MCBM Enzymes Lecture with Complete
Solutions
What is an enzymes role in a biological sense? - ANSWER - To act as a molecular catalyst
What class of molecule are MOST enzymes? - ANSWER - Proteins
Are enzymes affected by the reactions they catalyze? - ANSWER - No!
Where do substrates bind on enzymes? - ANSWER - The active site
Can any enzyme bind to any substrate? - ANSWER - No! Enzymes are highly specific and will
not take just any substrate
What are cofactors and why are they important? - ANSWER - Cofactors are additional
molecules that are required for catalysis of a reaction to occur
What are some examples of cofactors? - ANSWER - Metal ions or vitamin derivatives
How do enzymes affect the energy of activation of a reaction? - ANSWER - Enzymes lower the
energy of activation of reactions
How do enzymes affect the equilibrium or deltaG of a reaction? - ANSWER - They don't!
What is a holoenzyme? - ANSWER - A complete, catalytically active enzyme
What is an apoenzyme? - ANSWER - The protein part of a holoenzyme
What is pellagra? - ANSWER - Disease caused by a lack of niacin (Vitamin B3)
, What happens to a person biologically when they are afflicted with pellagra? - ANSWER - Lack
of vitamin B3 = decreased nicotinamide adenine dinucleotide (NAD) and its phosphorylated
form (NADP), which are important cofactors for a variety of body processes
Explain the 3 basic steps of enzyme-catalyzed reactions? - ANSWER - 1. Enzyme binds the
substrate.
2. Enzyme acts catalytically upon the substrate and produces the product
3. The product is released, leaving behind an available enzyme
Describe catalysis by bond strain - ANSWER - By straining the substrates natural bonds, the
transition state is more easily achieved
Describe catalysis by proximity and orientation - ANSWER - Reactive groups are brought in
close proximity to one another to induce the transition state
Describe catalysis with acids an bases - ANSWER - Acid-base catalysis. The acids and bases
are used to help stabilize charges produced during biochemical reactions and prevents them
from reverting back to the reactants
What is activation energy? - ANSWER - The change in free energy required to convert a
molecule into its transition state of a reaction.
How does activation energy influence the rate of a reaction at any given temperature? -
ANSWER - A higher activation energy will result in a slower reaction rate. A lower activation
energy will result in a faster reaction rate
What do enzymes do in terms of activation energy? - ANSWER - Enzymes lower activation
energy
What is binding energy? - ANSWER - The sum of the energies released during substrate-active
site interaction
Describe the active site on an enzyme - ANSWER - Usually a cleft or crevice on a larger 3D
protein structure
Solutions
What is an enzymes role in a biological sense? - ANSWER - To act as a molecular catalyst
What class of molecule are MOST enzymes? - ANSWER - Proteins
Are enzymes affected by the reactions they catalyze? - ANSWER - No!
Where do substrates bind on enzymes? - ANSWER - The active site
Can any enzyme bind to any substrate? - ANSWER - No! Enzymes are highly specific and will
not take just any substrate
What are cofactors and why are they important? - ANSWER - Cofactors are additional
molecules that are required for catalysis of a reaction to occur
What are some examples of cofactors? - ANSWER - Metal ions or vitamin derivatives
How do enzymes affect the energy of activation of a reaction? - ANSWER - Enzymes lower the
energy of activation of reactions
How do enzymes affect the equilibrium or deltaG of a reaction? - ANSWER - They don't!
What is a holoenzyme? - ANSWER - A complete, catalytically active enzyme
What is an apoenzyme? - ANSWER - The protein part of a holoenzyme
What is pellagra? - ANSWER - Disease caused by a lack of niacin (Vitamin B3)
, What happens to a person biologically when they are afflicted with pellagra? - ANSWER - Lack
of vitamin B3 = decreased nicotinamide adenine dinucleotide (NAD) and its phosphorylated
form (NADP), which are important cofactors for a variety of body processes
Explain the 3 basic steps of enzyme-catalyzed reactions? - ANSWER - 1. Enzyme binds the
substrate.
2. Enzyme acts catalytically upon the substrate and produces the product
3. The product is released, leaving behind an available enzyme
Describe catalysis by bond strain - ANSWER - By straining the substrates natural bonds, the
transition state is more easily achieved
Describe catalysis by proximity and orientation - ANSWER - Reactive groups are brought in
close proximity to one another to induce the transition state
Describe catalysis with acids an bases - ANSWER - Acid-base catalysis. The acids and bases
are used to help stabilize charges produced during biochemical reactions and prevents them
from reverting back to the reactants
What is activation energy? - ANSWER - The change in free energy required to convert a
molecule into its transition state of a reaction.
How does activation energy influence the rate of a reaction at any given temperature? -
ANSWER - A higher activation energy will result in a slower reaction rate. A lower activation
energy will result in a faster reaction rate
What do enzymes do in terms of activation energy? - ANSWER - Enzymes lower activation
energy
What is binding energy? - ANSWER - The sum of the energies released during substrate-active
site interaction
Describe the active site on an enzyme - ANSWER - Usually a cleft or crevice on a larger 3D
protein structure
