3. Which of these statements about enzyme-catalyzed reactions is false? | A) At
ID: 267847 • Letter: 3
Question
3. Which of these statements about enzyme-catalyzed reactions is false? | A) At saturating levels of substrate, the rate of an enzyme-catalyzed reaction is proportional to the enzyme concentration. B) If enough substrate is added, the normal Vmax of a reaction can be attained even in the presence of a competitive inhibitor. C) The rate of a reaction decreases steadily with time as substrate is depleted. D) The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, but the equilibrium constant is more favorable in the enzyme-catalyzed reaction. E) The Michaelis-Menten constant Km equals the [S] at which V = 1/2 Vmax. 4. When oxygen binds to a heme-containing protein, the two open coordination bonds of Feare occupied by: A) one O atom and one amino acid atom. B) one Oz molecule and one amino acid atom. C) one O2 molecule and one heme atom. D) two O atoms. E) two O2 molecules.Explanation / Answer
Answer: Option D.
The statement is false regarding Enzyme-catalyzed reaction is the activation energy for the catalyzed reaction is the same as an uncatalyzed reaction, but the equilibrium constant is more favorable in the enzyme-catalyzed reaction.
Catalyst: Substance which enhances the rate of a reaction without involving in the reaction is called Catalyst. By decreasing the activation energy, the rate of reaction increased.
Remaining options are true in respective situvations.
V=Vmax/2
Vmax/2= Vmax. [s]/ Km+[S]
1/2=[S]/ Km+[S]
Km+[S]=2[S]
Km=[S]
4) Option B
One oxygen molecule and one amino acid.
Heme contains a heterocyclic ring system called protoporphyrin ring, which forms the organic part of the molecule and an iron atom (Fe+2). The ring made up of with four pyrrole rings that get linked by methene bridges.
The Fe atom bind to 4 nitrogens in the center of protoporphyrin ring. Iron can form two additional bonds, on either side of Heme plane. These binding sides are termed as the 5th and 6th coordination positions.
In heme protein, the 5th position is occupied by the 1 Nitrogen atom from Histidine side chain.
6th position occupancy is depended,
If Ferro Hemoglobin: 6th position is occupied by O2 molecule (Oxygenated).
In Deoxygenated Ferri Hb: 6th position is empty.
Met Hb: 6th position is occupied by the H2O molecule.
From given options, we chose the One oxygen molecule and one amino acid.
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