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Activation energy



The amount of energy (in joules) needed to convert all the molecules in one mole of a reacting substance from a ground state to the transition state intermediate


The activation energy is a term coined by the Swedish scientist, Svante Arrhenius in 1889. It means the amount of energy expressed in joules that is required to convert the molecules in one mole of a reactant from a ground state to the transition state. It can also mean the energy that an atomic system must have before an emission or chemical reaction can occur. The activation energy of a reaction may be denoted by Ea.

In relation to biology (such as biochemistry), the activation energy (or energy of activation) pertains to the energy needed to initiate a reaction. For instance, the activation energy required to breakdown glucose into pyruvic acid in respiration is two ATP.

Accordingly, enzymes speed up chemical reactions by reducing the activation energy of a reaction. Moreover, this reduction by an enzyme allows biological reactions to proceed rapidly at relatively low temperatures tolerable by living organisms.1

Also called:

See also:

1P. J. Russell. (2008). "Biology: The Dynamic Science, Volume 1." Canada (Belmont): Cengage Learning. ISBN 9781111795559.

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Re: Increase in free energy in glycolysis

Increase in free energy just refers to Gibbs free energy. That free energy comes from enthalpy (internal ... glucose-6-phosphate and PFK1 making Fructose-1,6-Bisphosphate is made to overcome the activation energy of the subsequent step. I don't know what you understanding of biochemistry ...

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by daniel.kurz
Wed Feb 05, 2014 3:03 am
Forum: Molecular Biology
Topic: Increase in free energy in glycolysis
Replies: 3
Views: 4060

Re: Enzymes and activation energy.

QUESTION: Explain how enzymes lower activation energy

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by misunderstandingbio
Sun Sep 15, 2013 3:37 pm
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Topic: Enzymes and activation energy.
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Cellular Respiration

1) the problem is the energy, which you need/get from respective steps. Also, as you may know, you need first to iniciate the breakdown by activation of glucose by phosphorylation. So, which step of Glc degradation would you like to connect ...

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by JackBean
Fri Dec 31, 2010 10:53 am
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Topic: Cellular Respiration
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Questions to elementary biochemistry

... and clear. 1. Enzymes doesn't influence equibrilium, but they lower the activation energy. I wonder how this is possible? Isn't the activation energy expressed in free Gibbs ...

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by strikken
Mon Dec 27, 2010 12:39 pm
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Topic: Questions to elementary biochemistry
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by kolean
Mon Nov 30, 2009 2:28 pm
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Topic: Alleles
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