2016年英语四级考试模考强化实战训练题二

　　Part Ⅰ Writing (30 minutes)

　　Directions: For this part, you are allowed 30 minutes to write a short essay entitled The cet4v.com Getting Certificates cet4v.com should write at least 150 words following the outline given below.

　　1.大学校园内各种证书的报考十分火热

　　2.大学生考证的利弊

　　3.考证面前，我的选择

　　The cet4v.com Getting Certificates on Campus

　　【参考答案】

　　Part ⅠWriting

　　【范文与点评】

　　The cet4v.com Getting Certificates on Campus

　　①Currently, getting certificates is quite popular on campus. The advertisements for training schools occupy a large proportion of the bulletin board, and booksellers fill their shelves with many reference books. And eager students spare their money and time for these courses and books.

　　②There are several advantages in this matter. The biggest one is that with more certificates, students are accessible to more and better job opportunities. Besides, they can make more contacts with the outside world in the course of getting certificates.③However, every coin has two sides. The pursuit of certificates is no exception. Some students believe that ④the more certificates, the better.⑤One can hardly make progress this way, but can become bookish easily. Some of them even neglect their routine learning in the process of getting certificates.

　　From my viewpoint, certificates certify students’ previous efforts. ⑥But whether these pieces of paper can benefit students or not, depends on what they have really gained. Therefore, before dazzling choices, we must have a clear attitude and scientific strategy, and then certificates are beneficial.

　　①开门见山，说明这种现象的存在，接下来，作者从学校海报栏的广告，书店经营者和学生三方面来进一步说明该现象。

　　②首先论述其优点，并用了一些连接词表明句与句之间的关系。该部分的结构是There are several advantages...The biggest one ...Besides,...。

　　③接下来论述的是其存在的缺点，并用However表示转折。

　　④The +形容词比较级，the +形容词比较级，表示“越…，越…”。学会使用这种结构能让文章增色不少。

　　⑤这个句子用了hardly和easily，形成鲜明的对比，给人印象深刻。

　　⑥本句结构whether...or not 引出本文观点。Part Ⅱ Reading Comprehension (Skimming and Scanning) (15 minutes)

　　Main Energies for the Body

　　A balanced diet is one that provides an adequate intake of energy and nutrients for maintenance of the body and therefore good health. A diet can easily be adequate for normal bodily functioning, yet may not be a balanced diet.

　　Carbohydrates

　　Carbohydrates are a rapid source of energy, they are the body's fuel. The bulk of a balanced diet should be made from carbohydrates. If eaten in an excess of the dietary requirements carbohydrates are easily stored as fats in the cells, although carbohydrate is the first source of energy in the body. An average adult requires about 12,000kJ of energy a day, most of this is supplied by the respiration of carbohydrates in the cells.

　　Carbohydrates are used principally as a respiratory substrates, i.e. to be oxidized to release energy for active transport, macromolecule synthesis, cell division and muscle contraction. Carbohydrates are digested in the duodenum and ileum and absorbed as glucose into cells. Sources of carbohydrates such as starch are rice, potatoes, wheat and other cereals. Sugars are also carbohydrates, sources of sugars are refined sugar - sucrose, which is a food sweetener and preservative and fruit sugars - fructose. If the diet lacks carbohydrate stores of fat are mobilized and used as an energy source.

　　Proteins

　　Protein is not a direct source of energy in the body, it is used primarily for growth and repair of body tissues while remaining an energy source as a last resort. Proteins fulfill a wide variety of roles in the body. They are broken down in the stomach and intestines to amino acids which are then absorbed. The body can only form 8 amino acids to build proteins from, the diet must provide Essential Amino Acids (EAAs) which are synthesized into proteins which can be structural, i.e. collagen in bone, keratin in hair, myosin and actin in muscle; metabolic enzymes, hemoglobin, protective antibodies and communicative hormones.

　　Sources of protein include meat, fish, eggs and pulses. The diet needs to provide 8 EAAs as the body is unable to synthesis proteins without these molecules. 2 other amino acids are synthesized from EAAs so if the diet lacks the original EAAs these other two will not be present either. Phenylalanine is converted to tyrosine and methionine is converted to cysteine. Cells draw upon a pool of amino acids for protein synthesis which either come from dietary protein digested and absorbed in the gut and the breakdown of body protein such as muscle. However, unlike fats and carbohydrates there is no store of amino acids for cells to draw on, any amino acid in excess of immediate bodily requirements is broken down into urea and excreted. It is therefore important to maintain the dietary intake of protein everyday. If the body lacks protein, muscle wasting occurs as muscle is broken down.

　　If protein is lacked in a diet a person develops kwashiorkor which is caused when high levels of carbohydrates are eaten to overcome the lack of protein in the diet. One symptom of kwashiorkor is the abnormal collection of fluid around the abdomen due to the lack of protein in the blood. The body cannot retain water by osmosis and fluid accumulates in tissues causing them to become waterlogged.

　　Vitamin Categories

　　Vitamins cannot be synthesized by the body so must be supplied by diet. Vitamins have no common structure or function but are essential in small amounts for the body to be able to utilize other dietary components efficiently.

　　Vitamins fall into two categories, fat soluble vitamins such as vitamin A, D, E and K which are ingested with fatty foods and water soluble vitamins such as the B group vitamins and vitamin C. Vitamins are known as micronutrients because only small quantities are required for a healthy diet, in fact fat soluble vitamins can be toxic in high concentrations, for example the body stores vitamin A, or retinol, in the liver as it is toxic if kept in high concentrations in the blood stream, a dose of more than 3300mg of vitamin A can be considered toxic. Water soluble vitamins such as vitamin C and B groups vitamins can be excreted in the urine if in excess in the diet.

　　Vitamins A

　　Vitamin A is essential to the proper functioning of the retina in the eye and the epithelial tissues. A lack of vitamin A results in dry, rough skin, inflammation of the eyes, a drying or scarring of the cornea - xerophthalmia, which occurs when the secretion of lubricating tears is stopped, the eyelids become swollen and sticky with pus. Mucous surfaces of the eye may become eroded allowing infection to set in, leading to ulceration and destruction of the cornea. Night blindness - an inability to see in dim light can also occur. Rod cells in the retina of the eye detect light of low intensity, they convert vitamin A into a pigment, rhodopsin, which is bleached when light enters the eye. Rod cells resynthesis rhodopsin, but if there is a deficiency of the vitamin, rod cells can no longer function and the result is night blindness. Epithelial cells use retinol to make retinoic acid, an intracellular messenger used in cell differentiation and growth. Without retinoic acid epithelial cells are not maintained properly and the body becomes susceptible to infections, particularly measles and infections of the respiratory system and gut.

　　Xenophthalmia is common among children who's diets consist of mainly cereals with little meat or fresh vegetables, this is common in Indonesia, Bangladesh, India and the Philippines.

　　Vitamins D

　　Vitamin D, or calciferol, is another fat soluble steroid vitamin which functions to stimulate calcium uptake from the gut and its deposition in bone. vitamin D acts as a hormone when converted by enzymes in the gut and liver into an active form of "active vitamin D", which stimulates epithelial cells in the intestine to absorb calcium. vitamin D is therefore essential in growing children's diets to enable the growth of strong bones. Without adequate amounts of vitamin D children can develop rickets, which is the deformation of the legs caused when they lack calcium to strengthen the bones. In adults a lack of vitamin D in the diet can lead to osteomalacia, a progressive softening of the bones which can make them highly susceptible to fracture.

　　Vitamin D is made by the body when exposed to sunlight and is stored in the muscles, however, if the skin is rarely exposed to the sunlight or is dark little vitamin D is produced. Foods such as eggs and oily fish are all rich in vitamin D.

　　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

　　7. The main function of vitamin D is to prevent adults from ________.

　　A. the growth of strong bones B. fracture

　　C. a progressive softening of the bones D. calcium uptake from the gut

　　8. Although the human body produces vitamin D normally, it fails to do so if there is not enough ______________.

　　9.

　　vitamin C is seen as an antioxidant is that it drives __________ out of the body.

　　10. If you are in lack of B group vitamins, you should turn to _______________.