Tuesday, June 16, 2015

原子电中性,分子电中性: rsi twisting in the air 病毒(Virus)由一种核酸分子(DNA或RNA)与蛋白质(Protein)构成或仅由蛋白质构成(如朊病毒)。病毒个体微小,结构简单。病毒没有细胞结构,由于没有实现新陈代谢所必需的基本系统,所以病毒自身不能复制。但是当它接触到宿主细胞时,便脱去蛋白质外套,它的核酸(基因)侵入宿主细胞内,借助后者的复制系统(酶系统和能量),按照病毒基因的指令复制新的病毒,按照病毒基因的指令复制新的病毒。

病毒(Virus)由一种核酸分子(DNA或RNA)与蛋白质(Protein)构成或仅由蛋白质构成(如朊病毒)。病毒个体微小,结构简单。病毒没有细胞结构,由于没有实现新陈代谢所必需的基本系统,所以病毒自身不能复制。但是当它接触到宿主细胞时,便脱去蛋白质外套,它的核酸(基因)侵入宿主细胞内,借助后者的复制系统,按照病毒基因的指令复制新的病毒。


病毒是敌,还是友

    文/闻玉梅      来源:科学画报

    与动植物的细胞相比,病毒是非常小的微生物,大小以纳米为单位计算,一般要在电子显微镜下才可以看到它们的真容。病毒没有细胞结构,没有新陈代谢所必需的基本系统,一般只由一种类型的核酸(DNA或RNA)与蛋白质构成,或仅由蛋白质构成(如朊病毒),致使自身不能复制。因此病毒必须在活的细胞里生长与复制。当病毒接触到宿主细胞时,经细胞表面受体侵入宿主细胞,通过脱去蛋白质“外套”,其核酸(基因)借助细胞的酶系统和能量,按照病毒基因的指令复制新的病毒。所以,有科学家甚至认为,病毒本身并不是活的生物体,因为离开活的细胞,病毒就不能繁殖,它看上去更像是由蛋白质包裹的一组基因。
    可就是这样一个肉眼看不见的“小不点”,却可以轻而易举地使人患病。有数据表明,全球有3/4的传染病是由病毒引起的,其中在我国狂犬病的死亡率最高,达到100%;而发病率最高的则是各种病毒性肝炎,肝炎病毒会造成人体肝脏不同程度的损伤,甚至发展为肝硬化和肝癌。病毒的危害远不止于此。2003年,SARS流行,尽管我国当时只有5000多人被感染,但疫情却使我国的产品难以出口,许多国家不敢与中国进行贸易,造成了很大的经济损失。再如,我们比较熟悉的禽流感,它可以“秒杀”几百万只鸡,这对养殖业来说就是灾难。事实上,禽流感很难控制,极容易传播,因为禽流感病毒非常“善变”。科学家发现,禽流感的病毒基因可分为8段,而且容易与其他病毒基因进行交换。如H7N9病毒就是由禽流感病毒的部分基因和人流感病毒的部分基因杂交而来,所以这些病毒可以轻松地在动物和人之间传播。
    病毒微小,种类繁多,“狡猾”又“善变”,及时掌握病毒的“敌情”,将有助于科学防治很多疾病。不仅如此,随着生物科技的发展,科学家正积极利用病毒的一些特性,通过改造病毒,将它们“化敌为友”,让病毒能“友好”地为人类服务。例如,很多用于预防传染病的疫苗就是利用病毒制成的。
    如題 學過理化的大大都知道分子一定是電中性 
小弟有一個問題
CO2是電中性  因為C是-4價  O是-2價  所以成電中性

那位什麼CO CO3也是電中性呢??

  • 2011-06-08 16:48:01 補充那生物圈大大 你的意思是說 CO和CO3的碳原子是碳的同位素的意思囉?

最佳解答

  • 發問者自選
回答者: ( 初學者 3 級 )
回答時間:2011-06-15 14:54:35
[ 檢舉 ]
你對電價數  缺乏基本概念

用CO2來說

   o = c = o   

   因為氧(O)  的陰電性 3.0 高於 碳  2.5
   因此當任何其中一邊  C=O  共用電子成為共價鍵 的時候

   電子實際上不是平均的分享 
   電子會偏向 O  稍微遠離 C
   所以會形氧帶有負電的傾向 -2

   碳被電子遠離  因此會有帶偏正電   +4



   回到問題
   電價決定的時候要堅守規則
   氧優先於碳
  90% 以上氧都是 -2

   因此答案如下
             CO   CO2      CO3
C    +2      +4    +6
O      -2    -2       -2

總電價   0     0       0
 

"只要是分子   也就是不是離子   一定就是電中性"




   不是電中性的只有離子
   高中教材來說    通常只能容在水中  或是其他液體

   例如    NO3-  

N    +5

O    -2

總電價   (+5 )*1  +  (-2)*3   = -1



PS:
   這題跟同位素完全無關


In biology, one of the factors that defines a living thing from an inanimate object is the organism's ability to carry out chemical reactions that are crucial for its survival. Even one-celled organisms are capable of hundreds of chemical reactions within their cell walls. Imagine the infinite amount of reactions that a large organism such as a human carries out. None of these reactions are possible without enzymes.
Enzymes are biological catalysts or assistants. Enzymes consist of various types of proteins that work to drive the chemical reaction required for a specific action or nutrient. Enzymes can either launch a reaction or speed it up. The chemicals that are transformed with the help of enzymes are called substrates. In the absence of enzymes, these chemicals are called reactants.
To illustrate the speed and efficiency of enzymes, substrates can be transformed to usable products at the rate of ten times per second. Considering that there are an estimated 75,000 different enzymes in the human body, these chemical reactions are performed at an amazing rate. On the other hand, in the absence of enzymes, reactants may take hundreds of years to convert into a usable product, if they are able to do so at all. This is why enzymes are crucial in the sustenance of life on earth.
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Generally, enzymes work on substrates in one of three ways: substrate orientation, physical stress, and changes in substrate reactivity. Substrate orientation occurs when an enzyme causes substrate molecules to align with each other and form a bond. When an enzyme uses physical stress on a substrate, it in effect grips the substrate and forces the molecule to break apart. An enzyme that causes changes in substrate reactivity alters the placement of the molecule’s electrons, which influences the molecule’s ability to bond with other molecules.
Enzymes have active sites where they come into contact with particular substrates. The catalytic properties of enzymes are a cyclic process. Once a substrate has come into contact with the active site of an enzyme, it is modified by the enzyme to form the end product. Once the process is complete, the enzyme releases the product and is ready to begin the process with new substrates. Enzymes are never wasted and always recycled.
The absence of enzymes is responsible for many diseases. In humans, a tragic disease called phenylketonuria (PKU), which causes severe mental retardation and even death in infants, is the result of the absence of one type of enzyme. Tay-Sachs disease is a similarly tragic result of an enzyme deficiency. It causes retardation, paralysis, and often death in early childhood when left untreated.
Our ability to alter enzymes by inhibiting their functioning abilities has resulted in hundreds of life saving drugs. One example is penicillin, a well-known antibiotic that can cure syphilis, pneumonia, and other illnesses. Penicillin works by bonding to the active sites of the disease-causing bacteria’s enzymes, ultimately destroying the bacteria’s ability to survive and reproduce.

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