Enzymes Flashcards
What are enzymes?
Biological catalysts that speed up chemical reactions
Substrate
A molecule that bonds to the active site of an enzyme to be catalysed by it in a reaction
Structure of an enzyme: active site
The tertiary structure of its protein(s) fold into the specific shape
Which determines the active site where substrate binds to because they are SIMILAR (not the same) in shape
Enzyme substrate complex
When the substrate is bonded to the active site of an enzyme forming this
How do enzyme substrate complexes form?
When the substrate and enzyme’s active site collide successfully
Because the active site is complementary to substrate after changing tertiary structure in induced fit model
So forms complex
Products
What is a product of the enzyme catalysed reaction eg proteins being broken down to amino acids
What is the job of enzymes?
To increase rate of a reaction
Because it’s a biological catalyst
How do enzymes increase rate of reaction?
When an enzyme-substrate complex is formed the substrate bonds are put under stress
Causing the activation energy of this catalysed reaction to lower (energy required to break bonds in substrate) so reaction is more likely to occur
What is the induced fit model?
Explains how an enzyme’s active site can bond to a substrate
Because they are complementary to each other however the active site has to mould itself
Description of the induced fit model in action
Substrate moves towards enzyme’ active site, and fits inside because they are SIMILAR in shape
The active site changes shape so it can be complementary to substrate and bind to form an enzyme-substrate complex (puts bonds under stress in substrate)
Why do only substrate molecules cause the enzyme’s active site to distort?
Because the bonds between amino acids in the active site of the enzyme and the substrate won’t be formed so the shape of the tertiary structure won’t change
What was the original theory for how enzymes are complementary to substrates?
The lock and key theory which said all enzymes active sites are already complementary to the substrates
A product time graph
Tells us the amount of product produced over the course of an enzyme catalysed reaction
Could be under certain conditions such as increased temperature etc
Description of a product/ substrate time graph for an enzyme catalysed reaction
Initially rapid because there is a high concentration of substrate molecules thus more enzyme substrate complexes
Decreasing rate of reaction in middle because no. Of substrate molecules is decreasing as more is made to products so lower rate of reaction (less enzyme substrate complexes formed)
Plateaus because no more substrate molecules collide with active site = stopped
How to find rate of reaction at a specific point on a product/substrate time graph?
Draw tangent at that point
What’s important to remember about finding the rate of reaction at a specific point using a tangent?
Can only be done on a product time graph
Because some graphs already have rate of reaction on the y axis so simply use the y axis
What factors affect enzyme catalysed reaction?
Temperature
Substrate/ enzyme concentration
pH
Competitive/ non competitive inhibitors
How to describe the factors effect on INCREASING enzymes rate of reaction?
This factors causes ____
Which increases frequency of successful collisions between enzyme’s active site and substrate because ____
So number of enzyme-substrate complexes formed increase
Therefore more products are formed in a given time, increases rate of reaction
How to describe the factors effect on DECREASING enzymes rate of reaction?
This factor causes _____
Which decreases the frequency of successful collisions between enzyme and substrate because _____
So number of enzyme-substrate complexes formed decrease
So less products formed in a given time, decreasing rate of reaction
