certain forms of Ras (which is lipid anchored to the cell membrane) can associat
ID: 3523883 • Letter: C
Question
certain forms of Ras (which is lipid anchored to the cell membrane) can associate with lipid rafts.
a. Discuss how the amount of cholesterol and fatty acid composition of phospholipid and sphingolipid can cause lipid rafts to be stiffer then the surrounding membrane. Rubric (2): correct amount of cholesterol and type of fatty acids are used to explain increased stiffness of the membrane.
b. In the figure at right, researchers fluorescently labeled N-RAS containing a G13V mutation (N-Ras(G13V)). They looked for fluorescence recovery after photobleaching (FRAP) in membranes with normal levels of cholesterol (panel A(a); top) and membranes that were cholesterol depleted (less cholesterol in membrane; panel A(b), bottom).
Which graph shows the greatest mobility of N-Ras (G13V)? Rubric (2):
c. Then, explain why mobility changed between normal and cholesterol depleted membranes based on your understanding of fluidity and the composition of lipid rafts. Rubric (3): explanation of the why decreased cholesterol affected mobility of RAS in the membrane (3).
e. Most cancer cells display high rates of glucose uptake. The mechanism of glucose uptake is the same as the intestinal epithelial cell we covered in lecture. Treatment of cancer cells with an inhibitor of the Na+/K+ ATPase has been shown to kill cancer cells. Explain why this treatment works being sure to first outline how glucose enters the cancer cell (correct transporter) and how inhibition of the Na+/K+ATPase would inhibit transport. Rubric (4): Explanation of normal transport of glucose into a cell is correct. Explanation for how inhibition of N/KATpase decreases transport is correct.
Spac.. Heading 1 Heading 2 Title Subtitle Subtle En Styles ms 600 id | 400 N-Ras(G13V) R 090 0 23 45 800 AP 400 chol dept 200 e (s)Explanation / Answer
Answer for question A
plasma membrane is the main component of cell which cover around the cells .It is layer of phospholipids (Two fatty acid and attached with the phosphoate head ) interwoven with cholesterol and protein.
so , cholesterol makes the membrane stiff enough to pass the certain molecule through the plasma membrae because cholesterol is tha amphipathic molecule which has hydrophilic and hydrophobic property at the same time . so , cholesterol OH group aligns with the phosphate head of the phospholipids and the rest of the portion will be associated with the fatty acid part of the membrane.Because of the unique shape of the cholesterol , steroid ring of cholesterol is closely attracted to the fatty acid chain on nearest phospholipid which make the immobilize outer surface of the membrane to pass the water soluble molecule through it .
phospholipids has phosphate head which is hydrophilic and and fattyacid is the hydrophobic in nature . so, outside the cell is fluid containing environment and inside the cell is also aqueous .phosphate head face both side means inside the cell and outside the cell environment which makes the membrane to pass the molecule through it .
Answer for b
Mobility increases upon cholesterol depletion which is shown in the grapb B ( bottom panel )
Answer for C
Ras is the lipid anchored protein which resides into the inner leaflet of plasma membrane and their mobility increases upon depletion of the cholesterol because the lipid raft domain will be dispersed in this case.
answer for e
Most of the cancer cells has the high glucose uptake activity and the transporters of this processes is GLUTs . Na+ K+ ATPses is very important ion channel / transmembrane tranporter which allows the cells for normal metabolism and function .Na+ K+ ATPases inhibitor which alters the ion transports which results into the programmed cell death (apoptosis) and this is why it is a potent treatment for cancer cells .
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