BCMB 311‚ Advanced Cell Biology‚ Fall 2012 EXAM 1 __________________________________Name True-False Questions (Write T or F next to the question‚ 1 point each) 1. A globular protein in the cytoplasm will normally be folded up in such a way that most of its non-polar sidechains are buried in the interior of the protein and most of its polar and charged side-chains are exposed on its surface. T 2. Alpha helices are stabilized by hydrogen bonds between amino acid side chains‚ whereas beta
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Do Electrons Really Exist? Science has defined the nature of the world through an assortment of things that are observed in the physical world and those that are unobservable‚ improvable theories that explain the world. Electrons are unobservable. We cannot experience their existence with our own human senses. Do electrons really exist‚ or are they just useful fictions? Antirealists would explain that they do not exist because you cannot observe them. Realists would argue that electrons
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inversely proportional to the percent transmission for the yellow light which implied more photoelectrons were emitted for greater intensity. Stopping potentials for green light was noted to be higher than of yellow light. Ratio of Planck’s constant to electron charge and work function of the photocathode were determined experimentally from the plot of frequency vs. stopping potential from the first and second orders of spectral lines of mercury. The h/e ratio from the plot was 2.345 × 10-15 eV•s with 43
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(substance that cannot be broken down into further substances) Atom (smallest unit of an element) – subatomic particles (neutrons‚ protons‚ electrons) Compound (2 or more) Atomic number - # of protons Atomic mass = # of neutrons and protons Ion – total number of electrons doesn’t equal # of protons (anion gained electrons‚ cation lost electrons) Electron shells‚ orbitals‚ valency‚ rule of 8 Bonds = ionic‚ covalent (polar‚ nonpolar)‚ hydrogen‚ Van der walls Electronegativity Relationship of
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crystalline surfaces including both atomic structures and electron arrangement. The STM tip produced in this experiment acts as a needle that hovers above the crystalline material surfaces (perfect atomic structural patterns) with nanoscale accuracy‚ while emitting electrons from a few nanometers above the surface of the crystalline materials‚ utilizing the quantum tunneling effect to scan the surface atoms and electrons. In classical physics; electrons would not be able to pass through certain conductive
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water takes to reach its destination. This can be applied in the variables of resistance. The electrons ’bounce ’ off the atoms - this causes the electrons to head elsewhere rather than the desired direction. In a long tube there are more atoms‚ this slows the electrons down as they ’bounce ’ off into another direction. In a short tube‚ there are less atoms which means there are less to deflect the electron any more speeding the speed up. In theory‚ the length should be proportional to the resistance
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The History of the Atom Hypothesis according to Aristotle (350 BC): All matter consists of the elements earth‚ air‚ fire‚ and water. Experiment: A tree grows from the earth as water is added. The tree is then set on fire in an effort to form new elements. 1. What kind of results would be observed from this experiment? Fire‚ ash (earth)‚ smoke (air) 2. Would these observations support or reject the hypothesis? Explain. Support. No elements have been produced that are something other than
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Photoelectric effect Shining light on a metal causes electrons to be emitted Below some frequency‚ no photons are emitted regardless of intensity of light. As frequency of the light increases‚ the kinetic energy of the emitted electrons increase. As the intensity of the light increases under a certain frequency‚ the number of the electrons ( current I) increases. Photon energy is quantized. Some energy is needed to liberate an electron form a material. This amount of energy is called the
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1. How is electricity produced? The most simple way of producing static ekectricity is by rubbing or friction. When you rub two different kind of materials that are insulator‚ you can transfer electrons from one substance to another. Nowadays‚ to create electricity we use battery and generators. Voltage can be made by heart‚ light or mechanical pressure. http://science.howstuffworks.com/electricity-info2.htm 2. Where and how is electricity used? Electricity gives us ability to produce
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XRD – X-Ray Diffraction X-ray diffraction (XRD) is a powerful non-destructive technique for characterizing crystalline materials. It provides information on structures‚ phases‚ preferred crystal orientations (texture)‚ and other structural parameters‚ such as average grain size‚ crystallinity‚ strain‚ and crystal defects. X-ray diffraction peaks are produced by constructive interference of a monochromatic beam of X-rays scattered at specific angles from each set of lattice planes in a sample. The
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