if we take food rich in lime juice,then

1. action of ptyalin on starch is enhanced
2. action of ptyalin on starch is reduced
3. action of ptyalin on starch is unaffected
4. action of ptyalin on starch stops

Dear Student,
Please find below the solution to your problem.

Normal pH in healthy mouth is about 6.5-7, so slightly acidic to neutral. Lime juice contains a mild organic acid (citric acid), so consuming food with lime juice will cause a lowering of pH in your mouth. As a consequence, the activity of ptyalin (salivary α-amylase, an enzyme which breaks starch down into maltose and dextrin, making digestion to glucose easier - and your body really needs glucose as a source of energy!) will be inhibited if pH drops below the optimum range of 5.6-6.9. In extremis, if enough acidic food is consumed together with food containing starch, probably the effect would be a slower digestion of starch since ptyalin is not much helping anymore (by starting breaking the starch from the mouth).

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