Enzymes Flashcards
what do Oxidoreductases do ?
Transfer electrons
What type of enzyme forms isomers (transfers groups within a molecule) ?
Isomerase
What type of enzyme enables hydrolysis ?
Hydrolase
What type of enzyme forms double bonds & adds groups to double bonds ?
Lyase
What does Isomerase do ?
Forms isomers (transfers groups within a molecules)
What do ligases do ?
Forms bonds via ATP splitting
What type of enzyme forms bonds via ATP splitting ?
Ligases
What type of enzyme transfers electrons ?
Oxidoreductase
What is desolvation
Where an enzyme loses hydrogen bonds
What is induced fit ?
Where a protein changes shape to induce a lock & key formation & a conformational change takes place when the substrate binds
Define ∆H
Enthalpy change: Change in potential energy (∆H must be negative for a reaction to take place)
Define ∆S
Entropy change: Change in disorder, the more disordered the more likely the reaction.
Name 3 ways enzymes lower the activation energy ?
Decrease entropy: Particles more aligned and less energy is required to collide.
Desolvation: Where weak H bonds between enzyme & substrate are replaced by strong H bonds between substrate and aqueous soloution
Induced fit: conformational changes in enzyme allow enzyme and substrate to bind.
What is happening at V0 ?
The reaction is at a steady state (initial reaction velocity) & ES is stable
What is Vmax & what does it tell us about the reaction ?
Vmax is the maximum reaction velocity where the enzyme is saturated with substrate. Vmax tells us how fast the reaction is.
What is Km & how is it calculated ?
Km is Michaelis constant & is calculated as half of Vmax.
What does Km tell us about the reaction ?
High Km = Loose fit and unstable
Low Km = Tight fit and stable
Stability of ES complex
What is a non-competitive inhibitor ?
It binds to the enzyme but not at the active site.
What does a non-competitive inhibitor do to the Vmax and the Km ?
Vmax: Is decreased due to the binding & possible change of active site, reaction slowed.
Km: Unchanged as substrate can still bind to active site.
What is a competitive inhibitor ?
It binds to the active site on the enzyme
What does a competitive inhibitor do to the Vmax and the Km ?
Vmax: Unchanged as enzyme can overcome inhibition by increasing substrate inhibition.
Km: Increased, as the inhibitor does not fit the enzyme as tight as the substrate therefore high Km means loose fit and unstable.
What are the properties of Allosterically-regulated enzymes ?
Made up of many sub-units with many biding sites
Cooperatively bound
They are examples of non-competitive inhibitors
Bind to the enzyme and change the shape of binding site
What is a concerted model enzyme ?
Where binding to one active site opens up all active sites and allows S to bind more effectively
What is a sequential model enzyme ?
Where S binding to an active site only opens one active site a ta time in sequence.
What is a covalently-modified enzyme ?
They are reversible and have multiple phosphorylation sites allowing for fine tuning of enzyme function.
