Question

describe how food other than glucose can enter the respiratory metabolic pathway

Answer 1

Well, when you're talking about metabolic respiration, you're talking about basically, the krebs cycle. Do you understand that?

Answer 2

Do you also understand that glucose is a carbohydrate, which stores energy. I believe the question they are asking is what other sources can be produced if glucose is not sufficently present.

Answer 3

There are lots of types of food that can be fed into the Kreb's cycle, some of them just enter the cycle at different points. Any of them would need to be in monomer form first, that is as a single simple sugar or fatty acid etc.