Answer to Question 1
Vitamin C acts like a battery re-charger to re-charge copper or iron atoms (by reducing them) so that they may act as batteries and provide the charge needed for enzymes to catalyze another reaction.
Answer to Question 2
Pernicious anemia is an autoimmune disease in which antibodies destroy the stomach cells that produce intrinsic factor. Pernicious anemia will still be present with adequate consumption of vitamin B12 in the diet. Afflicted individuals need vitamin B12 injections because they can't absorb vitamin B12 via the GI tract without intrinsic factor.