by step guidance1
Understand that the genetic code consists of codons, which are sequences of three nucleotides in mRNA that specify amino acids during protein synthesis.
Recognize that there are 64 possible codons (4 nucleotides ^ 3 positions = 64), but not all codons correspond to different amino acids; some are stop signals.
Recall that in standard protein biosynthesis, the genetic code encodes 20 common amino acids that are incorporated into proteins.
Note that although there are 22 genetically encoded amino acids in some organisms (including selenocysteine and pyrrolysine), the standard set commonly referred to in most organisms is 20.
Therefore, the answer to how many different genetically encoded amino acids are commonly incorporated into proteins is 20.
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