Question

why ptyalin breaks down only raw starch into maltose"

Answer 1

The net result of this process is conversion of a 3-phosphoglycerate molecule into a molecule of the three-carbon sugar glyceraldehyde 3-phosphate (G3P). In three turns of the cycle, six molecules of G3P are produced, six ATP are converted to ADP and Pi, and six NADPH are converted to NADP+ and H+.