El Helalyaالمؤسسة
تاريخ التسجيل : 08/08/2008
 |  موضوع: الجذور الحرة ^^^تسبب السرطان ^^^والعديد من الأمراض ^^ فما هي الجذور الحرة السبت 5 يونيو 2010 - 19:22 | |
| بسم الله الرحمن الرحيم
Free Radicals
الجذور
الحرة
فكرة من 100 عام
It is now 100 years since Moses Gomberg
discovered the
first organic free radical
ويقصد بهذا المصطلح ذرة
فاقدة الكترون ( محتاجه الكترون)
، ولهذا فهي ذرة غير مستقرة
وتتوق للاستقرار بالحصول
على هذا الالكترون .
كيف نفسر هذا الكلام
هناك أربع
طرق لحدوث الجذور الحرة
1/Initiation
Some
molecules contain relatively weak covalent bonds, which under
the
correct energetic conditions, can break to give two molecules or
atoms,
each containing an unpaired electron. This type of bond breaking
is
known as homolysis or homolytic bond cleavage.
(visible-light, UV or X-rays)
Propagation /2
Once the radical has been formed it can undergo
abstraction (e.g. cyclisation
) or addition (e.g. polymers
) reactions, to form more stable radical or non-radical products. These
propagation reactions generally work because they break weak bonds in
the
reactants and make strong bonds in the products.
Termination /3
In
competition with propagation reactions are termination reactions.
Whereas
propagation reactions have one radical reactant and one radical
product,
termination reactions lead to the destruction of radicals (i.e.
no
new radicals are produced from these reactions). An important
termination
reaction involves the combination (or coupling) of radicals
to form
dimers.
Chain reactions /4
Most
radical reactions involve a chain mechansim in which an initial
radical
undergoes a series of propagation reactions. These reactions
ultimately
lead to regeneration of the initial radical and the formation
of a
chain.
Chlorination of methane
تسميات اخرى
In
biochemistry,
the free radicals of interest are often referred to as reactive
oxygen species
(ROS) because the
most
biologically significant free radicals are oxygen-centered
المضار
المصاحبة للجذور الحرة
Free radical damage
within cells has been linked to a range of
disorders including cancerarthritisatherosclerosisAlzheimer's
diseasediabetes
This involvement is
not at all surprising as free radical chemistry
is an important aspect
of phagocytosis,
inflammation,
and apoptosis. Cell
suicide, or
apoptosis, is the body's way of controlling cell death
and involves free
radicals and redox signalling. Redox factors play
an even greater part
in other forms of cell death such as necrosis or autoschizis
الأسباب
environmental pollutioncigarette smoke ultraviolet
lightdrugschemicals...
طرق الوقاية
Antioxidants
مضادات الاكسدة
Antioxidants are molecules that scavenge for
harmful oxygen-centred radicals (HO., RO
They react with
the
harmful radicals before they get a chance to damage the bodyNaturally occurring antioxidants include vitamins C and
E, which are found in many plants
(including citrus fruits and
vegetables),
nuts and seeds.
Indeed, vitamin E is
often
present in margarine and this prevents radical reactions leading
to
deterioration (or rancidity).
Antioxidants
have been proposed to play an
important role in preventing cancer,
heart disease, immune-deficiency
diseases and ageing. However, the jury is
still out as to which groups,
if any, benefit from taking antioxidant
supplements
  
  
كاتبة دكتور محمود ابو البكاش
 الموضوع : الجذور الحرة ^^^تسبب السرطان ^^^والعديد من الأمراض ^^ فما هي الجذور الحرة المصدر :منتديات تقى الإسلامية الكاتب: El Helalya |
|
El Helalyaالمؤسسة
تاريخ التسجيل : 08/08/2008
| | موضوع: رد: الجذور الحرة ^^^تسبب السرطان ^^^والعديد من الأمراض ^^ فما هي الجذور الحرة السبت 5 يونيو 2010 - 19:23 | |
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الجنه تنادينيالاشراف العام
تاريخ التسجيل : 16/05/2010
| |
واسلاماهالمراقبة العامة
تاريخ التسجيل : 23/06/2009
| | موضوع: رد: الجذور الحرة ^^^تسبب السرطان ^^^والعديد من الأمراض ^^ فما هي الجذور الحرة الجمعة 8 يوليو 2011 - 20:08 | |
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