focus chapter 6 (enzymes) Flashcards
general properties of enzymes
o Biological catalysts
o Accelerate chemical reactions under physiological (mild) conditions
o Most are proteins
o Highly specific in their reaction and substrate
o Capacity for regulation
o Not changed or used up after a reaction
Oxidoreductases
Can catalyze oxidation/reduction reactions
Transfer electrons from one substance to another
Transferases
Transfer a functional group from one substance to another
Hydrolases
Help form two products through hydrolysis
Lyases
Non-hydrolytic addition or removal of groups from substrate
Isomerases
Intramolecule rearrangement (isomerization)
Ligases
New bonds with simultaneous breakdown of ATP
Translocases
Catalyze the movement of ions or molecules across membranes of their separation within membranes
Exergonic reactions have a
negative ΔG (free energy is released)…favorable
are endergonic or exergonic reactions favorable
exergonic
Endergonic reactions have a
positive ΔG (free energy input required)…unfavorable
A reaction is spontaneous if
change in G is less than 0
enzymes do not affect change in G
Thermodynamics
looks at standard free energy and tells you if the reaction will happen
kinetics
How fast a reaction is happening
Is effected by enzymes
energy diagrams of enzyme catalyzed reactions
o X-axis is reaction progress
Time value
o Y-axis is free energy
It tells you if the reaction is exergonic or endergonic
o The difference in heigh from the substrates and the products is the change in G for the reaction
o Catalyzed before transition state and uncatalyzed after
transition state
A molecular form that is no longer substrate but not yet product
Enzymes facilitate the formation of
the transition state
Activation energy
the energy required to form the transition state from the substrate
Relate chemical kinetics to an understanding of how enzymes increase reaction rates
o Enzymes do not change the equilibrium of a reaction
o Enzymes decrease the activation energy, accelerating the reaction
o Enzymes decrease the time to reach the equilibrium
Lock and key model
Substrate must perfectly fit the enzyme
The induced fit model
When the substrate fits together with the enzyme, the enzyme itself will change to either join substrates together or break a substrate down
the two main models describing enzyme-substrate interactions
lock and key model and the induced fit model
key characteristics of enzyme active sites
o The active site is a three-dimensional cleft or crevice created by amino acids from different parts of the primary structure.
o The active site constitutes a small portion of the enzyme volume.
o Active sites create unique microenvironments.
o The interaction of the enzyme and substrate at the active site involves multiple weak interactions.
o Enzyme specificity depends on the molecular architecture at the active site.
Explain the relationship between the transition state and the active site of an enzyme.
o Transition states are unstable arrangement of atoms that cannot be isolated.
o Transition state analogs mimics this arrangement, inhibiting the enzyme.
o Enzymes prefer to bind the transition state, because it represents the highest energy with the best binding.
