Enzymes Flashcards
What do enzymes do to reactions
Catalyse them
Are enzymes globular or fibrous proteins
Globular
What is meant by the specificity of enzymes
Which biochemical reaction is catalysed by the enzyme
What are anabolic reactions
Where smaller molecules are joined together to make a larger one
What are catabolic reactions
Where larger molecules are broken down to form smaller ones
Which out of anabolic and catabolic reactions are catalysed by enzymes
Both
What is metabolism
Metabolism is the sum of all of the different reactions and reaction pathways happening in a cell or an organism, and it can only happen as a result of the control and order imposed by enzymes
What factors affect reaction rate
Temperature
Pressure
pH
What is Vmax of a reaction
The maximum rate of reaction
What is activation energy
The minimum amount of energy required for a reaction to occur
What are the 2 ways that enzymes reduce the required activation energy
Lock and key hypothesis
Induced-fit hypothesis
What is formed when enzymes and substrates join together
An enzyme-substrate complex
What do intracellular enzymes do
aid metabolic processes inside of both prokaryotes and eukaryotes
An example of an intracellular enzyme and what it does
Catalase ensures that hydrogen peroxide is broken down into oxygen and water, therefore preventing its accumulation
What do extracellular enzymes do
Break down larger nutrient molecules into smaller molecules in the process of digestion
An example of an extracellular enzyme and what it does
Amylase begins the digestion of starch in the mouth
What does trypsin do
An enzyme that catalyses the digestion of proteins into smaller peptides which can then be broken down further by other proteases
What factors affect enzyme activity
Temperature
pH
Enzyme and substrate concentration
What is temperature coefficient (Q10)
A measure of how much the rate of reaction increases with a 10 degree rise in temperature
What is Q10 usually for an enzyme-controlled reaction
Usually around 2
How are enzymes working at colder temperatures adapted
They are more flexible, especially at the active site. However it makes them more vulnerable to smaller temperature changes
How are enzymes working at warmer temperatures adapted
The enzymes are more stable due to an increased number of bonds, particularly hydrogen and disulphide bonds
Why does pH affect the shape of enzymes
A change in the concentration of H+ ions and OH- ions interfere with the shape of the tertiary structure
Why is it important to control metabolic activity within cells
Important to regulate the rate and quantity of product formation
What effects does a competitive inhibitor have
Slows down the rate of reaction however does not impact the Vmax of a reaction
How can the effects of a competitive inhibitor be reduced
Add more substrate
What site does non-competitive inhibitors bind to
Allosteric site
How does a non-competitive inhibitor work
Binds to the allosteric site which causes the tertiary shape of the enzyme to change, therefore the shape of the active site changes
Example of irreversible non-competitive inhibitors
Proton pump inhibitors (PPIs) are used to treat long term indigestion. They irreversibly block an enzyme system responsible for secreting hydrogen ions into the stomach
What is end-product inhibition
When the product at the end of an enzyme-controlled reaction acts as an inhibitor to the enzyme that produces it
What kind of a feedback cycle is end-product inhibition
Negative feedback
What is an example of a reversible non-competitive inhibition
End-product inhibition
What is a cofactor
A cofactor is a substance that has to be present to ensure that an enzyme-catalysed reaction that takes place at the appropriate rate
What is a prosthetic group
Cofactors that are permanently bound to the protein
Example of a prosthetic group
Zn2+ ion in carbonic anhydrase, which is an enzyme necessary for the metabolism of carbon dioxide
Why can’t the inhibitor be removed easily in a non-competitive inhibition
Strong covalent bonds are formed
Why can the inhibitor be removed more easily in a competitive inhibition
Weaker hydrogen or ionic bonds are formed
What are inactive precursor enzymes
Enzymes that are produced in an inactive form
What often needs to change shape in precursor enzymes for them to be activated
Active site
How do precursor enzymes become activated
By the addition of a cofactor
What is a precursor enzyme called before a cofactor is added
Apoenzyme
What is a precursor enzyme called after a cofactor is added
Holoenzyme
