首页
登录
职称英语
Importance of Vitamins Vitamins, which come in man
Importance of Vitamins Vitamins, which come in man
游客
2024-01-05
46
管理
问题
Importance of Vitamins
Vitamins, which come in many different types all of which are quite diverse in chemical configuration and function, can be any of several organic substances that are separated into water-soluble and fat-soluble groups. Originally defined as organic compounds obtainable in a normal diet and capable of maintaining life and promoting growth, vitamins are differrent from carbohydrates, fats, and proteins in function, as well as in the quantities in which organisms require them. So critical are vitamins to a body’s essential strength and health that if they are absent from the diet or not properly absorbed by an organism, a specific deficiency disease may develop.
The term vitamin originated from "vitamine," a word first used in the early 19th century to designate a group of compounds considered vital for life (though the term "accessory food factor" sometimes is used interchangeably to refer to these substances). Like other nutrients, vitamin consumption is imperative to keep our bodies functioning properly, and if there is a lack of vitamin consumption, the body will fail to react in a way that’s considered healthy. Lack of vitamin A will result in various disorders that most commonly involve the eye and the tissues around it. One of the earliest symptoms of vitamin A deficiency is nyctalopia, the medical term for night blindness, which causes a visual failure to adapt quickly from light to darkness and an inability to see in the dark. This aspect of vision is normally dependent on rhodopsin, a protein found in the eye that maintains itself only in the presence of vitamin A; in the lack of vitamin A, rhodopsin will malfunction.
These earlier symptoms are quite harmless but the side effects can become increasingly serious if not treated early on. If the deficiency is severe and persists, especially in malnourished infants and children, a condition known as xerophthalmia--when the eyes are sensitive to light, the secretion of lubricating tears is stopped, and the eyelids become swollen and develop pus -- may develop. Furthermore, the mucous surfaces of the eye may become eroded, allowing infection to set in, thus leading to ulceration and other destructive changes of the cornea and other structures of the eye, resulting eventually in blindness.
A Early signs of vitamin A deficiency may also be reflected in changes in the membranes of the mouth, throat, and respiratory and genito-urinary passages where the lining membranes become malnourished and dry and lose their cilia, the tiny hairlike projections that normally help in clearing away foreign particles. B The natural immune system is weakened and if insufficient intake of vitamin A is prolonged, the skin may become dry and rough. C Vitamin A deficiency may also result in defective bone and teeth formation and in poor general growth.D
However, an excessive intake of vitamin A can also cause severe damages to the body causing a symptom called "hypervitaminosis A", which happens when a person takes in more than 150 milligrams of vitamin A over a long period of time; the vitamins are stored in the liver and can reach dangerous level because the A vitamins are not employed to make the bodies stronger, but rather, stored as toxic material. Excessive amounts of vitamin A can cause nausea, dryness of skin, blurred vision, drowsiness, and bone pain.
Vitamin A can be found in all animal livers, in milk products, and in many yellow and green leafy vegetables which contain carotenes, chemically related substances that are converted to vitamin A in the body. There are various other vitamins that the human body needs in order to survive; the excessive intake of vitamin A, or the lack of intake of other vitamins, causes detriment to the human body--at all times, moderation is key. [br] The word malnourished in the passage is closest in meaning to
选项
A、emaciated.
B、melancholy.
C、ill.
D、hungry.
答案
A
解析
转载请注明原文地址:http://tihaiku.com/zcyy/3334486.html
相关试题推荐
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br][orig
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br]【25】[
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br]Anexa
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br][orig
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br][orig
Atthestartofthetutorial,thetutoremphasisestheimportanceof[originalte
(Whencannedusing)propermethods,foodsuffers(no)lossillvitaminsor(ano
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
随机试题
Jackarrivedattherailwaystationat4o’clockintheafternoon.Itwas4o’cl
Punctuality(准时)meansobservingregularorappointedtime.Amanwhogetsu
图示三种金属材料拉伸时的曲线,下列中的哪一组判断三曲线的特性是正确的?A.a
显微镜凝集试验常用于A.奋森疏螺旋体 B.雅司螺旋体 C.梅毒螺旋体 D.
从异体移植术后发生免疫排斥时间来分类,以下属于急性排斥反应的是A.移植术后2小时
区域似大地水准面精化时,下列数据中,不需要的是()。A:区域沉降测量数据B:区
行政法律关系具体包括行政主体与行政相对人的直接管理关系、宏观调控关系、服务关系、
关于《绿色建造技术导则》资源节约中,减少固体废弃物产生的规定与要求,表述正确的为
某火力发电企业安全管理人员每天进行一次现场巡回检查,其行走路线依次为:控制室-省
下列按水平投影面积1/2计算建筑面积的有()。A.屋顶上的水箱 B.有顶
最新回复
(
0
)