Insulin is such a vital secretion of the pancreas in the human body that without it, our body would not function normally. It is responsible for breaking down the food we eat and converting it to energy and then storing that energy. Lack of insulin means that the pancreas are not producing insulin which leads to diabetes. That means that there is a concentration of glucose in the blood rather than being distributed to cells to carry out functions. This can lead to kidney failures, nerve damaging stomach problems and problems in the eyes.
For each of the examples, simple diffusion, carrier, and channel mediated, each type involves the flow down a concentration gradient. This means that the molecules flow from an area of high concentration to an area of low concentration. In turn, this allows for a passive process, meaning no ATP is needed! I hope this explains your question.
