The reason why the quotation marks are needed in the second sentence is not that the nouns are abstract, but that they are nouns. The general rule is that when one wishes to refer to a word, rather than to what the word normally signifies, one uses the word in quotation marks, or, alternatively, in italics. (The rule is, however, not followed very stringently in everyday communications.)
Incidentally, the first sentence seems to be rather odd. If it supposed to be about the words or concepts 'do', 'love', etc., then it should begin with something like 'The words for human . . . '. On the other hand, if it really is about the actions themselves, then it would be more natural to say ' . . . actions like doing, loving . . . '.
Finally, if one normally uses double quotation marks, one should use single ones in the text that is already enclosed in a pair of double ones. (If one normally uses single ones, then one should use double ones in the text that is already enclosed in single ones.)