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
2025-02-09
9
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 phrase this aspect of vision refers to
选项
A、The adeptness to see clearly without depending on proteins.
B、The aptitude to rapidly adjust to the changes in the amount of light.
C、The ability to see clearly in complete darkness.
D、The competence to rapidly adjust from natural light to artificial light.
答案
B
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3949043.html
相关试题推荐
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
ImportanceofVitaminsVitamins,whichcomeinman
Thefat-solublevitaminsarestoredinbodyfatandmaythereforeaccumulatein
Theimportanceofagriculturecannotbeoverstated.Morethan50percentof
Theimportanceofagriculturecannotbeoverstated.Morethan50percentof
随机试题
奉上鲜花一统,聊表心意,敬请翁教授和夫人笑纳。我俩都在想念你。当你读着这张慰问卡时,希望它能让你知道—我们正在思念你,我们还想用一种特别亲切的方式告诉你
政府增加购买性支出,对社会的生产和就业以及国民收入分配的影响是()。A.对两
非随机性时间数列包括()。 Ⅰ.非平稳性时间数列 Ⅱ.季节性时间数列
()交易,即除套期保值类以外的衍生产品交易。A.保值类衍生产品 B.非套期保
下列哪项不是何首乌的功能A.润肠B.截疟C.解毒D.止血E.补肝肾
各种运输方式内外部的各个方面的构成和联系,就是( )。 A.运输系统
“能感受到家乡的发展变化并为此感到高兴”该社会领域目标的典型表现所属的年龄段是(
女性,40岁,A型预激综合征患者,突然出现心慌、心悸来诊。心电图示心率180次/
下列哪项有助于Crohn病的诊断A.环形溃疡 B.反复发作的肛周脓肿 C.全
甲患有癌症,通过互联网从乙处购买A药自用,后经药品监督管理部门查实,A药为乙从国
最新回复
(
0
)