LEHNINGER PRINCIPLES OF BIOCHEMISTRY
2026 MOCK PAPER COMPREHENSIVE REVIEW
NOTES ANALYTICAL SUMMARY
◉ residue.
Answer: A single unit in a polymer; for example, an amino acid in a
polypeptide chain. The term reflects the fact that sugars,
nucleotides, and amino acids lose a few atoms (generally the
elements of water) when incorporated in their respective polymers.
◉ R group.
Answer: (1) Formally, an abbreviation denoting any alkyl group. (2)
Occasionally, used in a more general sense to denote virtually any
organic substituent (e.g., the R groups of amino acids).
◉ chiral center.
Answer: An atom with substituents arranged so that the molecule is
not superposable on its mirror image.
◉ enantiomers.
Answer: Stereoisomers that are nonsuperposable mirror images of
each other.
, ◉ absolute configuration.
Answer: The configuration of four different substituent groups
around an asymmetric carbon atom, in relation to ᴅ- and ʟ-
glyceraldehyde.
◉ ᴅ, ʟ system.
Answer: Make sure that the molecule is drawn as the Fischer
projection in which the carboxylic acid group is on top and the side
chain on bottom. If the amine group is on the right of the carbon
chain, assign the label ᴅ to the compound; if it is on the left of the
carbon chain, assign the label ʟ.
◉ polarity.
Answer: (1) In chemistry, the nonuniform distribution of electrons
in a molecule; polar molecules are usually soluble in water. (2) In
molecular biology, the distinction between the 5' and 3' ends of
nucleic acids.
◉ absorbance, A.
Answer: A measure of the capacity of a substance to absorb light of a
specified wavelength. It is equal to the logarithm of the reciprocal of
the transmittance.
◉ zwitterion.
2026 MOCK PAPER COMPREHENSIVE REVIEW
NOTES ANALYTICAL SUMMARY
◉ residue.
Answer: A single unit in a polymer; for example, an amino acid in a
polypeptide chain. The term reflects the fact that sugars,
nucleotides, and amino acids lose a few atoms (generally the
elements of water) when incorporated in their respective polymers.
◉ R group.
Answer: (1) Formally, an abbreviation denoting any alkyl group. (2)
Occasionally, used in a more general sense to denote virtually any
organic substituent (e.g., the R groups of amino acids).
◉ chiral center.
Answer: An atom with substituents arranged so that the molecule is
not superposable on its mirror image.
◉ enantiomers.
Answer: Stereoisomers that are nonsuperposable mirror images of
each other.
, ◉ absolute configuration.
Answer: The configuration of four different substituent groups
around an asymmetric carbon atom, in relation to ᴅ- and ʟ-
glyceraldehyde.
◉ ᴅ, ʟ system.
Answer: Make sure that the molecule is drawn as the Fischer
projection in which the carboxylic acid group is on top and the side
chain on bottom. If the amine group is on the right of the carbon
chain, assign the label ᴅ to the compound; if it is on the left of the
carbon chain, assign the label ʟ.
◉ polarity.
Answer: (1) In chemistry, the nonuniform distribution of electrons
in a molecule; polar molecules are usually soluble in water. (2) In
molecular biology, the distinction between the 5' and 3' ends of
nucleic acids.
◉ absorbance, A.
Answer: A measure of the capacity of a substance to absorb light of a
specified wavelength. It is equal to the logarithm of the reciprocal of
the transmittance.
◉ zwitterion.
