1. Bacteria have a membrane potential, although the mechanisms of how it is maintained differfrom those of mammalian cells. The transport of protons across the cell membrane is animportant part of the mechanism, so a bacterium's membrane potential varies with the protonconcentration the pH of the surrounding fluid. One strain of bacteria was found to have amembrane potential of -120 mV at a pH of 7.5. A bacterium can be modeled as a 1.5-µm-diameter sphere. How many positive ions are needed on the exterior surface to establish thismembrane potential? (There are an equal number of negative ions on the interior surface.)Assume that the membrane properties are the same as those of mammalian cells.

Answered: Image /qna-images/answer/7af061ce-c70f-44f5-914d-e464f59ffd4a.jpg

Answered: Bacteria have a membrane potential,…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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What could happen to the proteins of cells treated with high amounts of free radicals that would effect the diffusion of those treated cells?
Do question 4 d) d) Calculate the fraction of histidine (amino acid shown below), that has its imidazole side chain protonated at pH 6.4. The pK, value for the imidazole group of histidine is 6.
In the absence of tension, MscL channel has an energy gap separating the closed and open states Eo = 50 kT. MscL opening is associated with a 20 nm2 in-plane protein expansion (change in A). Plot its open probability (Po) as a function of membrane tension. What will be the open probabilities of two MscL channels if one situates at the pole of the bacterial cell above, another in the middle?
In the early days of ribosome research, before the exact role of ribosomes was clear, a researcher made the following observation. She could find, in sedimentation experiments on bacterial lysates, not only 3OS, 50S, and 70S particles, but also some particles that sedimented at about 100S and 130S. When she treated such a mixture with EDTA, everything dissociated to 30S and 50S particles. Upon adding divalent ions, she could regain 70S particles, but never 100S or 130S particles. (a) Suggest what the 10oS and 130S particles might represent, in light of cur- rent knowledge of protein synthesis. What important discovery did the researcher miss? (b) Why do you think reassociation to 100S and 130S particles did not work?
A transmembrane protein helps catalyze the transport of solute A from the INSIDE TO the OUTSIDE of a cell. The reaction can be represented by the reaction coordinate diagram below. It is possible to conclude that the concentration of A on the outside of the cell is than its concentration on the inside AND that it is_ to expect that the protein will at some point form a continuous path between th cytosol and the extracellular environment. A inside A outside reaction coordinate O lower; reasonable O higher; unreasonable O higher; reasonable free energy
In the experimental conditions described below, how many molecules of dextrose do you have to add to the extracellular fluid in order to make it iso-osmotic relative to the intracellular fluid? Intracellular fluid: Number of water molecules = 60 • Number of Dextrose molecules = 7 • Number of Sucrose molecules = 3 ● Extracellular fluid: • Number of water molecules = 160 • Number of dextrose molecule = ???? • Number of Sucrose molecules = 0
List two differences you would expect to see in the composition of lipids in the E. coli membrane when the cells are incubated at 25 °C compared to incubation at 37 °C.
Why is there a difference in the way these two kinds of cells react in a hypotonic solution?
If protein X produces a higher absorbance reading at pH 7 than it does at pH 9, what can you conclude? Question 1 options: A lesser amount of protein X was used in the reaction at pH 7 than at pH 9. A greater amount of protein X was used in the reaction at pH 9 than at pH 7. Protein X is a more efficient catalyst at pH 7 than it is at pH 9. Protein X is a more efficient catalyst at pH 9 than it is at pH 7.

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