3.1.4.2 Flashcards
What are enzymes used for?
Act as catalysts in reactions in biological systems by lowering activation energy
What type of molecule are enzymes made of?
Globular proteins
How much can enzymes increase the rate of reaction by?
Up to 10^20
How do enzymes catalyse reactions?
Provide an alternative reaction pathway which lowers activation energy
How do enzymes catalyse reactions?
-have a specifically shaped active site
-active site is complementary shape to substrate molecule
-upon collision an enzyme-substrate complex is formed
-this lowers the activation energy required for the reaction to proceed
-the products (now a different shape to the active site) are released
Describe the structure of an enzyme.
-the tertiary structure of the protein dictates the shape of the active site and therefore the action of the enzyme
-any deviation in DNA sequence may lead to a different sequence of amino acids in the primary structure which would alter the secondary and tertiary structure
Describe the induced fit model.
-substrate binds to active site
-induces the enzyme to change shape so there is an exact fit once the substrate has bound
-reactions can only take place after induced fit has occurred
-this model takes into account that proteins have some three dimensional flexibility
Name the factors affecting rate of enzyme catalysed reactions.
-temperature
-pH
-enzyme concentration
-substrate concentration
-inhibitors
-activators
How does increasing temperature affect the rate of enzyme reaction?
-increasing temperature increases kinetic energy
-increases chance of a collision between enzyme and substrate
-more collisions in a set period of time
-increases rate of reaction
How does pH affect the rate of enzyme reaction?
Changing pH changes number of hydroxide and hydrogen ions surrounding the enzyme
They interact with the charges on the amino acids affecting ionic and hydrogen bonding
Results in changes to the tertiary structure changing the shape of the active site
Enzymes become denatured, lowering the rate of reaction
How does enzyme concentration affect the rate of enzyme reaction?
Increasing concentration of enzyme in a solution means there are more enzyme molecules available to catalyse the substrate in a given time
Increasing the rate of reaction
How does substrate concentration affect the rate of enzyme reaction?
Increasing substrate concentration increases number of substrate molecules available to form enzyme substrate complexes
Initially increases rate of reaction then plateaus as enzymes are all saturated
What are inhibitors and the types of inhibitors?
Substrates that directly or indirectly interfere with the function of the active site
Competitive - bind to active site
Non competitive - bind to the enzyme/ allosteric site
Describe the structure and function of competitive inhibitors.
Prevent enzyme substrate complexes being formed
Similar in shape to the usual substrate
Affect active site directly - blocking access to enzyme substrate complexes
Increasing substrate concentration can compensate for the effects of non competitive inhibitors
No permanent damage to active site - reversible
Describe the structure and function of non competitive inhibitors.
Some non competitive inhibitors have a reversible effect, others denature the enzyme
Bind to another part of the enzyme, changing the shape of the active site
Substrate cannot bind to the active site - induced fit is prevented
