Combine dry yeast and warm water in a small bowl; let stand for 5 minutes to activate.

In a large bowl, combine the buttermilk and the yeast mixture.

In a separate large bowl, whisk together flour, baking powder, baking soda, salt, and sugar.

Cut in the shortening or margarine into the dry ingredients until the mixture resembles coarse crumbs.

Add the buttermilk mixture to the dry ingredients and mix until just combined. Do not overmix.

Turn the dough out onto a lightly floured surface and gently pat it into a 1-inch thick rectangle.

Cut out biscuits using a biscuit cutter or a knife.

Place the biscuits on a baking sheet.

Let the biscuits rest for 10 minutes.

Bake in a preheated oven at 400°F (200°C) for 15-20 minutes, or until golden brown.