1. You know, I'm a member of the cooking club.
(What is the role of 'You know' in this sentence?)
2. You know that I'm a member of the cooking club.
(Are #2 the same as #1? What is the difference between them in meaning?)
http://owl.english.purdue.edu/owl/resource/607/02/
The comma you used correctly in #1 is because of rule #2c here. The words "You know" are just introductory; they indicate that the speaker assumes that the listener already knows the facts in the main clause of the sentence.
Sentence 2 is stating what the speaker knows the listener knows; the only real difference is in pronunciation -- no pause after "know" as in #1.
1. In the sentence, "You know, I'm a member of the cooking club," the phrase "You know" is used as a filler or discourse marker. It is an informal way to initiate or continue a conversation by assuming or reminding the listener that they already have some prior knowledge or awareness of what is being talked about. It functions to establish a level of familiarity or shared understanding between the speaker and the listener.
2. Both sentences, "You know, I'm a member of the cooking club" and "You know that I'm a member of the cooking club," have similar meanings. However, the second sentence, "#2," is more explicit in its presentation of the information. By using the conjunction "that," it indicates that the speaker assumes the listener is already aware of the fact mentioned (being a member of the cooking club) and introduces it directly into the sentence. The first sentence, "#1," is more conversational and assumes the listener's prior knowledge without explicitly stating it.