33. You bathe neurons in a salt solution that has Na+ and K+ radioactively label

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33. You bathe neurons in a salt solution that has Na+ and K+ radioactively labeled. You immediately stimulate the cells to fire an action potential, then you wash off the media and test the cells for radioactivity. What do you expect to find in the cells? a. no labeled Na+ or K+ b. mostly labeled Na+ c. mostly labeled K+ d. equal amounts of labeled Na+ or K+ 84. Cells store energy via creating electrochemical gradients. Consider the equation o Ci/Co + zFAEm and the fact that the concentration difference between outside and ytosol for Ca++ is 10,000 fold, for Nat is about 10-20 fold, and for Mg++ is about 2-4 inside thec fold. Which ion concentration different stores the most energy? a. b. Ca++ c. d. Na+ they are all equal Tired of the recent Stinkbug infestation, you develop a new pesticide that targets an enzyme required for Stinkbug survival. This enzyme also happens to have a homolog in humans. The new drug makes a complex with the target to inihibit its function. The dissociation of this complex, C, into the drug, D, and its target, E, individually, can be described by the dissociation constant, Kd. Which of the following Kds would be most desirable in continuing to pursue marketing this drug? a. 1 nM b. 10 nM c. 1 mM 35. d. IuM e. 10mM 36. Which of the following is NOT a tenet of the Cell Theory? All organisms are composed of one or d. Viruses require cells to grow a. more cells Cells only arise from division from a pre-existing cell The cell is the structural usnit of life All of the above are part of the Cell Theory b. e. c. Matching Experimental methods-Match the description to the method (at least one answer will be used twice) a. scanning electron microscopy b. laser scanning confocal microscopy e. X-ray crystallography c. SDS-PAGE d. FRAP 37. separates denatured proteins by mass 38. type of microscopy that can resolve objects 10 nanometers apart 39. type of microscopy that illuminates a specimen with ultraviolet light, then collects emitted light of a different wavelength from one focal plane through an aperture 40. method to resolve objects a few Angstroms apart 41. method that provided early evidence for the fluidity of the "fluid mosaic" model of membranes 42. provides information about tertiary structure of proteins

Explanation / Answer

33. c. mostly labelled Na+

During action potential, there is depolarization and repolarization. During depolarization, more Na+ ions will be pumped into the inner side the cell which are moved out during repolarization. The action potential lasts only 1 milli second. So finally, more sodium oons will be outside the cell and more pottassium ions will be inside the cell.

34. c. Ca++

According to the equation given, log10Ci/Co is different for each ion

For Ca++, it is log10 10,000 = 4

For Na+,, it is log10 10 or 20 = 1 or 1.3

and for Mg++, it is log10 2 or 4 = 0.3 or 0.6

electrostatic gradient (moving a negative charge against a voltage of 70 mV

Thus the deltaG is highest for Ca ions.

35. a. 1nM

The smaller the dissociation constant, the more tightly bound the drug to the target. Dissociation constant is the concentration of the ligand (drug) at which half of the protein (target) is occupied at equilibrium.

36. d. viruses require cells to grow

All the other options are part of cell theory

37. c - SDS-PAGE

this electrophoretic method helps to separate proteins according to their mass with the help of the chemical SDS, which provide negative charge to protein.

38. a. scanning electron microscopy

Of two 2 types of electron microscopes, scanning tunneling microscope has a resolution power of 10nm. Transmission of modern transmission electron microscope is 0.2nm.

39. ---- The type of microscopy that illuminates obect with UV is UV microscopy. But laser as source is used in laser scanning confocal microscopy

40. e. X-ray crystallography

41. d. FRAP - fluorescence recovery after photobleaching

This technique helps in the studies of cell membrane, diffusion through fluorescently labelled membranes and the protein binding with the membrane. Characterization of hydrophic and hydrophobic surfaces of fluorescent labelled phospholipid layer is possible by this technique in terms of surface structure and free energy.

42. e. X-ray crystallography provides information about secondary and tertiary structure of proteins like hemoglobin, myoglobin, bovine pancreatic ribonuclease and insulin. On striking a specifically oriented crystal of a protein, X-rays get scattered by the electons of its atoms. These X-rays produce an X-ray diffraction pattern on a photographic film.

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