2008年12月英语六级考试阅读理解模拟试题

　　Vitamins K

　　Vitamin K, phylloquinone, is found in dark green leafy vegetables such as spinach and kale. It is a fat soluble vitamin which is involved in the clotting process of blood. In the intestines bacteria synthesize a number of important clotting factors which need vitamin K. Without vitamin K cuts can fail to heal and internal bleeding can occur.

　　Vitamins C

　　Vitamin C is a water soluble vitamin, known chemically as ascorbic acid. It is found in citrus fruits such as oranges and lemons, and also in potatoes and tomatoes. The main function of vitamin C is the formation of connective tissues such as collagen. It is also known to be an antioxidant which helps to remove toxins and aids the immune system. A lack of vitamin C leads to Scurvy, a condition experienced by sailors on long journeys when they did not have fruit in their diets. Scurvy causes painful, bleeding gums. As vitamin C is water soluble, it is not toxic in high doses as it can be excreted in the urine, very high doses can however cause diarrhea.

　　Vitamins B

　　B group vitamins have a wide range of roles acting as co-enzymes in metabolic pathways. They are found in most plant and animal tissues involved in metabolism, therefore foods such as liver, yeast and dairy products are all rich in B group vitamins. Deficiency of B group vitamins include dermatitis, fatigue and malformation of red blood cells.

　　1. An adult needs about 12,000kJ of energy a day from ________.

　　A. the cell

　　B. the respiring process of carbohydrates

　　C. fats in the cell

　　D. a balanced diet

　　2. Carbohydrates are ultimately absorbed into cells in the process of _______.

　　A. digestion

　　B. respiration

　　C. oxidization

　　D. mobilization

　　3. The Essential Amino Acids which build part of proteins can be obtained from______.

　　A. stomach

　　B. body tissues

　　C. the body

　　D. the diet

　　4. The ultimate cause of kwashiorkor is lack of ________.

　　A. protein

　　B. carbohydrates

　　C. vitamins

　　D. diet

　　5. Vitamins are called “micronutrients” in that _________.

　　A. excessive fat soluble vitamins can be excreted in the urine

　　B. the body only requires small amount of vitamins

　　C. a dose of 3300mg of vitamins can be considered toxic

　　D. the high concentrations of water soluble vitamins are toxic

　　6. Night blindness is a disease normally caused by lack of __________.

　　A. fat soluble vitamins

　　B. water soluble vitamins

　　C. vitamin A

　　D. innate disability