Enzyme Action Flashcards
Thursday 12th September 2019
What does denatured mean? What causes it?
When the shape of an enzyme is changed so that its substrate no longer fits in the active site, so it can’t be broken down into its products.
Caused by - temperature over 37C, pH over
What is a model?
A visual representation of an idea - normally simple. An example - he lock & key model
What causes an enzyme to denature?
Temperature (over 37C) or pH
What do catalysts such as enzymes do?
Reduce the activation energy needed for a reaction. This means more collisions will be successful and end in a reaction
The substrate is
a) complementary
b) complimentary
to an enzyme’s active site (lock and key)
a) complEmentary
Why doesn’t the lock & key model work? (1894)
What stops the substrate from falling out of the enzyme-substrate complex?
Talk about the Induced Fit hypothesis (1958. Daniel Koshland)
The substrate isn’t 100% complementary first. It goes into the enzyme’s active site, and the enzyme moulds slightly around it
Really weak - hydrogen bonds, ionic attractions, van de Waals forces & hydrophobic interactions - non covelant forces. These bond the substrate to the active site.
When the product is formed, slightly different shape to the substrate, so it detaches from the active site
Enzyme + substrate –> Enzyme-substrate –> Enzyme-product complex –> enzyme + products
What are the bonds between an enzyme and the substrate in induced fit hypothesis?
really weak - hydrogen bonds, ionic attractions, van de Waals forces & hydrophobic interactions - non covelant forces
Give the word equation for
a) Lock & key hypothesis
b) Induced fit hypothesis
a) Enzyme + substrate –> enzyme-substrate complex –> enzyme + products
b) Enzyme + substrate –> Enzyme-substrate –> Enzyme-product complex –> enzyme + products
What is the difference between an enzyme-substrate complex & an enzyme-product complex?
An enzyme-substrate complex has no bonds connecting the 2 at all (lock & key), as it fits perfectly/ are complementary. An enzyme-product complex used to have bonds fitting the 2, but now the products are a different shape to the enzyme’s active site, so there are no bonds between the 2
If the active site can mould to fit a substrate, why does the body need different types of enzymes - wouldn’t the same one work for all substrates?
The enzyme can only change a little bit. However, some enzymes can break down more than one substrate if they have similar shapes
When asked to find a rate of reaction on a graph, what do you do if asked:
a) What’s the ROR at 20 seconds?
b) What’s the ROR across the first 20 seconds?
a) Draw a tangent. One Point, One Line!
b) Gradient
When proteins are heated to a high temperature, their tertiary structure is disrupted. Explain how this occurs (3 marks)
1) Weak hydrogen bonds are broken (made in tertiary structrue)
2) Protein unfolds
3) Change in the 3D shape, so the enzyme has denatured
At what temperature is the optimum for enzymes?
37C (same as internal temperature of humans. Coincidence? no, definitely not)>
Why does increasing the temperature increase the rate of a enzyme based reaction?
The substrate & enzyme molecules have more kinetic energy. So, they can move more and faster, leading to more frequent collisions, so more are successful.
More enzyme-substrate complexes, so faster ROR
