Fluorescence Lifetime Measurements
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Questions and Answers

What is the primary function of appropriate filters in fluorescence microscopy?

  • To control the intensity of the emission light
  • To enhance the fluorescence intensity
  • To control the intensity of the excitation light
  • To select the excitation and emission wavelengths (correct)

    • Which of the following excitation light sources is commonly used in fluorescence microscopes?

  • Metal halide lamp
  • High power LED (correct)
  • Mercury vapor lamp
  • Xenon arc lamp

    • What type of semiconductor is formed by doping silicon with a trivalent element?

  • Intrinsic semiconductor
  • N-type semiconductor
  • Extrinsic semiconductor
  • P-type semiconductor (correct)

    • What occurs at a p-n junction in a semiconductor?

    <p>All of the above</p> Signup and view all the answers

    Which process releases energy relatively slowly in the form of light?

    <p>Phosphorescence</p> Signup and view all the answers

    What happens to fluorescence when the radiation source stops?

    <p>It ceases to glow immediately</p> Signup and view all the answers

    What is a fluorochrome?

    <p>A chemical that emits light</p> Signup and view all the answers

    Why does the emission spectrum have longer wavelengths than the excitation spectrum?

    <p>Due to the Stokes shift</p> Signup and view all the answers

    Which property of light is the most important in bioanalysis?

    <p>Wavelength</p> Signup and view all the answers

    What is the speed of light in a vacuum?

    <p>3 x 10^8 m/s</p> Signup and view all the answers

    What are the possible interactions when light is exposed to a material?

    <p>Transmission, absorption, absorption and re-emission, scattering, reflection, refraction, interference, and diffraction</p> Signup and view all the answers

    What does the absorption of light result in?

    <p>Transitions of a molecule from a ground state into an excited state</p> Signup and view all the answers

    Which of the following is true about forward bias in a p-n junction?

    <p>The p-type is connected to the positive terminal of the power supply</p> Signup and view all the answers

    Which of the following is true about reverse bias in a p-n junction?

    <p>The p-type is connected to the negative terminal of the power supply</p> Signup and view all the answers

    What happens when a photon of sufficient energy strikes a photodiode?

    <p>It creates an electron-hole pair</p> Signup and view all the answers

    What is the quantum yield of a molecule?

    <p>The ratio of emitted photons to absorbed photons</p> Signup and view all the answers

    Which of the following is a limitation of using stronger excitation light intensities in fluorescence lifetime measurements?

    <p>Stronger excitation light intensities can cause photo bleaching</p> Signup and view all the answers

    Which type of quenching occurs when the fluorophore is in the excited state and collisions with other species result in relaxation of the fluorophore without photon emission?

    <p>Dynamic quenching</p> Signup and view all the answers

    What is the efficiency of energy transfer in fluorescence resonance energy transfer (FRET) experiments?

    <p>The fraction of photon energy that is absorbed by the donor and transferred to the acceptor</p> Signup and view all the answers

    What is the Förster distance in the Förster equation for calculating the rate of energy transfer in FRET?

    <p>The distance at which the fluorescence energy transfer is 50% efficient</p> Signup and view all the answers

    According to the Beer-Lambert law, the linear relation between concentration and absorbance is described by the equation $A = \epsilon \cdot c \cdot l$, where $A$ is the absorbance, $\epsilon$ is the extinction coefficient, $c$ is the concentration, and $l$ is the path length. Which of the following statements is true about this equation?

    <p>The absorbance is directly proportional to the concentration and inversely proportional to the path length.</p> Signup and view all the answers

    Which of the following statements is true about the NanoDrop spectrophotometer?

    <p>It uses the surface tension of aqueous solutions to form a column of sample.</p> Signup and view all the answers

    What is the purpose of measuring the absorbance of the sample-free solvent ("blank") in spectrophotometry?

    <p>To account for losses due to reflection and scattering of light at the cuvette.</p> Signup and view all the answers

    What is the typical absorbance ratio A260/A280 for a pure DNA solution?

    <p>1.8</p> Signup and view all the answers

    Which of the following is a major application of fluorescence spectroscopy in biology?

    <p>Tracking tagged molecules in complex environments</p> Signup and view all the answers

    What is a limitation of conventional fluorescence microscopes?

    <p>They cannot image thick specimens</p> Signup and view all the answers

    Which of the following is a mutant of GFP that is fluorescent in a different wavelength region?

    <p>Yellow fluorescent protein (YFP)</p> Signup and view all the answers

    What can be observed using fluorescence microscopy?

    <p>Distinct parts of the cells</p> Signup and view all the answers

    What are the major applications of fluorescence spectroscopy in biology?

    <p>Tracking tagged molecules in complex environments</p> Signup and view all the answers

    What are the limitations of conventional fluorescence microscopes?

    <p>They cannot image thick specimens</p> Signup and view all the answers

    Which process releases energy relatively slowly in the form of light?

    <p>Phosphorescence</p> Signup and view all the answers

    What is a fluorochrome?

    <p>A label used in biological research</p> Signup and view all the answers

    Why is there an increase in wavelength?

    <p>Loss of vibrational energy</p> Signup and view all the answers

    What is the purpose of measuring the absorbance of the sample-free solvent ('blank') in spectrophotometry?

    <p>To eliminate background noise</p> Signup and view all the answers

    Which of the following is true about the operation of a photodiode?

    <p>A photodiode is operated with reverse bias.</p> Signup and view all the answers

    What is the purpose of the dynodes in a photomultiplier tube (PMT)?

    <p>To accelerate the electrons emitted from the cathode.</p> Signup and view all the answers

    What is the absorption maximum of fluorescein?

    <p>494 nm</p> Signup and view all the answers

    What is the quantum yield of fluorescein in 0.1 M NaOH?

    <p>0.93</p> Signup and view all the answers

    Which of the following excitation light sources is commonly used in fluorescence microscopes?

    <p>High power light-emitting diode (LED)</p> Signup and view all the answers

    What is the primary function of appropriate filters in fluorescence microscopy?

    <p>To select the excitation and emission wavelengths</p> Signup and view all the answers

    What occurs at a p-n junction in a semiconductor?

    <p>All of the above</p> Signup and view all the answers

    What is a diode?

    <p>A piece of semiconductor material with a p–n junction connected to two electrical terminals</p> Signup and view all the answers

    Which of the following interactions can occur when light is exposed to a material?

    <p>All of the above</p> Signup and view all the answers

    What is the speed of light in a vacuum?

    <p>3 x 10^8 m/s</p> Signup and view all the answers

    What property of light is the most important in bioanalysis?

    <p>Wavelength</p> Signup and view all the answers

    According to the Beer-Lambert law, the linear relation between concentration and absorbance is described by the equation $A = \epsilon \cdot c \cdot l$, where $A$ is the absorbance, $\epsilon$ is the extinction coefficient, $c$ is the concentration, and $l$ is the path length. Which of the following statements is true about this equation?

    <p>The absorbance is directly proportional to the concentration</p> Signup and view all the answers

    According to the Beer-Lambert law, the linear relation between concentration and absorbance is described by the equation $A = \epsilon \cdot c \cdot l$, where $A$ is the absorbance, $\epsilon$ is the extinction coefficient, $c$ is the concentration, and $l$ is the path length. Which of the following statements is true about this equation?

    <p>The absorbance is directly proportional to the concentration and path length.</p> Signup and view all the answers

    What is the typical absorbance ratio A260/A280 for a pure DNA solution?

    <p>1.8</p> Signup and view all the answers

    Which of the following is true about the NanoDrop spectrophotometer?

    <p>It measures DNA, RNA, and protein concentrations.</p> Signup and view all the answers

    What is the efficiency of energy transfer in fluorescence resonance energy transfer (FRET) experiments?

    <p>25%</p> Signup and view all the answers

    Which of the following is true about fluorescence lifetime measurements?

    <p>The detector used in fluorescence lifetime measurements must be able to measure in the nanosecond time range.</p> Signup and view all the answers

    What is the main limitation of using stronger excitation light intensities in fluorescence lifetime measurements?

    <p>Stronger excitation light intensities can cause photo bleaching.</p> Signup and view all the answers

    Which type of quenching occurs when a fluorophore is in the excited state and collisions with other species result in relaxation of the fluorophore without photon emission?

    <p>Dynamic quenching</p> Signup and view all the answers

    What is fluorescence resonance energy transfer (FRET)?

    <p>The transfer of energy from a fluorophore in the excited state to a fluorescent or non-fluorescent acceptor molecule.</p> Signup and view all the answers

    Which of the following is a major application of fluorescence spectroscopy in biology?

    <p>Observing protein movements in specific parts of the cell or organism</p> Signup and view all the answers

    What is the primary function of appropriate filters in fluorescence microscopy?

    <p>To selectively transmit excitation light and block unwanted emission light</p> Signup and view all the answers

    What is a limitation of conventional fluorescence microscopes?

    <p>They are not suitable for imaging thick specimens like tissue samples</p> Signup and view all the answers

    What are the possible interactions when light is exposed to a material?

    <p>Absorption, reflection, transmission, and scattering</p> Signup and view all the answers

    What is the efficiency of energy transfer in fluorescence resonance energy transfer (FRET) experiments?

    <p>Depends on the distance between the donor and acceptor fluorophores</p> Signup and view all the answers

    Which of the following is a mutant of GFP that is fluorescent in a different wavelength region?

    <p>Yellow fluorescent protein (YFP)</p> Signup and view all the answers

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