Soften the yeast in warm water. In a large mixing bowl, measure out andstir together the flour, sugar, baking powder, salt, and baking soda. Cut in the shortening until the mixture resembles fine crumbs. Stir in the yeast mixture and the buttermilk until just combined and dough leaves side of the bowl.
Sprinkle flour on your work surface, turn dough out onto flour. Kneed about 20 strokes until dough holds together, sprinkling with flour if dough is too sticky. Pat or roll out to ½ inch thickness. Using a 2 inch biscuit cutter, cut out biscuits, placing an inch apart on an ungreased baking sheet. Reroll remaining scraps and cut out rest of biscuits.
Cover baking sheets with a clean kitchen towel. Let rise 1 to 1 ½ hours or until double in size. Preheat oven to 400 degrees. Bake biscuits 12-14 minutes or until bottoms of biscuits are a golden brown. Remove immediately from baking sheets.
You can place the dough in a lightly greased mixing bowl, cover with plastic wrap and refrigerate up to 3 days.