Iodine solution is added to a cake solution. The color changes to purple. Based on this result, what biological molecules are present in the cake solution?

starch, because it's reacts with iodine forming a purple solution and it is present in cake

Starch

Explanation:

The cake solution contains starch. Starch is a mixture of amylose and amylopectin. Amylose results in purple-deep blue color when it comes in contact with iodine. In absence of starch, this tri iodide anion solution has brown color. When starch is added, they both form a charge transfer complex by slipping of iodine molecule inside amylose coil which results in purple-blue black color. Iodine reagent is made by dissolving iodine in aqueous solution of potassium iodide. Color intensity decreases with increasing temperature, low pH and in presence of organic solvents.