In order to investigate the action of a bacterial membrane protein that is a light-driven proton pump, you purify the protein and assemble it together with phospholipids into liposomes that contain an indicator dye, which is blue at high pH, colorless at neutral pH, and red at low pH. You then expose the liposomes, in an aqueous solution, to sunlight. The interior of the liposomes turn blue. Further investigatin of the proton pump protein you find that treatment of either intact bacteria or the purified protein with the protease chymotrypsin result in cleavage of the protein at a single site near the amino terminus, which destroys its capacity to pump protons. When you treat the liposomes described above with chymotrypsin, the interior of the liposomes remains colorless. From these results create a diagram of that illustrates the orientation of the pump protein in the plasma membrane of the intact bacterium and the direction in which it pumps protons. Explain your reasoning

In order to investigate the action of a bacterial membrane protein that is a light-driven proton pump, you purify the protein and assemble it together with phospholipids into liposomes that contain an indicator dye, which is blue at high pH, colorless at neutral pH, and red at low pH. You then expose the liposomes, in an aqueous solution, to sunlight. The interior of the liposomes turn blue. Further investigatin of the proton pump protein you find that treatment of either intact bacteria or the purified protein with the protease chymotrypsin result in cleavage of the protein at a single site near the amino terminus, which destroys its capacity to pump protons. When you treat the liposomes described above with chymotrypsin, the interior of the liposomes remains colorless. From these results create a diagram of that illustrates the orientation of the pump protein in the plasma membrane of the intact bacterium and the direction in which it pumps protons. Explain your reasoning

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter2: Cell Physiology

Section: Chapter Questions

Problem 11RE

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In order to investigate the action of a bacterial membrane protein that is a light-driven proton pump, you purify the protein and assemble it together with phospholipids into liposomes that contain an indicator dye, which is blue at high pH, colorless at neutral pH, and red at low pH. You then expose the liposomes, in an aqueous solution, to sunlight. The interior of the liposomes turn blue. Further investigatin of the proton pump protein you find that treatment of either intact bacteria or the purified protein with the protease chymotrypsin result in cleavage of the protein at a single site near the amino terminus, which destroys its capacity to pump protons. When you treat the liposomes described above with chymotrypsin, the interior of the liposomes remains colorless. Create an illustration/ diagram of that illustrates the orientation of the pump protein in the plasma membrane of the intact bacterium and the direction in which it pumps protons.
If you start with 100 mM Na+ and 100 mM K+ outside the liposomes, and 100 mM Na+ and 100 mM K+ inside the liposomes like in (A), then you add ATP to the solution outside the liposomes, then how will the Na+ and K+ concentrations change?
Draw and label a cell lipid bilayer and diagram how the following transport processes take place: passive diffusion of oxygen into the cell, facilitated diffusion of potassium into the cell, active transport of sucrose into the cell. Using different symbols (circles for oxygen, squares for sucrose, and triangles for potassium ions), show the relative concentrations (gradients) of these substances on the inside and outside of the cell. For example, to show that oxygen enters the cell by going “down” its gradient, you would draw more circles on the outside of the cell than inside the cell. Be sure to show and label membrane proteins when appropriate, and show the electric membrane potential using “+”s (pluses) on one side and “-”s (minuses) on the other side of the membrane. Also show the proton pump which uses ATP as a source of energy.
Proteins may be bound to the exoplasmic or cytosolic face of the plasma membrane by way of covalently attached lipids. What are the three types of lipid anchors responsible for tethering proteins to the plasma-membrane bilayer? Which type is used by cell-surface proteins that face the external medium? By glycosylated proteoglycans?
While performing fluorescent microscopy to observe the transport of bulk molecules into a cell a researcher uses a green, fluorescent bulk protein and a red fluorescent dye to stain the cell membrane. If the cell has the ability to transport the bulk proteins into the cell, what would we expect to see in the microscope when the images are merged? What would we expect to see if the cell did not have the ability to transport the bulk protein?
Acidification is achieved by an H+ pump in the endosomal membrane, which also contains Cl– channels. if the channels do not function properly (e.g., because of a mutation in the genes encoding the channel proteins), acidification is also impaired. Can you explain how Cl– channels might help acidification? According to your explanation, would the Cl– channels be absolutely required to lower the pH inside the endosome?
To study the mechanism of SERCA, you prepare membrane vesicles containing this protein oriented such that its ATP binding site is on the outer surface of the vesicle. To measure pump activity, you use an assay that detects the formation of inorganic phosphate in the medium. When you add calcium and ATP to the medium, you observe phosphate production for only a short period of time. Only after the addition of calcimycin , a molecule that makes membranes selectively permeable to calcium, do you observe sustained phosphate production. Explain.
Which of the following is true about motion of membrane lipids? A. They can move most rapidly when in the gel phase. B. Lateral diffusion is catalyzed by flippase proteins. C. To increase the fluidity of membranes at low temperatures, cells synthesize more saturated fatty acids and fewer unsaturated fatty acids. D. Transbilayer diffusion involves the transfer of lipids from one face of the bilayer to another.
Liposomes have long been investigated as drug delivery mechanisms in humans and animals, but only recently have they started to be used clinically in targeted cancer therapies and now, vaccines. Liposomes are simply vesicles with a phospholipid bilayer that contain an inner aqueous compartment. Hydrophilic compounds could be carried in the buffer inside the liposome or hydrophobic drugs within the membrane itself. For instance, the Moderna and Pfizer mRNA vaccines actually use liposome technology to deliver the SARS-CoV-2 spike mRNA to human cells. The liposomes fuse with the plasma membrane allowing the contents of the liposome to enter the cytosol of cells. Of course, once the mRNA is in the cytosol is can be translated to protein on a ribosome. Explain why nucleic acid won’t get through the plasma membrane on its own. Discuss the energetic restrictions to movement through the membrane
Many of the cell’s hydrolytic enzymes are located in the lysosome, where the pH is ∼5. What would you expect to be the optimum pH for these enzymes, and why would this protect the rest of the cell from the destructive power of these enzymes upon the accidental rupture of a lysosome?
Some scientists claim that prokaryotes like bacteria have membrane bound organelles, like chromatophores, anammoxosomes and magnetosomes. What really is the truth because it is widely known that prokaryotes do not have membrane bound organelles. Are these claims true or merely speculative? If this is true, what is the physiological basis for this?
Ca2+-ATPases are integral membrane proteins. They are active transport mechanisms that use the energy derived from ATP hydrolysis to pump calcium ions across the membrane. A specific form of Ca2+-ATPase, ERCA, is located on the endoplasmic reticulum membrane. In which direction does ERCA transport calcium ions? a.) ERCA transports calcium ions from the lumen of the endoplasmic reticulum into the cytoplasm. b.) ERCA transports calcium ions from the cytoplasm into the lumen of the endoplasmic reticulum.