This type of membrane protein enables cells to catalyze specific chemical reactions at the inner or outer surface of their plasma membrane

Enzymes are proteins which enable cells to catalyze specific chemical reactions at the inner and outer surface of the plasma membrane. Enzymes are found in all the cells of the body including plasma membrane cells. Enzymes function by speeding up chemical reactions in the body; they do this by lowering the activation energy which the reaction requires to occur.

The answer is d. when it begins to fall back to the child's hand