An accessory organ that produces enzymes that aids in the digestion of all macronutrients

Pancreas

Explanation:

Pancreas is the organ which is involved in digestion of all the macro nutrients inside the body. This organ produces various types of digestive juices that helps in the digestion of proteins, carbohydrates, et cetera.

The pancreas secretes hormones responsible for the digestion of the carbohydrates.

The enzymes such as trypsin, carboxypeptidase and chymotrypsin helps in the digestion of protein and carbohydrates.

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.