Molecules are considered stereoisomers when:
A. they rotate plane-polarized light to the left only.
B. they have the same chemical and structural formulas but the structures are not superimposable.
C. they have three different groups bound to a central carbon.
D. they have structures differing only by one group.
E. they contain no chiral centers.
Molecules that contain an asymmetric carbon are said to be:
A. chiral.
B. optically inactive.
C. achiral.
D. enantiomeric.
E. hydrophobic.
Why are weak chemical interactions so important in biological systems?
What will be an ideal response?
Which of the following does not describe an instance in which weak chemical bonds are useful in biological systems?
A. the bonding of antibodies to the antigens they recognize
B. the folding of proteins into their active conformation
C. the stabilization of DNA double-stranded helices
D. the stabilization of protein structure by the creation of salt bridges between oppositely charged amino acids
E. a gecko's ability to climb surfaces such as glass
Which of the following atoms cannot participate in biological hydrogen bonds?
A. nitrogen
B. oxygen
C. carbon
D. both nitrogen and oxygen
E. both oxygen and carbon
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