HELP WITH COURSEWORK . . .NOW (on enzymes and activation energy)

[Cloud]

I need some help with the theory section of my biology coursework on catalase (an enzyme).

 

I need to make a QUANTATATIVE PREDICITON.

 

THIS IS WHAT I HAVE SO FAR:

 

So far I have wrote about the 10 degree rule

Quantitative prediction

 

I predict, in quantitative terms, that at every ten degrees Celsius increment the reaction rate will double.

 

This is based on the activation energy needed to start a reaction. The activation energy is the amount of energy needed in a collision for hydrogen peroxide and catalase molecules to start a successful reaction. If this energy is not reached by the molecules, a reaction will not take place. In most cases, the majority of molecules will not attain the activation energy needed as shown in this example graph which plots a line of a certain temperature against the number of molecules(y axis) and energy (x-axis).

 

GRAPH

 

 

Blue area = molecules which haven’t attained enough energy to activate

Grey area = molecules which have attained activation and are reactable

 

The graph shows that most of the molecules haven’t attained the activation energy required. The grey region shows the number of molecules that have reached the activation energy which is significantly less than the blue area. The activation energy is a certain amount and therefore has been plotted to show the barrier between successful reactions and unsuccessful molecules.

 

 

So if, for example, the temperature was raised by 1 degree Celsius each molecule will have proportionally 1 more joule of kinetic energy (if 1 degree = 1 joule). Therefore each particle will have greater energy so more will pass the activation energy point:

 

 

graph

 

 

From the above graph, it is clear that more molecules have successfully reacted. The 10 degree rule for chemical reactions states:

 

“for every ten degrees celsius the reaction rate doubles”

 

 

This is understandable because if I was to present another graph showing what would be ten times that of the above graph (therefore being a 10 degrees celsius increment upon the first graph) it would show that the amount of molecules that have successfully reached the activation energy has doubled – since the amount of molecules have doubled so has the rate:

 

GRAPH

 

This should also apply to biochemical reactions such as the one which takes place between catalase and hydrogen peroxide. In this reaction catalase decreases the activation energy and this means that more molecules make the activation boundary. However, catalase does this by binding with the hydrogen peroxide molecule into an ES complex. This reduces the amount of energy needed for the activation to happen. So my quantitative prediction is:

 

“At every ten degree increment up to the optimum the activation energy will be decreased by half [by the catalase], therefore doubling the amount of molecules attaining the activation energy and so doubling the overall rate of reaction.”

 

 

Graph showing my quantitative prediction:

 

GRAPH

 

THE END

 

 

IS THE ABOVE CORRECT.

What I don't understand is why enzymes lower the activation energy. Is what I've written about that correct?.

 

 

Please help me tie of all the lose ends. Corect all mistakes in the above etc.

 

ITS DUE IN ON WEDNESDAY 15TH JUNE 2005

 

So HELP!.

 

 

(all theory is based on going to the site http://www.s-cool.co.uk and going to A-level chemistry - reaction kinetics - affect of temperatue on rate.

 

(Bear in mind - I'm a GCSE student doing higher double science).

[5614]

Is that the Plan or the whole thing or what?

 

When I did mine I used distinct P, O, E & A sections, and although there was minor repetition it seemed to work out quite well, if you look at this site: http://www.8886.co.uk/ and follow the P or O or E or A links at the top there are bullet points of everything that needs to be included... make sure to include ALL points (where applicable,) because the marking system works whereby if you have levels 8 stuff but you do NOT have level 6 stuff you cannot score higher than 6... start off with the total basics just to make sure, then work progressively higher.

[Cloud]

It does say at the top in CAPITALS

 

It a QUANTITATIVE PREDICTION -(just after the prediction).

 

(which means it in the planning section) or P.

 

(I've completed O and E properly. Since most of P and A are the same (and have the most marks) - I need this theory right.

 

(YOU say you're not good at biology.) - (well most of this quantitave work is chemisty anyway - (biochemistry to be exact).

 

IS IT CORRECT from your knowledge of chemistry.

[Yggdrasil]

To understand this question, you need to understand not just the chemistry (all you wrote about the 10-degree rule is correct), but the biochemistry as well (this part is missing in your explanation). The 10-degree rule does not generally apply to reactions catalyzed by biological catalysts. Why? Enzymes are proteins with highly ordered three dimensional structures. Enzymatic catalysis depends upon the highly orderd structure of the molecule. These structures are held together by a wide variety of intramolecular forces ranging from very strong covalent interactions (such as disulfide bonds) to weaker interactions (such as hydrogen bonds or van der waals forces). So, in answering the question, you need to also think of the effects that raising the temperature would have on the catalyst.