Whilst inorganic molecules, such as the mineral calcium, are broken down into smaller molecules, they aren't broken down into simpler structures, because they are already in their simplest form.
Large organic molecules such as starch need to be broken down into simpler forms - maltose and glucose respectively via digestion. Other organic larger molecules are broken down into simpler forms like protein to amino acids and lipids to fatty acids and glycerol etc.
Glucose is one of several simple sugars (monosaccharides).
Biological catalysts are what help to break down these large molecules (polymers) to simpler ones (monomers), they are called enzymes.