How are simple sugars used for energy compared to more complex sugars

The complex sugars like starch and glycogen are converted into simple sugar by action of enzymes like amylase, maltase.  

Amylase present in the saliva starts digesting the complex starch in the mouth then the food goes into the stomach where food is mixed with HCl and then it moves to the duodenum which contains more digestive enzymes.

Amylase converts complex carbohydrates into disaccharides and disaccharides is converted into monosaccharide by enzymes like maltase, sucrase, lactase.

Then simple monosaccharides like glucose is absorbed in the body and moves to a different cell. The energy is released by the oxidation of these monosaccharides like glucose which is used by the cells to perform metabolic activities.

Complex carbohydrates can not be used directly so they are converted into simpler form to provide energy to the body.

unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.