🧬 Biochemistry Solved MCQs with Answers

Practice 1490 approved 🧬 Biochemistry questions with verified answers from the 🧬 Medical Science subject for Pakistan exams.

1490 solved MCQs

How many possible orientations do spin 1/2 nuclei have when they are located in an applied magnetic field?Answer: 2 In immunofluroscence microscopy, fluroscent compounds are attached toAnswer: An antibody specific for the subcellular structure An FT-IR instrument record a signal in theAnswer: Time domain When radiation energy is absorbed by a spin 1/2 nucleus in a magnetic field, what happens?Answer: The angle of precession flips so that the magnetic moment of the nucleus opposes the applied field Negative staining is a technique used inAnswer: Electron microscopy What is the relationship between wavelength and wave number?Answer: Wavenumber = 1 / wavelength in centimeters In the intersystem crossingAnswer: The spin of an excited electron reverses, changing the state of the molecule (from singlet state to triplet state or vice versa) Why must the radiation source for fluorescence spectrometry be more powerful than for absorption spectroscopy?Answer: Because the magnitude of the output signal is proportional to the power of the incident radiation Why do fluorescence spectrometers often use double-beam optics?Answer: To compensate for power fluctuations in the radiation source For a molecule to absorb IR, why must the molecule's vibrations cause fluctuations in the dipole moment of the molecule?Answer: Because for absorption to occur, the radiation must interact with the electric field caused by changing dipole moment Internal conversion is whereAnswer: A molecule converts excess electronic energy to vibrational energy Why phosphorescence measurements are usually made at a low temperature?Answer: To promote phosphorescence by slowing the rate of radiationless transfer processes Fluorescence occurs whenAnswer: A molecule returns to the electronic ground state from an excited singlet state by losing it's excess energy as a photon What is shielding in NMR?Answer: When the magnetic moment of an atom blocks the full induced magnetic field from surrounding nuclei What is used to cool the superconducting coil?Answer: Liquid helium Coupling causes the peaks in ¹H NMR spectra to be split intoAnswer: Multiple peaks equal to the number of hydrogen on surrounding atoms, plus one When placed in a magnetic field, all the random spins of the nucleiAnswer: Align with the magnetic field Better understanding of the nuclei is possibleAnswer: With the help of a mathematical translator called the fourier transfer algorithm All hydrogen atomsAnswer: Resonate at different frequencies depending on their environment. Why is it important to use a deuterated solvent?Answer: So the spectrometer can lock onto the sample to prevent the spectrum from drifting during aquisition Molar absorbtivities of compounds exhibiting charge transfer absorption areAnswer: Large Molar absorbtivity is the measure of theAnswer: Amount of light absorbed per unit concentration Which of the following relationships between absorbance and %transmittance is incorrect?Answer: A = log₁₀ 1 / T Why is it generally preferable to use absorbance as a measure of absorption rather than % transmittance?Answer: Because absorbance is proportional to the concentration of the analyte, whereas %T is not In the past, IR spectra had to be aquired one wavelength at a time, which took a long time. Today quick spectra is due to theAnswer: The Fourier Transfer Algorithm allows us to scan all frequencies at once Which of the following is not an IR vibrational mode?Answer: Rolling Which of the following will oscillate the fastest?Answer: A small mass on a stiff spring In the equation, A = ε bc, what quantity is represented by "ε"?Answer: Molar absorbtivity Why must the voltage supplied to a tungsten lamp be very stable?Answer: Because amount of energy the lamp emits is proportional to the fourth power of the operating voltage Where does a carbonyl (C=0) stretch appear in an IR spectrum?Answer: 1870-1650