1. __________________ refers to the process of separating or extracting the target compound from other compounds or contaminants.
a) Quantification of a compound
b) Identification of a compound
c) Purification of a compound
d) Chemical separations
Explanation: The process of separating or extracting the target compound from other compounds or contaminants is referred to as purification. Chromatography produces characteristic peaks for a specific compound. Hence the target compounds, contaminants and other compounds must have different peaks which means they must have different migration values so that the desired product may be eluted, and not the undesired ones.
2. The process of determining the unknown concentration of a compound in a known solution by using HPLC is referred to as _______________
a) quantification of a compound
b) purification of a compound
c) chemical separations
d) identification of a compound
Explanation: Quantification by using HPLC refers to the process of determining the unknown concentration of a compound in a known solution. It involves injection of series of known concentration of the standard solution onto HPLC. This is detected as series of peaks that is correlated to concentration of compound injected. By comparing the peak of unknown concentration these known peaks, the concentration can be quantified.
3. To alter the retention time, which of the following parameters need not be manipulated?
a) Choice of column
b) Choice of mobile phase
c) Choice in flow rate
d) Sample type
Explanation: Identification of a compound by using HPLC is done by using a detector. The detector identifies in the form of peaks. The identifying peak should have a reasonable retention time and should be well separated from other extraneous peaks at detection level. To alter the retention time, the parameters which can be manipulated are choice of column, mobile phase and flow rate. Sample type does not matter.
4. In HPLC, the compounds are eluted using a constant mobile phase composition and is referred to as _____________
a) nonspecific elution
b) isocratic elution
c) specific elution
d) gradient elution
Explanation: In isocratic elution, the compounds are eluted using a constant mobile phase composition. As compared to gradient elution in which the compounds are eluted using increasing strength of the organic solvent. Specific and nonspecific elution occurs during affinity chromatography. As compared gradient and isocratic elution which is taking place during HPLC.
5. In _________ elution, the compounds are eluted by increasing the strength of the organic solvent during HPLC.
a) nonspecific
b) gradient
c) specific
d) isocratic
Explanation: Specific and nonspecific elution occurs during affinity chromatography. Isocratic elution is one which the elution is done using a constant mobile phase. The process of eluting compounds during HPLC by increasing the strength of the organic solvent is referred to as gradient HPLC. The sample is injected on weaker mobile phase and the strength is increased in linear fashion by raising the organic solvent fraction which results in the elution of retained compounds.
6. The study of rates of chemical reactions that are catalyzed by enzymes is referred to as ______________
a) first order reaction kinetics
b) zero order reaction kinetics
c) chemical kinetics
d) enzyme kinetics
Explanation: Enzyme kinetics is referred to as the rates of chemical reactions that are catalyzed by enzymes. Whereas chemical kinetics describes the rates of chemical reactions. Zero order reaction kinetics is one in which the rate of the reaction does not depend on reaction concentration. Whereas first order reaction kinetics is one in which the rate of the reaction depends on molar concentration of one of the reactant.
7. Lock and key model was proposed by ______________ in 1890.
a) Henri
b) Miachelis and Menten
c) Emil Fischer
d) Daniel Koshland
Explanation: Lock and key model was proposed by Emil Fischer in 1890. Whereas Daniel Koshland proposed induced fit model in 1958. Henri in 1903 and Miachelis and Menten in 1913 proposed kinetic models for enzyme catalyzed reaction. The main difference is that Miachelis and Menten did a strong experimental work than Henri to prove that an enzyme catalyzing single substrate reaction will possess a hyperbolic curve.
8. The lock and key model deals with flexible nature of enzymes.
a) true
b) false
Explanation: The lock and key model proposes that as key fits into the model the substrate fits into the active site of the enzyme. This model doesn’t consider conformational changes during binding of substrate to its active site which is proved by X-ray diffraction and NMR. Thus the above statement is false. The model doesn’t deal with flexible nature of enzymes.
9. The target substrate molecules bind to active site of the enzyme transforming into products through a series of steps known as the ____________
a) enzyme kinetics
b) enzymatic mechanism
c) chemical kinetics
d) zero order reaction kinetics
Explanation: Enzymatic mechanism is referred to as series of steps through which products are formed when substrate molecule binds to active site of the enzyme. The rates of chemical reactions that are catalyzed by enzymes is called enzyme kinetics. Whereas chemical kinetics describes the rates of chemical reactions. Zero order reaction kinetics is one in which the rate of the reaction does not depend on reaction concentration.
10. When the free energy occurs at standard conditions, it is termed as ______________
a) Activation energy
b) pKa
c) Standard free energy change
d) Gibbs free energy
Explanation: Standard free energy change is referred to as the free energy change occurring at standard conditions, i.e., at 25°C, pH 7, 1 mol/L solute concentration and normal gas. Gibbs free energy is the energy that exist for performing work. Activation energy is the energy required to attain transition state. pKa is the pH at which half of the ions are ionized.