Enzymes Flashcards
What is the definition of an enzyme
A biological catalyst
What do catalysts do
They increase the rate of reaction without being used up
How do enzymes increase the rate of reaction
They do this by decreasing the amount of activation energy that is required for a reaction to take place, so more molecules have the activation energy or more allowing them to react.
What is an example of an intracellular enzyme and what does it do
Catalase binds to H2O2 also known as hydrogen peroxide and catalyses it’s breakdown into water and oxygen
What is an example of an extracellular enzyme
Amylase which is produced in the pancreas and released into the small intestine, catalysing the breakdown of starch into maltose.
What is the molecule that binds to the enzyme called
It is called the substrate molecule
What are the molecules that are produced called
The products
What is the active site
The active site is where the substrate binds to
When the enzyme binds to the substrate what is it called
An enzyme substrate complex
What is the substrate in relationship to the active site
The active site is complementary to the substrate
What does the complementary nature mean
Each enzyme is specific to the substrate molecule it binds to
What happens once the substrate binds to the active site
Amino acids on the active site can form temporary bonds with the substrate molecule
What happens to molecules that aren’t complementary
It will not be able to bind to the active site
What happens once the reaction is catalysed
A product complex is formed and then the product is released from the active site
What are catabolic enzymes
enzymes that can break down larger molecules into smaller molecules
What are anabolic enzymes
Enzymes that can build up larger molecules from smaller molecules
What is the lock and key model
The substrate molecule fits perfectly into the active site similar to how a key fits into a lock. Furthermore, only one key can fit into the lock demonstrating the highly specific nature of enzymes.
What is the induced fit model
The tertiary structure of the active site changes as the substrate approaches. As the substrate starts to form bonds with the active site, the active site undergoes a conformational change so that the active site moulds around the substrate. The conformational change allows the active site to perfectly fit the substrate
How does the induced fit model show enzyme specificity
Molecules that aren’t the substrate can;t form the correct bonds to the correct amino acids in the active site. So the structure of the enzyme doesn’t adjust to fit the molecule.
What are cofactors
Most enzymes require accessory compounds in order to be functional. These are called cofactors.
If a cofactor is organic what is it called
It is called a coenzyme
What are inorganic cofactors normally and give an example
Inorganic cofactors are normally ions such as zinc or chloride. And an example is chloride ions are a cofactor for amylase.
What does chloride do to amylase
They held maintain the shape of the active site of the amylose molecule, which ensures that the active site is properly configured for breaking down starch.
What is the difference between prosthetic groups and other cofactors
Whereas other cofactors are loosely or temporary bound to the enzyme, prosthetic groups are tightly bound forming a permanent feature of it.
What are vitamins a source of
They are a source of coenzymes for many enzymes in organisms.
What is an example of a vitamin as a coenzyme and what does it do
Vitamin B5: which is crucial for the synthesis and oxidation of fatty acids and in the Krabs cycle.
What are the two types of inhibition
Competitive inhibition and non-competitive inhibition
What is the shape of a competitive inhibitor
It is a molecule or part of a molecule that has a similar shape to the substrate of an enzyme and can fit into the active site of the enzyme
What do competitive inhibitors do
They block the substrate from entering the active site preventing the enzyme from catalysing the reaction. Therefore the enzyme can’t carry out its functions and is inhibited.
What is the inhibitor
The non-substrate molecule that binds to the active site
What do substrate and inhibitor molecule do with each other
They compete with each other to bind to the active site of the enzymes.
What does the competition between substrate and competitive inhibitor molecules do
It reduces the number of enzyme-substrate complexes that form and slows down the rate of reaction.
What are the 3 factors that affect competitive inhibition and the amount of inhibition?
Relative concentration of substrate, inhibitor and enzyme.
What do the majority of competitive inhibitors do and what does the minority do
They bind temporarily to the active site of the enzyme, so their effect is reversible. However, some bind irreversibly to the active site so their effects can’t be reversed by increases in substrate concentration.
What is non competitive inhibition
It is where the inhibitor binds to the enzyme at a location other than the active site. This alternative site is called an allosteric site.
What does the binding of the non competitive inhibitors do
it causes the tertiary structure to change meaning the active site changes shape. This results in the active site no longer having a complementary shape to the substrate so it is unable to bind to the enzyme.
What happens to the enzyme as a result of the inhibition
it can’t carry out its functions and nis said to be inhibited
What does the inhibitor involved in non-competitive inhibition do (why is it called non-competitive inhibition)
It does not compete with the substrate for the active site and it is therefore called non-competitive inhibition.
What is a factor that will not overcome the effect of non competitive inhibition and a factor that will increase or decrease it
Increasing the concentration of an enzyme or substrate will not overcome the effect of non-competitive inhibition. However, increasing the concentration of the inhibitor will decrease the rate of reaction further.
What is end product inhibition
when the product of a reaction acts as an inhibitor to the enzyme that produces it.
What does end product inhibition allow for
A negative feedback control mechanism
What is the difference between irreversible and reversible non-competitive inhibition
Irreversible inhibitors can’t be removed from the allosteric site of the enzyme whereas reversible inhibitors can.
How can you measure the rate of reaction of enzyme controlled reactions
By drawing a tangent to the curve at that point. The gradient of the tangent can then be calculated to work out the rate of reaction.
What does the rate of an enzyme controlled reaction depend on
It depends on the frequency of successful collisions between the substrate molecules and the active site.
Sketch the graph for amount of product and time of an enzyme controlled reaction
Explain the different stages of the graph (beginning)
At the beginning, there are a large amount of substrate molecules that are present. Resulting in a high frequency of successful collisions between the substrate molecules and active site so the rate of reaction is very high
Explain the different stages of the graph (middle)
As the reaction takes place some of the substrate is converted to product. Resulting in a decrease in the amount of substrate molecules. So there is a decrease in the frequency of successful collisions between the substrate and active site, so the rate of reaction decreases.
Explain the different stages of the graph (end)
At the end all of the substrate molecules have been converted to the product, so the reaction has stopped.
What is the equation for the temperature coefficient
Temperature coefficient = rate of reaction at temperature X + 10*c/ rate of reaction at temperature X
Sketch the graph for temperature and rate of reaction of enzyme controlled reactions
Why does the rate of reaction increase until the optimum temperature
The rate of reaction increases as we are increasing the kinetic energy of the enzyme and the substrate. As they are moving quicker, the probability of the substrate colliding with the active site increases. This increases the frequency of collisions between the substrate and active site causing the rate of reaction to increase.
What occurs at the optimum temperature and what does it mean
The rate of reaction is at its highest, which means that there is the maximum frequency of collisions between the substrate and the active site.
What is the optimum temperature normally around
40*C
Explain what happens to the rate of reaction past the optimum temperature
The rate of reaction decreases. This is because at higher temperatures the enzymes and vibrating rapidly. These vibrations cause bonds within the enzymes such as hydrogen bonds to break. As a result, the tertiary structure of the enzyme begins to change, resulting in the shape of the active site changing, and it results in it no longer being complementary to the substrate, so it can;t fit in it and now the enzyme is denatures and doesn’t function normally any more.
What is a feature of denaturation
Once denatured due to high temperatures they can’t renature when cooled down. As its tertiary structure has changed so much that it can’t be reversed.
What does the PH of a solution depend on
The concentration of hydrogen H+ ions
What do each enzymes work best at and what do changes do
The work fastest at a specific optimum PH. If the PH changes away from the optimum PH< then the rate of reaction decreases.
What can the hydrogen ions do (1)
Bond with the R groups on the amino acids in the enzyme. this includes amino acids in the active site which can form temporary bonds to the substrate. This can prevent the R groups from bonding with the substrates which reduces how effectively the substrate binds to the active site reducing the rate of reaction.
What can the hydrogen ions do (2)
They can also bond with R groups in the rest of the enzyme molecule, this can break the bonds holding the tertiary structure of the enzyme in place. Which can change the shape of the active site making it less likely that the substrate can attach successfully. If the PH changes significantly the active site may change shape so that it’s no longer complementary to the substrate so has denatured.
Sketch the graph of PH and rate of reaction and show the optimum PH
How does substrate concentration affect enzyme controlled reactions
As the concentration of a substrate is increased, the number of substrate molecules increases. The increased number of substrate particles leads to a higher collision rate and the formation of more enzyme substrate complexes so the rate of reaction therefore increases. It will increase up to its maximum. At this point all of the active sites are occupied by a substrate molecule and no more enzyme-substrate complexes can be formed until the products are released.
Sketch a graph for rate of reaction and concentration of substrate
What is the relationship between concentration of enzymes and rate of reaction
As the concentration of enzymes increases, the number of available active sites in a particular area increases, which results in more enzyme-substrate complexes forming at an increased rate.
What does the rate of reaction increase to in enzyme concnetration
It increases until the maximum where the substrate concentration becomes the limiting factor and the rate of reaction decreases as all the substrate is used up.
