Unformatted text preview: energy in a closed system is constant -— it can neither be created nor destroyed but simply changes form. When products come
out of the reaction with less energy the extra energy is released in another form. The released energy might be heat or a form
of energy that can be used to perform work. In energy requiring reactions energy is added and the products possess more energy than the reactants. only-unth- W..- Mimi's-i G0 to the next screen: When reactant molecules enter into a reaction, their
"- OM”""'°’“"M'"' conversion into product molecules does not occur abruptly The reacting molecules
9:: 9?:53m33: u" go into a high-energy intermediate form called a transition state. In the graphic you
0"” ommnm'ﬂ-d-“mmw' will see alugp 1n the middle ofthe curve, known as an Wt,
C" and IS due to the fact that the tential ener of the tran
f ... n th f ei tants of the products
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ET:- ° W... a Go to the next screen: Let’s take the example of burning paper.
Paper does not spontaneously combust. Go to the next screen: Energy, such as a ﬂame or heat provided
through a magnifying glass gets the ﬁre started by overcoming the activation ener anier. When this paper is burning it is in the
transt on state. G0 to the next screen: For reactants to become products or vice
versa, molecules must have sufﬁcient potmtial energy to surmount the
activation energy barrier, and they must acquire some extra energy called
activation energy. G0 to the next screen: In this situation the molecules have
overcome the activation energy barrier and entered into the transition
state. If molecules must acquire extra energy to surmount the activation
energy barrier and react, where does this extra energy come from?
Molecules acquire this energy by colliding with each other, which
happens all the time because they are in constant thermal motion The signiﬁmee of the activation energy barrier 15 that it limits how fast; maction can go. Most collisions do not generate sufﬁcient energy to surmount the activation energy barrier.
They simply emerge om e collision In an unaltered state. - CCUV’ Och 4'\ W 9.4 6‘ e451 .‘YVDLQJ—MQS W‘u )us+ bowwz . I , I“ ed and»
w: m “mm G0 to the next screen: The Mof a metabolic reaction is a measure 0‘1"va
*- of how fast it consumes reactants and generates products. Metabolic
reactions are accelerated or catalyzed by special molecules called Quad-v engymes. Enzymes act as catalysts to increase the magtion rate.
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- Spring '07