Cells often need to adjust the fluidity of their membranes in order to adapt to

Question

Cells often need to adjust the fluidity of their membranes in order to adapt to environmental conditions, particularly temperature. For example, a yeast cell on the surface or a grape will often need to adapt to temperature shifts from 37° to 16° C when the sunsets. When the environmental temperature drops, how would a cell increase the fluidity of its membranes? (Remember, a saturated fatty acid has no double bonds in the hydrocarbon tail.) Please Choose one & Explain why you chose that answer

(A) Synthesize lipids with longer, saturated fatty acid tails (B) Synthesize lipids with shorter, saturated fatty acid tails (C) Synthesize lipids with shorter, unsaturated fatty acid tails

Welcome to Meadowlark Biosciences Inc! (Company slogan: “cheap cheap cheap...”)You are assigned to conduct pre-clinical lab studies to investigate the effects of a drug candidate that specifically inhibits function of the protein Ran GAP, which triggers the small GTPase Ran to hydrolyze GTP, which converts Ran-GTP to Ran-GDP. In considering your preliminary hypotheses, you predict that: Please Choose one & Explain why you chose that answer

(B) Nuclear export by exportin proteins will be disrupted by Ran GAP inhibition (C) Both nuclear import and export will be disrupted by Ran GAP inhibition (D) Ran GAP inhibition will have little effect on nuclear import or export, because both importin and exportin require interactions with Ran-GTP (not Ran-GDP

Explanation / Answer

A.

Plasma membrane consists of lipids, proteins which are highly glycosylated. To adapt to the change in temperature membrane has to change its composition. Since proteins attached to it cannot change its composition because they have predetermined function which leaves the cells to change the composition of lipid present in the membranes. Lipids are made up of triacylglycerol. Triacylglycerol is made up of glycerol and three fatty acids.

At high-temperature, membrane becomes viscous due to the high quantity of saturated fatty acids but at low temperature to remain liquid membrane saturated fatty acid change to unsaturated fatty acid.

When cells is kept at low temperature saturated fatty acids of membrane get compressed as a result they press another molecule of saturated fatty acid which makes the membrane fragile and susceptible to breakage

But when unsaturated fatty are compressed due to low temperature the kinks in their tails push nearby phospholipids and thus maintains the fluidity

the answer is (C) Synthesise lipids with shorter, unsaturated fatty acid tails

2. Ran-GAP, which triggers the small GTPase Ran to hydrolyze GTP, which converts Ran-GTP to Ran-GDP in the cytosol.

Nuclear import receptor binds to GTP and transfers into the cytosol where Ran-GAP hydrolyzes Ran-GTP to Ran-GDP and release Nuclear import receptor, which is ready to bind to any other protein to be imported to the nucleus. Whereas in the during nuclear export, nuclear export receptor binds to cargo and then to Ran-GTP, Ran-GTP facilitate export of proteins from Nucleus to cytoplasm. Upon reaching cytoplasm Ran-GAP hydrolyses GTP into GDP and facilitate the release of protein exported from the nucleus.

SO answer will be C) Both nuclear import and export will be disrupted by Ran-GAP inhibition

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