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when do enzymes START to denature?
I'm asking this question because I read that enzymes DO NOT START to denature after the optimum temp.
so then when do they start to get denatured

BobbJo

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They start to denature after the optimum temperature

https://en.wikibooks.org/wiki/A-leve...dation/enzymes
https://pdst.ie/sites/default/files/Enzymes.pdf
"So why does the graph show the rate of reaction peak at 40c? After 40c, the bonds in the enzyme molecule begin to shake so violently that they begin to break, which causes the enzyme to lose it's shape, which changes the shape of the active site (so the substrate will no longer fit) and the enzyme is said to be denatured. The reason the rate of reaction does not immediately drop to 0 is that the enzyme slowly loses shape as the temperature increases, and so the substrate fits less well and eventually not at all, and so the catalysis does not occur. The process of denaturing is usually irreversible.

In humans 40c is the optimum temperature for enzyme reactions- the temperature at which an enzyme catalyses a reaction at the maximum rate. We keep our bodies at 37c to make sure we never go above 40c as enzymes would start to denature at even the slightest upward variation - which would be extremely dangerous as nearly all reactions within the body rely on enzymes."

MARYAM1234567

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(Original post by BobbJo)
They start to denature after the optimum temperature

https://en.wikibooks.org/wiki/A-leve...dation/enzymes
https://pdst.ie/sites/default/files/Enzymes.pdf
"So why does the graph show the rate of reaction peak at 40c? After 40c, the bonds in the enzyme molecule begin to shake so violently that they begin to break, which causes the enzyme to lose it's shape, which changes the shape of the active site (so the substrate will no longer fit) and the enzyme is said to be denatured. The reason the rate of reaction does not immediately drop to 0 is that the enzyme slowly loses shape as the temperature increases, and so the substrate fits less well and eventually not at all, and so the catalysis does not occur. The process of denaturing is usually irreversible.

In humans 40c is the optimum temperature for enzyme reactions- the temperature at which an enzyme catalyses a reaction at the maximum rate. We keep our bodies at 37c to make sure we never go above 40c as enzymes would start to denature at even the slightest upward variation - which would be extremely dangerous as nearly all reactions within the body rely on enzymes."

https://qualifications.pearson.com/c...f_20140306.pdf
check page 9 of this document the paragraph below q4(not the student answer)

MARYAM1234567

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is it like it slowly keeps on losing shape as the temp increases and finally when no more substrate can fit
oh yeah, I get it as you said..that's why the rate doesn't immediately drop to 0 becuase they denature over time not immediately ohh ok!
thanks..i get it!!

BobbJo

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(Original post by MARYAM1234567)
https://qualifications.pearson.com/c...f_20140306.pdf
check page 9 of this document the paragraph below q4(not the student answer)

http://www.rsc.org/Education/Teacher...fb/enzymes.htm
"Above this temperature the enzyme structure begins to break down (denature) since at higher temperatures intra- and intermolecular bonds are broken as the enzyme molecules gain even more kinetic energy."

Bonds holding the enzyme begin to break and catalytic ability decreases until shape completely changes so no more catalysis occurs

Not sure what they mean "students tend to think that denaturation of enzymes only starts at temperatures above the optimum temperature". What do marking schemes write?

MARYAM1234567

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i think maybe they mean that students think that after the optimum temp the enzymes is completely denatured and no more substrates can fit when in actual denaturing occurs over a period of time
this is the question paper https://pmt.physicsandmathstutor.com...%20A-level.pdf

this is the answer to Q4 b)
1. idea that enzyme activity increases up to 60oC and then
drops ;
2. idea of increase in temperature results in increase in
kinetic energy ;
3. resulting in more {collisions / energetic collisions} /
enzyme-substrate complexes / eq} ;
4. idea that enzyme is denaturing (above 60°C) ;
5. due to {vibrations of within the enzyme / bonds changing
/ eq} ;
6. credit manipulation of figures e.g. 30 to 60°C increases
by
55 a.u. ;

MARYAM1234567

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they say this in the marking scheme for point 4
4. idea that enzyme is denaturing (above 60°C)
and then in the additional comment column, they say
4. NOT idea that enzyme starts to denature at 60°C

Bio 7

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Generally at 60 degrees centigrade but the can have different optimum temps so different denaturing points.

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MARYAM1234567

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(Original post by Bio 7)
Generally at 60 degrees centigrade but the can have different optimum temps so different denaturing points.

i don't understand

Bio 7

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#10

(Original post by MARYAM1234567)
i don't understand

Don’t understand what about 60 degrees?

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BobbJo

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#11

(Original post by MARYAM1234567)
i think maybe they mean that students think that after the optimum temp the enzymes is completely denatured and no more substrates can fit when in actual denaturing occurs over a period of time
this is the question paper https://pmt.physicsandmathstutor.com...%20A-level.pdf

this is the answer to Q4 b)
1. idea that enzyme activity increases up to 60oC and then
drops ;
2. idea of increase in temperature results in increase in
kinetic energy ;
3. resulting in more {collisions / energetic collisions} /
enzyme-substrate complexes / eq} ;
4. idea that enzyme is denaturing (above 60°C) ;
5. due to {vibrations of within the enzyme / bonds changing
/ eq} ;
6. credit manipulation of figures e.g. 30 to 60°C increases
by
55 a.u. ;

Yeah I think that's the idea they were looking for since the data in the table shows rather high activity (52au at 80 deg C) after the optimum.

[Note: The process of denaturing is gradual and partial denaturation exists.]

I think a safe way to write this marking point in the exam is
"Beyond the optimum temperature (60 degrees C), rate decreases as the enzyme starts to denature. Bonds holding the bulk of the enzyme vibrate and break. Tertiary structure of the enzyme is lost, etc"

I think the idea required is denaturing starts to occur above the optimum, not at the optimum

MARYAM1234567

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(Original post by BobbJo)
Yeah I think that's the idea they were looking for since the data in the table shows rather high activity (52au at 80 deg C) after the optimum.

[Note: The process of denaturing is gradual and partial denaturation exists.]

I think a safe way to write this marking point in the exam is
"Beyond the optimum temperature (60 degrees C), rate decreases as the enzyme starts to denature. Bonds holding the bulk of the enzyme vibrate and break. Tertiary structure of the enzyme is lost, etc"

I think the idea required is denaturing starts to occur above the optimum, not at the optimum

yes..i confirmed this with my supervisor.she said the same

MARYAM1234567

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thanks so much for helping out

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