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Minimals 1 - Lecture 1-10

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Biophysics (1st year/ 1st semester) Flashcards on Minimals 1 - Lecture 1-10, created by Hannah Stadelmann on 10/07/2017.
Hannah Stadelmann
Flashcards by Hannah Stadelmann, updated more than 1 year ago
Hannah Stadelmann
Created by Hannah Stadelmann almost 5 years ago
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Question Answer
1. Define kinetic energy in words and with a formula, and give its unit!
2. Define electron volt (eV)!
3. Define what force is!
4. Define acceleration in words and with a formula!
5. Define Newton’s 2nd law in words and with a formula!
6. Define centripetal acceleration in words and with a formula!
7. Define angular velocity in words and with a formula!
8. Define momentum in words and with a formula!
9. Define moment of inertia in words and with a formula!
10. Define angular momentum!
11. Define the potential energy of an object in a homogenous gravitational field!
12. Define the potential energy of a charged object in an electrostatic field!
13. Define work in words and with a formula!
14. Formulate the general form of the work-energy theorem, and its special form for the electric and homogenous gravitational fields! 1 General form, m is the mass, vB and vA are the speed of the object at point A and B, respectively, WAB is the work done on the object between points A and B.
14. Formulate the general form of the work-energy theorem, and its special form for the electric and homogenous gravitational fields! 2 In an electric field, Q is the charge of the object, UAB is electric potential difference between points A and B
14. Formulate the general form of the work-energy theorem, and its special form for the electric and homogenous gravitational fields! 3 In a homogenous gravitational field, hAB is the height difference between points A and B.
15. Define power in words and with a formula, and give its unit!
16. Define the term and unit of voltage!
17. Define electric current and derive its unit from other SI units!
18. Define resistance and give its unit!
19. Define what electric dipole is, and describe how to calculate its electric dipole moment!
20. Give the energy and momentum of a photon with frequency f.
21. What is the difference between the orbital and spin angular momenta of an electron?
22. Align in ascending order the following components of the electromagnetic spectrum according to their energy: microwaves, gamma, ultraviolet, visible light, X-ray, infrared, radiowaves!
23. What is the definition of visible light?
24. What is the wavelength range of ultraviolet radiation? 10nm – 400nm
25. What is the wavelength range of infrared radiation? 750nm – 1mm
26. Define the limiting frequency (fmax) of braking radiation at an accelerating voltage of U.
27. What is the major difference between the photoeffect and the Compton effect?
28. What is the minimal energy of a γ-photon needed for pair-production (not numerically)?
29. Why is a heavy nucleus necessary for pairproduction? The presence of a heavy nucleus is required by the law of conservation of momentum.
30. What is annihilation?
31. List the three most important mechanisms responsible for the absorption of γ and X-rays! - photoelectric effect - Compton-effect - pair-production
32. Define interference! Interference is the superposition of waves that results in the generation of a new wave pattern.
33. What is constructive and destructive interference?
34. What is the requirement for maximally constructive and maximally destructive interference if two propagating waves with identical wavelength interfere with each other?
35. Give the condition for constructive interference for an electromagnetic wave with wavelength λ diffracted on a crystal with a grating constant of c! (angle of incidence is 90°)
36. How can the overdetermination of the Laue equations be resolved in the case of a three dimensional crystal? Either by rotating the crystal or making powder of it.
37. What is the definition of transverse and longitudinal waves?
38. What is monochromatic light? Light is monochromatic if its spectrum consists of a single wavelength only
39. What kind of special characteristics does laser light have? - monochromatic - coherence in time and distance - small divergence - high light density
40. List the types of interactions laser light can have with tissues!
41. When is electromagnetic radiation coherent? If it consists of photons capable of forming observable interference fringes.
42. What basic phenomena is the generation of laser emission based on?
43. What is the approximate coherence length of a laser and that of a classical light source?
44. Align in ascending order the following transition according to their energy difference: vibrational, rotational and electronic! rotational < vibrational < electronic
45. Write the Lambert-Beer law and interpret the variables in the formula!
46. What does the molar extinction coefficient depend on?
47. How many fold does the intensity of light decreases if the absorbance (optical density, extinction) of a solution is 1? It decreases 10-fold.
48. What is the definition of the molar extinction coefficient? It is the absorbance (optical density) of a solution with a concentration of 1M and an optical path length of 1 cm.
49. At what wavelength are the characteristic absorption maxima of proteins and nucleic acids? proteins 280 nm, nucleic acids 260 nm
50. Which amino acids have reasonably high absorption? Tyr, Trp, Phe
51. What is the definition of a singlet and a triplet state?
52. What are the possible ways of relaxation of an excited electron in a molecule? (List at least 5 of them!)
53. What is the definition of fluorescence lifetime? The time during which the number of excited molecules decreases to 1/e-times (37 %) of its initial value.
54. What is a., scintillation, b., chemiluminescence, c., photoluminescence? Processes where photon emission is elicited by a., ionizing radiation b., chemical reaction c., excitation by photons.
55. How can fluorescence quantum efficiency (yield) be defined? (One definition is sufficient.) The fraction of excited molecules emitting a fluorescent photon, OR the number of fluorescence photons divided by the number of absorbed photons, OR the rate constant of fluorescence divided by the rate constants of all possible de-excitation processes.
56. Why is the fluorescence quantum yield always smaller than one? Because relaxation from the excited state can be accomplished not only by fluorescence emission.
57. What is the lifetime range of fluorescence?
58. What is the lifetime range of phosphorescence?
59. Why is phosphorescence lifetime longer than fluorescence lifetime? Because phosphorescence is the result of spin-forbidden transitions.
60. What are the requirements of Förster-type resonance energy transfer?
61. Why is Förster type resonance energy transfer a sensitive method for distance measurements? Because its probability is proportional to the inverse sixth power of the separation between the donor and the acceptor.
62. What can Förster-type resonance energy transfer be used for in biology? For measuring inter- and intramolecular distances.
63. What is photoselection? It is the selection of an oriented subpopulation from a randomly oriented population of molecules by linearly polarized light.
64. What is linearly polarized light? Light in which the electric vectors of all photons point in the same direction.
65. List at least five parameters which can be determined using fluorescent measurements!
66. Define the index of refraction!
67. Write Snell’s law of refraction!
68. What is the shortest resolvable distance in a light microscope? approximately 200 nm
69. How can the resolving power of a microscope be increased?
70. What is numerical aperture?
71. Give the formula for the resolving power of a conventional light microscope!
72. What is the function of the dichroic mirror in a fluorescence microscope? It reflects the excitation light, and is transparent for the emitted photons, therefore it separates the excitation and emission light paths.
73. What is the function of the excitation filter in a fluorescence microscope? It is transparent only in the wavelength range in which the fluorescent dye can be excited, therefore it allows only those photons to reach the sample which can excite the fluorescent molecule.
74. What is the function of the emission filter in a fluorescence microscope? It is transparent only in the wavelength range in which the fluorescent dye emits photons, therefore only the photons emitted by the fluorescent dye will reach the detector.
75. List the imaging aberrations in optical systems!
76. Give the equation for the relationship between the image distance (i), object distance (o) and the focal distance (f)!
77. Give the definition and SI unit of diopter!
78. What were those two discoveries that made construction of an electron microscope possible?
79. List at least three signals that can be detected during an electron microscopic measurement!
80. What are the two types of electron microscopes? transmission electron microscope (TEM) scanning electron microscope (SEM)
81. What is the principle of transmission electron microscopy?
82. What is the principle of scanning electron microscopy? The sample is scanned by a thin electron beam. Secondary electrons induced by the electron beam are detected on a pixel-by-pixel basis.
83. Give the definition of isotopes! Isotopes are the variants of a chemical element with a given atomic number whose mass numbers are different.
84. List the isotopes of hydrogen with their mass number and the constituents of their nuclei!
85. What is the mass defect of nuclei?
86. What is the relationship between the total binding energy (ΔE) and the mass defect (Δm) of a given nucleus?
87. Describe how the binding energy per nucleon changes as a function of mass number. Binding energy per nucleon has a maximum at nuclei with mass numbers 55-60 (i.e. Fe).
88. What are the properties of nuclear force (their range, strength and direction)?
89. On what kind of energy level does a nucleon reside in a nucleus compared to the energy of a free particle? A bound nucleon has negative potential energy compared to a free particle.
90. List the types of radioactive radiation and characterize the particles constituting them!
91. What is the direction of changes in the atomic number and the mass number of nuclei during alpha, both types of β and gamma decay?
92. Why is the spectrum of beta decay continuous? Besides an electron (or a positron) an antineutrino (or a neutrino) is also emitted, and the energy released during the decay is shared randomly between the two particles.
93. What is electron capture and what does it produce?
94. Give the equation describing the number of undecayed nuclei as a function of time (i.e. the law of radioactive decay) .
95. What is the physical meaning of the radioactive decay constant? Radioactive decay constant is equal to the inverse first power of the mean lifetime of a radioactive nucleus.
96. What is the relationship between the radioactive decay constant (λ) and the half life (T)?
97. Define biological half life. Biological half life is the time period during which half of the initial quantity of the radioactive isotope leaves the living system undecayed due to metabolism, secretion or excretion.
98. Define effective half life.
99. Describe the relationship between the effective (Teff), the physical (Tphys) and the biological (Tbiol) half lives!
100. Describe the relationship between the physical (λphys), the biological (λbiol) and the effective (λeff) decay constants!
101. Write the formula describing the attenuation of gamma or X-ray radiation in an absorbing material.
102. What is the definition of the attenuation coefficient of a material for gamma or X-ray and what is its SI unit?
103. How does the intensity of -radiation change as a function of the distance from the radiation source? It is constant in the beginning then suddenly decreases to zero.
104. What is responsible for the energy loss of an alpha particle along its path? Ionization.
105. What kind of radioactive radiations can be detected by a GM-counter? α-, β- and γ-particles can be detected.
106. What is the basic principle of operation of a photomultiplier tube?
107. What is the basic operation principle of ionization detectors?
108. What is the principle of detection of radioactive radiation by a scintillation detector? In certain organic and inorganic substances the energy of radioactive particles is converted to luminous energy, i.e. they generate visible light flashes.
109. List the radioactive radiations in order of increasing penetrability! α<β<γ
110. What is the biological effect of radioactive radiation based on? Excitation and ionization of atoms and/or molecules of living systems.
111. What kind of particles are able to produce a biological effect in radiation biology? Particles giving their energy partially or totally to the biological object are able to produce a biological effect.
112. What is a hit in radiation biology? If one or more ionizations are produced in the radiosensitive volume of a biological object.
113. How can a dose-response curve be constructed? The applied radiation dose is plotted on the horizontal axis and the ratio of the surviving organisms (N) and the total number of organisms before irradiation (N0) is plotted on the vertical axis.
114. What is the probability of generating exactly ‘n’ hits when applying a dose of D in volume V?
115. How does the number of ionizations depend on the dose of the radiation? The number of ionizations is linearly proportional to the dose.
116. Write the equation describing the dose-response curve when one hit is necessary for inactivation?
117. What is D37? D37 denotes the dose at which 37 % of the irradiated objects survive. If one ionization causes inactivation, D37 corresponds to one hit in a radiosensitive volume (VD=1, that is D=1/V).
118. What is the principle of the indirect action of radiation?
119. What kind of products are capable of damaging biological objects arise during irradiation of aqueous solutions?
120. What is the definition of absorbed dose?
121. What is the definition and unit of KERMA (kinetic energy released in material)?
122. What is the definition and unit of exposure in the case of X-ray and γ-radiation?
123. Define the unit of equivalent dose!
124. List the physical factors influencing radiation sensitivity!
125. What is the smallest dose which can produce a biological effect? Theoretically even a single quantum is enough to produce a point mutation, since any photon that is able to produce ionization is capable of breaking a chemical bond.
126. How can radioactive radiation cause a double strand break in DNA?
127. Write the equation describing cell survival according to the linear-quadratic model. Where S(D) is the survival fraction as a function of dose D, and α and β are tissue and radiation dependent constants. Parameters α and β are proportional to the probability of "one-step" and “two-step” DNA double strand breaks, respectively.
128. In which part of the cell cycle are cells the most and the least sensitive to radioactive radiation? Generally, the majority of cells are considered to be the most radiosensitive during mitosis and most resistant in late S phase.
129. How does radiosensitivity changes as a function of the level of oxygenation? The well-oxygenated cells have greater radiosensitivity than hypoxic cells, because in the presence of oxygen there is higher chance to produce radicals.
130. How and why does fractionation of radioactive radiation influence the radiosensitivity of cells? Fractionation decreases the radiosensitivity of cells, because radiation-induced damage can be partly repaired between exposures to the radiation.
180. Give the frequency range of sound waves audible by a normal human ear! 20 Hz - 20000 Hz.
181. What is ultrasound?
182. What is infrasound? Sound with a frequency less than 20 Hz.
183. Give the definition and unit of sound intensity!
184. What does the velocity of sound depend on? The velocity of sound depends on the properties of the medium (density and compressibility).
185. What does acoustic impedance depend on?
186. List the most widespread effects suitable for the generation of ultrasound!
187. Describe the relationship between the amplitude of the ultrasound-induced pressure fluctuation (ΔPmax) and the intensity of ultrasound (J)!
188. What is cavitation?
189. How does the intensity of ultrasound change while it passes through a certain medium?
190. What is the basis of imaging with ultrasound?
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