Keith is a college student. He is extremely busy studying and working part-time. Keith sleeps in late and therefore does not take time for breakfast. He rushes off to class. At lunch he has time for only French fries. When he gets home from school, he eats canned corn (only corn, nothing else) and washes it down with water. Then, he goes to work, only to start the same routine the next day.

When Keith is confronted about his poor diet, he responds, "The French fries are a good source of carbohydrates. Since they are fried in oil, I get my daily requirement of fat. At supper time, I eat corn and it has a lot of amino acids in it." You, a medical student, suggest that Keith see a doctor. Keith complies and makes an appointment with a doctor. The doctor's report looks like this: Keith is pale and underweight, his urine and blood pH are low, and the ketones in the urine and blood are high. The Na+ concentration in the blood is low. Keith seems to have possible nerve problems. The doctor explains that Keith is pale due to anemic conditions brought on by the poor diet. With a poor protein diet, Keith's erythrocytes may not be making adequate hemoglobin. Because his diet is very low in carbohydrates, his body is metabolizing fat, which is causing the weight loss. By products of fat metabolism are ketones, which are acidic. This accounts for the increase in ketones in the urine and the blood and a drop in the pH. A drop in blood pH will inhibit the small intestine from putting Na+ into the bloodstream. Sodium ions are necessary for proper nerve function. In short, Keith needs to begin eating well-balanced meals.

a. Why is corn considered to be an incomplete protein?

b. How are ketones formed?

c. How are sodium ions involved in the nervous system?

d. How does this scenario relate to fad diets?