ACS EXAM 2025-2026 UPDATE WITH COMPLETE
SOLUTIONS. ALREADY GRADED
In a helix, the R groups on the amino acid residues: - Correct Answer ->> The R groups of the
amino acids stick outward from the α helix
pI - Correct Answer ->> pH value where the net charge of an ionizable species is zero
Peptide Bonds (resonance) - Correct Answer ->> polarity of the peptide bond increases; has
partial double bond character; carbonyl carbon and amide N are coplanar- free rotation about
the bond is restricted
Ramachandran plot - Correct Answer ->> displays allowed regions of protein folding space. Phi-
psi angle combinations are shown. Green areas indicate which combinations are most favorable
role of b-marcaptoethanol in reducing disulfide bonds - Correct Answer ->> used to fully break
the covalent disulfide bond. Used in Anfinsen's experiment
nucleotides - Correct Answer ->> monomer unit for nucleic acids and are composed of
nitrogenous base, 5-carbon sugar, and a phosphate group
DNA - Correct Answer ->> more stable; carrier of genetic information, double stranded
RNA - Correct Answer ->> less stable; intermediate expression of genetic information. Can form
secondary structure by H-bonding with itself.
tRNA - Correct Answer ->> transfer RNA, holds amino acids used in protein synthesis, wobble
position
rRNA - Correct Answer ->> ribosomal RNA, part of the ribosome
siRNA - Correct Answer ->> small interfering RNA; short term silencing of coding genes; targets
mRNA for degradation
miRNA - Correct Answer ->> microRNA, silencing and post-transcriptional regulation of gene
expression
Purines - Correct Answer ->> 2 rings, adenine and guanine
Pyrimidines - Correct Answer ->> one ring, cytosine, thymine, and uracil (in RNA only)
A-T/U - Correct Answer ->> has 2 H bonds
SOLUTIONS. ALREADY GRADED
In a helix, the R groups on the amino acid residues: - Correct Answer ->> The R groups of the
amino acids stick outward from the α helix
pI - Correct Answer ->> pH value where the net charge of an ionizable species is zero
Peptide Bonds (resonance) - Correct Answer ->> polarity of the peptide bond increases; has
partial double bond character; carbonyl carbon and amide N are coplanar- free rotation about
the bond is restricted
Ramachandran plot - Correct Answer ->> displays allowed regions of protein folding space. Phi-
psi angle combinations are shown. Green areas indicate which combinations are most favorable
role of b-marcaptoethanol in reducing disulfide bonds - Correct Answer ->> used to fully break
the covalent disulfide bond. Used in Anfinsen's experiment
nucleotides - Correct Answer ->> monomer unit for nucleic acids and are composed of
nitrogenous base, 5-carbon sugar, and a phosphate group
DNA - Correct Answer ->> more stable; carrier of genetic information, double stranded
RNA - Correct Answer ->> less stable; intermediate expression of genetic information. Can form
secondary structure by H-bonding with itself.
tRNA - Correct Answer ->> transfer RNA, holds amino acids used in protein synthesis, wobble
position
rRNA - Correct Answer ->> ribosomal RNA, part of the ribosome
siRNA - Correct Answer ->> small interfering RNA; short term silencing of coding genes; targets
mRNA for degradation
miRNA - Correct Answer ->> microRNA, silencing and post-transcriptional regulation of gene
expression
Purines - Correct Answer ->> 2 rings, adenine and guanine
Pyrimidines - Correct Answer ->> one ring, cytosine, thymine, and uracil (in RNA only)
A-T/U - Correct Answer ->> has 2 H bonds
