biochem exam 3
The most common ending for the name of an enzyme is _____
-ase.
For an enzyme-catalyzed reaction, the initial velocity was determined at two different concentrations of the substrate. Which of the following would be closest to the value of Km? [S] (mM) = 1.0, 4.0 Vo(mM/min) = 2.0, 2.8 A) 0.17 mM B) 5.7 mM C) 2.7 mM D) 0.60 mM E) 1.7 mM
0.60 mM
If the rate constant for the enzyme catalyzed reaction is 2e5 /sec and the rate constant for the uncatalyzed reaction is 2 e−6 /sec, the catalytic power of the enzyme is:
1e11
In Enzyme nomenclature, how many classes of enzyme are there?
6
What is the best description of how an enzyme can lower the activation entropy of a reaction through approximation?
An enzyme binds two substrates in the active site before the reaction.
Enzymes are proteins that function as catalysts for biological reactions. After formation of the enzyme-substrate complex, the enzyme catalyzes a chemical reaction. The new product(s) bound to the enzyme form a ________.
Enzyme-product complex
How can you find the Michaelis constant, Km, from a saturation plot?
It is the substrate concentration at 1/2 Vmax.
Which of the following does the concentration of enzyme not change?
Km
Which of the following is a cofactor? A) sucrose B) sucrase C) tryptophan D) NAD⁺ E) cholesterol
NAD⁺
The Michaelis constant, Km, provides information about the binding of the substrate to the enzyme. What does a low Km value mean?
The enzyme has a very high affinity for the substrate.
How does an enzyme catalyze a reaction?
The enzyme provides an alternative pathway for the reaction that has a lower activation barrier.
Enzymes are proteins that function as catalysts for biological reactions. When a substrate binds to the active site, the new temporary association is called the enzyme-substrate complex. The induced-fit model for binding states that...
a change in the shape of the enzyme occurs after the substrate binds that provides a complementary shape and strong electrostatic interactions
Which term describes the compound that the enzyme normally binds? The enzyme then catalyzes a reaction on this compound.
a substrate
The substrate binds to the ________ of an enzyme.
active site
What is the name for the region of an enzyme where binding of substrates occurs?
active site
What kind of inhibitor is Malonic acid with respect to Succinate Dehydrogenase?
competitive
Of the following, which name indicates an enzyme? A) lactoferrin B) 2-arachidonoyl glycerol C) palmitoylethanolamide D) diacylglycerol lipase E) anandamide
diacylglycerol lipase
What is the name of the irreversible inhibitor (drug) used as an example in the lecture?
disulfiram
As substrate concentrations increase, enzyme reaction rates ____. However, as substrate concentration becomes very high, enzyme reaction rates ______.
increase; plateau
Enzymes are proteins that function as catalysts for biological reactions. After the enzyme catalyzes the reaction, it releases the product(s) allowing the enzyme to repeat the reaction with a new substrate. The rate of a chemical reaction _______ as the substrate concentration increases. However, enzymes reach a maximum reaction rate when the substrate concentration is high. The substrate concentration at the maximum reaction rate is called ______.
increases; saturation
What model describes the readjusting of the enzyme shape to adapt to the shape of the substrate?
induced fit
Two enzymes with the same function but different structures and different Km values are called:
isozymes
Choose the best definition of catalytic efficiency.
kcat/Km
Enzymes are generally what type of biomolecule
protein
Enzymes are biological catalysts; they perform reactions in the cells. Enzymes are always what category of biomolecules?
proteins
When substrate concentrations are very high, the enzyme reaches its maximum turnover rate. The enzyme active sites are all filled with substrate and the enzyme is considered to be at _______.
saturation
The reactant in an enzyme-catalyzed reaction is known as the _____.
substrate
Enzymes are proteins that function as catalysts for biological reactions. The natural reactant molecules for a protein enzyme are called
substrates
Enzymes are proteins that function as catalysts for biological reactions. Substrates bind to the active site of an enzyme. Enzymes then catalyze reactions on the substrate molecules. Substrates bind to an active site of an enzyme. After the substrate-complex is formed, the enzyme can catalyze a reaction. Choose the best description of how the substrate binds to an enzyme.
temporary association facilitated by intermolecular attractions
An enzymatic reaction has a Vmax of 30 μM/min and a Km of 50 μM. If the concentration of the substrate is 25 μM, what will the velocity be?
the velocity will be 10 μM/min
What is the term used for the high-energy species that is formed along the pathway of the enzyme-catalyzed conversion of substrate to product?
transition state
In transforming the Michaelis-Menten equation into a straight line equation, y = mx + b, the Lineweaver-Burk double reciprocal plot, which of the following is NOT a true representation? A) slope = Km/Vmax B) y-intercept is 1/Vmax C) x-intercept is 1/Km D) y= 1/V E) x=1/[S]
x-intercept is 1/Km
When every enzyme molecule in the reaction mixture has its substrate-binding site occupied by substrate, the kinetics become ____-order, and the velocity is ____.
zero; Vmax
Under which condition are the enzyme kinetics zero order?
[S] > Km
