Name: how catalysts lower reaction barriers
Uploaded: 2019-03-11T09:21:09.000Z
Duration: 1 min 26 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Matter And Its Interactions

HS-PS1-4

Activation Energy

طاقة التنشيط هي الطاقة اللازمة لبدء تفاعل كيميائي بين المتفاعلات الموجودة غالبًا ما يُزود المصدر بالطاقة الحرارية مما يدفع بالجزيئات لتتحرك بصورة أسرع وتتصادم مع بعضها بعضاًمسبببة بكسر روابط المتفاعلات وبالتالي تتطلب المتفاعلات الأصلية طاقة حرة ليحدث التفاعل ممثلاًبصفة الجزء الشاق من هذا المنحنى هذا هو مقدار طاقة التنشيط للتفاعل في الذروة،والمعروفة باسم حالة الانتقال تكون الجزيئات غير المقيدة بحالة غير مستقرة بينما ترتبط الذرات من جديد بقيود جديدة يطلقون طاقة مجانية في البيئة الأمر الذي يظهر كجزء التدهور للتفاعل في الوقت الذي يستقلب البشر السكر والدهون للحصول على الطاقة إذا اُستخدمت الطاقة الحرارية لكسر هذه الجزيئات ستُطلق الكثير من الطاقة المجانية على شكل حرارة فتُفسد البروتينات في الخلية بدلاًمن ذلك،المواد المعروفة باسم المحفزات تضاف خصيصا لتنظيم معدل الأيض،كتسريعها مثلاًيقلل محفز بيولوجي،وهو إنزيم من طاقة التنشيط اللازمة لكسر القيود ويتيح لردود الفعل الحدوث بمعدلات معقولة دون أضرار خلوية

روبنسون ، بيتر ك. "الإنزيمات: المبادئ وتطبيقات التكنولوجيا الحيوية". مقالات في الكيمياء الحيوية 59 (15 نوفمبر 2015): 1-41. [<a href = "https://doi.org/10.1042/bse0590001" target = "__blank" >المصدر</a>]

طاقة التفعيل

طاقة التنشيط هي الحد الأدنى من الطاقة اللازمة للتفاعل الكيميائي للمضي قدماً. كلما زادت طاقة التنشيط ، كان معدل التفاعل أبطأ. ومع ذلك ، فإن إضافة الحرارة إلى التفاعل سيزيد من المعدل ، لأنه يتسبب في تحرك الجزيئات بشكل أسرع ويزيد من احتمال تصادم الجزيئات. يمثل تصادم الروابط وانكسارها المرحلة الشاقة من التفاعل ويولد حالة الانتقال. حالة الانتقال هي حالة غير مستقرة عالية الطاقة من المتفاعلات. يشكل تكوين روابط كيميائية ومنتجات نهائية جديدة ، وإطلاق الطاقة الحرة مرحلة انحدار من التفاعل. تزيد المحفزات من معدل التفاعل عن طريق خفض طاقة التنشيط. على سبيل المثال ، في علم الأحياء ، تزيد الإنزيمات التي تستقلب السكر والدهون من معدل حدوث تحللها وفي نفس الوقت تمنع الإنتاج الزائد للطاقة الحرة التي من شأنها أن تفسد البروتينات في الخلية.

<h4>المحفزات</h4>

المحفز هو مادة تزيد من معدل التفاعل عن طريق خفض طاقة التنشيط ، وفي هذه العملية ، تجدد نفسها. يوفر المحفز مساراً أو آلية بديلة لحدوث التفاعل ويسرع كلا من التفاعلات الأمامية والعكسية. في علم الأحياء ، تعتبر الإنزيمات أمثلة على المحفزات لأنها تقلل من طاقة التنشيط المطلوبة للتفاعلات في التمثيل الغذائي الخلوي.

على سبيل المثال ، يقوم الإنسان باستقلاب السكر والدهون للحصول على الطاقة. تعتبر الإنزيمات مهمة للإنسان لتحطيم هذه الجزيئات ، لأنه إذا تم استخدام الطاقة الحرارية وحدها ، فإن الطاقة الحرة المنبعثة في شكل حرارة من شأنها أن تتسبب في إفساد البروتينات في الخلية. علاوة على ذلك ، فإن الطاقة الحرارية لا تحفز على وجه التحديد جميع التفاعلات. ومع ذلك ، فإن الإنزيمات ترتبط فقط بمفاعلات كيميائية معينة ، تسمى الركائز ، وتقلل من طاقة التنشيط لتحفيز التفاعلات الخلوية الانتقائية.

طاقة التنشيط هي الحد الأدنى من الطاقة اللازمة للتفاعل الكيميائي للمضي قدما. كلما زادت طاقة التنشيط ، كان معدل التنشيط أبطأ ...

Education

JoVE Core

Biology

علم الأحياء

Cellular Processes

العمليات الخلوية

Metabolism

عملية التمثيل الغذائي (الأيض)

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

how catalysts lower reaction barriers

Activation energy is the minimum energy a chemical reaction needs to keep going. When the activation energy is higher, the reaction usually happens more slowly. Adding heat can speed the reaction because molecules move faster and collide more often.

As reactants collide, bonds break and the reaction moves through an uphill phase. That step creates the transition state, which is an unstable, high-energy state of the reactants. After that, new bonds form, products appear, and free energy is released in the downhill phase.

Catalysts speed up reactions by lowering the activation energy. A catalyst is a substance that takes part in the reaction pathway and then regenerates itself. It offers an alternate mechanism and speeds up both the forward and reverse reactions.

In biology, enzymes are catalysts that help cells control metabolism. They help break down sugar and fat for energy, and they do it without releasing too much free energy as heat. That matters because excess heat could denature proteins in the cell.

Enzymes are also selective. They bind only to specific reactants called substrates and lower the activation energy for those reactions. Thermal energy alone would not be as selective and could drive many reactions at once, but enzymes support specific cellular reactions instead.

How Catalysts Lower Reaction Barriers

what is metabolism?

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activation energy

Activation energy is the minimum energy a chemical reaction needs to keep going. When the activation energy is higher, the reaction usually happens more slowly. Adding heat can speed the reaction because molecules move faster and collide more often. As reactants collide, bonds break and the reaction moves through an uphill phase. That step creates the transition state, which is an unstable, high-energy state of the reactants. After that, new bonds form, products appear, and free energy is...

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enzyme inhibition

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feedback inhibition

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cofactors and coenzymes

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key terms and concepts

Learn how heat, transition states, catalysts, and enzymes affect reaction speed. See how lowering activation energy helps cells break down sugar and fat.

How Catalysts Lower Reaction Barriers | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

biology

Tennessee Academic Standards

Energy

CHEM1.PS3.3

Minnesota Academic Standards in Science

9-12

3.1.1 9C.2.2.1.1

Alabama Course of Study Science

Physical Science

9-12.PS.1.1

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How Catalysts Lower Reaction Barriers

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