Actually I believe the relevant part of the Constitution you're speaking of is the Bills of Revenue which is Article 1, Section 7, Clause 1 of the United States Constitution which states
The relevant text
This is how the SCOTUS justified the individual mandate. A Bill of Revenue is also known as a tax. I'd be surprised if the appellate court can shoot this one down, although I'm curious how an appellate court can overturn a SCOTUS decision. Can you explain that process to me? Last I knew the SCOTUS was the highest court and no lower court can overturn a higher court's decision.
SCOTUS is supposed to rule on the portions of a law based on the arguments brought before it. Since the fact that the ACA originated in the Senate was not part of the arguments, and it was ruled Constitutional based on the power of Congress to tax, it may be objected to on that basis. If you look at all the different ways plaintiffs have gone about trying to get abortion overturned or our Second Amendment rights restricted, you will see that one Supreme Court decision need not affect all of a law, just a part of it, as the recent SCOTUS decision which overturned parts of the Voting Rights law, I believe.