Combine flour, baking powder, sugar, baking soda and salt in large bowl. Cut in shortening with a pastry blender or 2 knives until mixture resembles fine crumbs.

Make a well in the center of dry mixture; add the buttermilk all at once. Stir buttermilk into flour mixture until mixture forms soft dough that leaves sides of bowl.

Preheat oven to 450°.

Turn out dough onto well-floured surface. Knead dough 10 times; roll into 8 inch square. Cut dough into sixteen 2 inch squares. Place the dough squares 1 1/2 inches apart on large ungreased baking sheets.

Bake until biscuits are light golden, about 10 to 12 minutes. Remove biscuits from baking sheets and serve warm.