The food demand at the bottom of the "balanced diet pagoda" is the most, and the food demand at the top is the least. The first layer from bottom to top is cereal, which mainly provides sugar. The second layer is vegetables and fruits, which mainly provide vitamin C; The third layer is fish, meat and eggs, the fourth layer is soybean milk, and the third and fourth layers mainly provide protein and calcium; The fifth layer is grease, which mainly provides fat. The basic principles of dietary guidelines for China residents are as follows: food is diverse, mainly cereals, and the thickness is matched; Eat more vegetables, fruits and potatoes; Eat milk, soybeans or their products every day; Eat proper amount of fish, poultry, eggs and lean meat; Reduce the consumption of edible oil, and the diet is light and salt-free.
(1) As can be seen from the Y curve in Figure B, fat is digested in D's small intestine, first emulsified into fat particles by bile in the small intestine, and then completely digested into glycerol and fatty acids by lipase in intestinal juice and pancreatic juice.
(2) As can be seen from the curve X, the digestion of starch starts from the mouth of A, and starch is decomposed into maltose under the action of salivary amylase, and then it reaches the small intestine, and then it is completely decomposed into glucose by the small intestinal juice and pancreatic juice in the small intestine. Therefore, curve X represents the digestion process of sugar (starch).
(3) protein is an important raw material for building and repairing the body. The growth and development of human body and the repair and renewal of damaged cells are inseparable from protein. In addition, protein can be decomposed to provide energy for human life activities. Because children and teenagers are developing rapidly, they need a lot of protein.
(4) The main ingredient of sweets or snacks is sugar, which is the main source of human energy. If you seldom exercise on weekdays, it will lead to overnutrition. These substances will be converted into fat and stored under the skin, causing obesity and making you gain weight quickly. If you eat little food every day, you will only eat snacks and some fruits, which will lead to malnutrition and affect the normal growth and development of your body. You should have three meals a day, eat on time and take a balanced intake.
So, the answer is: (1) y; (2) oral cavity (or a); (3) protein; (4) no; Balance nutrition and strengthen exercise.