lecture 9 - intro to enzymes Flashcards
How do enzymes catalyse thermodynamically favourable reactions?
By lowering the activation energy required
What is required for a reaction to reach a high-energy transition state?
Activation energy supplied
What is the activation energy, as read off a reaction progress graph?
The difference in energy between the reactants and the activated complex/transition state
How do enzymes influence forward and reverse reactions?
By decreasing activation energy, the forward and reverse reactions are accelerated equally
What is the symbol for change in free energy?
ΔG
What is the symbol for activation energy?
Ea OR ΔG‡
How does ΔG change when an enzyme is introduced to a reaction?
There is no change, only ΔG‡ decreases
What type of molecule makes up the majority of enzymes?
Proteins
What is the function of glycogen phosphorylase
An enzyme that aids in glycogenolysis - breaking highly branched glycogen into glucose monomers
What are the 6 main classes of enzymes?
Oxidoreductants, transferases, hydrolases, lyases, isomerases, ligases
What is the role of an oxidoreductant enzyme?
Facilitate redox reactions, with electron transfer
What is the role of a transferase enzyme?
Facilitate the transfer of functional groups
What is the role of a hydrolase enzyme?
Facilitate the hydrolysis/cleavage of molecules using H2O
What is the role of lyase enzymes?
Facilitate the Non-hydrolytic breaking or making of a bond
What is the role of isomerase enzymes?
facilitate the transfer of atoms/groups within a molecule to yield an isomeric form
What is the function of ligase enzymes?
Join 2 molecules together via the formation of a new bond. this is usually couple to ATP cleavage
Ligase enzyme reactions are usually coupled to what reaction?
ATP cleavage, which provides energy
What is a cofactor?
A non-protein compound or metal ion that is required for an enzyme’s catalysis
What are the 2 classes of cofactor?
Metal ions and coenzymes
What are metal ion cofactors?
Lewis acids (electron pair acceptors) that can participate in acid-base catalysis
Are metal ions Lewis Acids or Bases?
Lewis Acids (electron pair acceptors)
How do metal ions act as cofactors?
They form coordination compounds with precise geometries for positioning reactants exactly where they need to be.
What are some common examples of metal ion cofactors?
Mg2+, Zn2+, Fe2+/Fe3+
What are coenzymes?
Small organic molecules that act as cofactors/cosubstrates
How do coenzymes act as cofactors?
They are carriers of electrons, atoms or functional groups
What are coenzymes often derived from?
Vitamins
How do enzymes make reactions favourable via reaction coupling?
The coupling of a non-spontaneous and spontaneous reaction can result in an overall spontaneous reaction
where do cofactors bind?
the active site
What coenzyme facilitates glycogen phosphorylase activity by binding to the active site?
PLP - pyridoxal phosphate
