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
6
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] According to the paragraph 6, which of the following is true of carotene?
选项
A、They can be found in green vegetables.
B、They are found in all animal livers and dairy products.
C、They convert into vitamin A once consumed.
D、They are chemical substances human body needs in order to survive.
答案
C
解析
转载请注明原文地址:https://www.tihaiku.com/zcyy/3334491.html
相关试题推荐
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br]【26】[
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br]【25】[
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br]Thetu
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br][orig
Atthestartofthetutorial,thetutoremphasisestheimportanceof[br][orig
Atthestartofthetutorial,thetutoremphasisestheimportanceof[originalte
VitaminsAandCand(mostof)theBvitamins(areretain)(infoods)thathave
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
随机试题
TheEnglish(36)______settlementsinNorthAmericabeganinthe17thcentur
______(sell)thehouse,Mikehadalargesumofmoneyathisdisposal.Havingso
12ThingsI’veLearnedFromTravelingAroundtheWorldforThreeYears
关于尿胆原代谢的错误叙述是A.结合胆红素排入肠道后被转化为尿胆原 B.大部分尿
预防维生素A缺乏措施中错误的是()A.饮食中多供给含维生素A及胡萝卜素的食物
急性阑尾炎穿孔局限性腹膜炎的手术治疗要点中下列哪项错误A.注意保护切口,防止感染
竖向设计地面按其整平连接形式可分为()。A.平坡式 B.台阶式 C.集
关于我国宪法修改,下列哪一选项是正确的?A、我国修宪实践中既有对宪法的部分修改,
甲公司股票的当前市价为10元,有一种以该股票为标的资产的看跌期权,执行价格为8元
女,66岁。反复双膝关节疼痛12年,逐渐加重3年,活动时关节有弹响。体检:双膝关
最新回复
(
0
)