Multiple Choice
Which of the following statements about surface tension is true?
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13. Liquids, Solids & Intermolecular Forces
Intermolecular Forces
Multiple Choice
In DNA, what type of intermolecular force primarily holds complementary base pairs (A–T and G–C) together across the two strands?
A
Ionic bonds between positively and negatively charged bases
B
London dispersion forces between the phosphate groups of the backbone
C
Covalent bonds between the nitrogenous bases on opposite strands
D
Hydrogen bonding between polar functional groups on the bases
Verified step by step guidance1
Identify the nature of the interaction between complementary base pairs in DNA, which involves adenine (A) pairing with thymine (T) and guanine (G) pairing with cytosine (C).
Recall that the bases are connected across the two strands by non-covalent interactions rather than covalent bonds, allowing the strands to separate during processes like replication.
Understand that ionic bonds are unlikely because the bases themselves are not charged species; the charged parts of DNA are mainly in the phosphate backbone.
Recognize that London dispersion forces are weak and generally occur between nonpolar molecules or parts, and the phosphate groups are part of the backbone, not the base pairing interface.
Conclude that the primary intermolecular force holding complementary bases together is hydrogen bonding, which occurs between specific polar functional groups on the bases (e.g., between NH and carbonyl groups), providing specificity and stability to the DNA double helix.
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