BCH Practice Questions – Flashcards
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What is the length of a typical C-H chemical bond, in Angstroms, and meters? What is the diameter of a typical bacterial cell? What are the wavelengths of red & blue light? UV light? X-rays? Infrared light?
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approximately 1 angstrom = 10^-10 meters Bacterial cell = 1 micron Wavelength of visible light 400-700. Red = 700 nm, blue = 450 nm UV = 350 nm, X ray = 0.1 to 100 angstroms. Infrared = microns
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The wavelength of red light is approximately ________________ times greater than the length of a C-H covalent bond. (circle one best answer)
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CH bond is 1 angstrom = 0.1 nm red light ~ 700 nm 7000 times greater
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Which of the following statements are true? Be able to explain why each statement is true or false. a) Prokaryotes are made up of two major groupings: the bacteria and the archaea. b) If a species consists of only a single cell, it must be a prokaryote. c) If a cell contains chloroplasts or mitochondria, it must be from a eukaryote. d) All prokaryotes are bacteria.
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a) true b) false - protists, cyanobacteria c) true - organelles d) false, some can be archaea
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Light with a wavelength of 280 nm can be best described as
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UV
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Analysis of radioactive decay products indicates that the oldest rocks on earth were formed approximately ________________________________ years ago.
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4.5 billion years ago
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Imagine that you found an unusual species of prokaryote growing in a high- temperature environment. What is the best way to determine whether this prokaryote is a bacteria, or archaea?
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Sequence it's genome and look for conserved sequences - is it more similar to bacteria or archaea
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What is the approximate length of a C-C single bond, in cm, nm, and in microns?
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1.5 angstrom = .15 nm = 1.5 E-4 microns = 10^-8cm It would be 10^-7 millimeters
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Estimate the number of OH- ions in a single bacterium at pH 7. I don't expect an exact answer, just get it correct to within an order of magnitude. You should be able to make a reasonable (order of magnitude) estimate without consulting a reference source.
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KW = 10^-14. At pH 7 that means there are 10^-7 OH ions. A single bacterial is about 1um ^3 (assume it's a box). That means that there are um^3 volume of water which = 1ug of water = X amount of moles = X *6.02E23 amount of mc and half of them should be OH ions. Volume of E. coli is about 1 micron3 = 10^-18 m3 = 10^-15 liters (very approximate) concentration of OH at pH 7 is 10^-7 moles/liter E. coli contain (10^-7 moles/liter OH) x (10^-15 liters) = 1 x 10^-22 moles of OH multiply by Avagadro's number to get about 60 OH ions (approx.)
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Which one of the following molecules has the highest boiling point? Which has the 2nd highest boiling point? The lowest boiling point? Explain your choices. A) H2O B) CH4 C) O2 D) NH3 E) N2 F) H2
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H2O has the highest boiling point. Then NH3, then CH4, then O2, N2, then H2. Rank first by molecular interactions, then by molecular weight. H2O has the most hydrogen bonds. H2 is the lightest compount
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Which two of the following species are most likely to contain a cell nucleus? A) Escherichia coli. B) Saccharomyces cerevisiae (yeast) C) A species of archaea. D) A species that is prokaryote. E) Drosophila melanogaster (fruit fly)
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B) Saccharomyces cerevisiae (yeast) E) Drosophila melanogaster (fruit fly)
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Consider the reaction: glucose + 6 O2 ==> 6 CO2 + 6 H2O Which molecule is being reduced as this reaction proceeds to the right?
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glucose is being oxidized. Oxygen is being reduced.
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Look up the structure of the amino acid glutamate. The charge of a molecule of glutamate at pH 7 is closest to ______ and at pH 12 it's closer to ___________
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Glutamate is acidic. so it's closest to -1 at pH 7 but at pH 12 it's probably closer a charge to -2 because the NH2 is no longer protonated
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A sample of pure water is heated to a temperature of 112 C at a pressure of 20 MPa, where the ionization constant for water is 4.0 x 10-12. What is the OH- concentration in the pure water at these conditions?
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Kw = 4.0 x 10-12 = [H3O+] [OH¯]. If it's pure water...then it's half and half so OH- concentration = 2 x 10-6
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Assume that 100 mM HCl is added to a sample of pure water at the conditions (pressure of 20 MPa and a temperature of 112 C) described in part (a). What is the approximate pH of the solution?
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pH = 1.0 = - log [H+ concentration] in moles/liter 100 millimolar = .1 molar (moles/liter) pH = 1.0 = -log [.1] Note that the concentration of H+ ions in water is 2x10^-6 moles... so .1 + 2x10^-6 is effectively 0.1 so we can just use that to estimate the pH of the solution
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Approximately how many years ago did the first prokaryotic life appear on earth?
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3.8 billon years ago
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Approximately how many years ago did the most recent common ancestor of C. elegans (a worm, and invertebrate) and humans live?
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first vertebrate appeared about 525 x 10^6 years ago (approximate) So 525 million years ago
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What is the approximate volume of an E. coli cell, in cubic meters, and in liters? Try making your best guess, and then see if you can find an opinion on the web. Hopefully you agree to within a factor of 10 or so. (b) How many water molecules does an E. coli contain?
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E. Coli is approximately um3 in volume. we know there are 10^-6 meters in a um. then that means 10^-18 m^3. If we assume that E.coli is HALF water (remember humans are about 60% water). that means that we have 10^-15 liters. 3E11 water mc
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A healthy human neuron is in a state of chemical equilibrium. True or false?
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FALSE or else we would be deaded
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Look up the structure of the amino acid tyrosine. A tyrosine amino acid has a side chain with a pKa of about 10.5. Draw the chemical structure of the major form of tyrosine at pH 9.5, with appropriate charges shown.
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Tyrosine should have amino group without an additional H, COO- and OH should be protonated
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Light with a wavelength of 320 nm is best described as
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UV
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Which of the following molecules has the greatest dipole moment, when dissolved in water at pH 7 A) carbon dioxide B) carbon monoxide C) glycine D) oxygen (O2)
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Carbon Monoxide
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The structure of tyrosine is shown below, as it appears on Wikipedia. Assume the pKa's of the three titratable groups are 2.5, 9.1 and 10.1. The phenolic -OH group has a pKa of 10.1. a)Draw the chemical structure of the major form of tyrosine in aqueous solution at pH 1.5, and at pH 12. Indicate charges appropriate for each pH. (b) Approximately what percentage of the tyrosine carboxylate groups are deprotonated at pH 3.6?
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at pH 1.5, everything should be protonated. NH3+, COOH, and OH at pH 12 everything should be deprotonated. NH2, COO-, O- We know that carboxylate group of tyrosine has a pka of 2.5 (exactly 50/50 protonated and deprotonated) then at pH 3.6, you'll have LESS protonated - related by the Henderson Hasselbalch equation pH = pka + log [base]/[acid].
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pKAs occur at 2.34, 9.6. When dissolved in water, this molecule would be an effective buffer near what value(s) of pH?
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It's pKAs, 2.34, 9.6.
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Which reaction is most likely to occur spontaneously? A) there is large decrease in enthalpy and increase in entropy as products form. B) there is a large increase in enthalpy and decrease in entropy as products form. C) there is a large increase in free energy as reactants are converted to products. D) all of these are likely to be spontaneous. E) none of these likely to be spontaneous. Write the letter corresponding to the one best choice here: ________________
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A
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Consider the ATP hydrolysis reaction: ATP + H2O ADP + Pi (a) What it is the free energy of ATP hydrolysis at conditions of pH 7, in water solvent, with 1 mM magnesium, T = 37 C, [ATP] = 4 mM, [ADP] = 0.4 mM, [Pi ] = 7 mM.
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Use dG = g' + RTln [Prod]/[React]
