Enzymes Flashcards
What are enzymes?
Enzymes are catalysts that increase reaction rates without being used up in the reaction. Most enzymes are required in very small quantities. Most enzymes are globular proteins. However, some RNA (ribozymes and ribosomal RNA) also catalyze reactions.
What is a holoenzyme?
A holoenzyme is an apoenzyme (protein component of an enzyme) plus its cofactor/coenzyme
What are the advantages of biocatalysts over inorganic catalysts?
●Greater reaction specificity: avoids side products. The enzymes will choose the one most favourable, which results in less side products or wastes.
●ENzymes function better in the mild conditions of the cell. The pH of 7, temp of 37C and pressure of 1 atm
●Higher reaction rates: Enzymes increase reaction rates, so they can occur within an appropriate biological timeframe.
●Capacity for regulation: Enzymes can regulate their activity, whivh allows for precise control over biological pathways.
What is Enzyme substrate selectivity?
The enzyme’s ability to bind to a specific substrate
How do enzymes affect reaction equilibrium and free energy?
Enzymes do not affect equilibrium (Keq) or the free energy of the reaction (ΔG).
How do enzymes increase reaction rates?
Enzymes increase reaction rates (k) by decreasing the activation energy barrier (ΔG‡)
What is the relationship between spontaneous reactions and instantaneous reactions?
Spontaneous reactions (negative ΔG’°) are not necessarily instantaneous (or very fast). The rate or speed of the reaction is determined by overcoming the activation energy barrier (ΔG‡).
Why is the substrate selectivity of enzymes important?
It allows enzymes to only catalyse reactions that are necessary, so there aren’t any unwanted metabolic processes.
It is also important for drug development. It makes it easier to develope drugs that target specific enzymes. Exampe: HIV protease inhibiters block the HIV protease enzyme from cleaving viral proteins, hindering the viruses ability to multiply.
What are the binding pockets and active site?
The binding pocket is a broader portion on the enzyme’s surface where the substrate binds.
The active site is a smaller region in the binding pocket that contains the amino acids responsible for catalyzing the substrate.
What is the difference between the transition state and the intermediate states?
The transition state is represented by a peak on the reaction coordinate. The intermiediate is represented by a vally. The transition state is very unstable, transient and high energy. The intermediate state is more stable than the transition state, may be able to be isolated, but is less stable that the reactants or products
What is the difference between Gibbs free energy of activation and standard free enegy change?
Activation energy is the energy a reaction needs to occur or proceed. It is a kinetic factor and determines the rate of the reaction (how slow or fast it is). It is the reason the reaction doesn’t occur instantly.
The standardv free energy change is the change in free energy that occurs when a reaction is carried out under standrd conditions. It isn’t effected by an enzyme like the activation energy is. It tells us about the OVERALL free energy change.
Describe the ES.
It is the enzyme substrate complex. It forms when the enzyme binds to the substrate. 1st step in catalyztic process.
Describe the EP
Enzyme product complex.
forms after enzyme catalyzes the reaction. Product is still bound to the enzyme.
How much can an enzyme accelerate a reaction rate?
boosting them by a factor of 10^5 to 10^17.
example is orotidine monophosphate decarboxylase is a key enzyme in nucleotide biosynthesis. It increased reaction rate by a factor of 10^17
