Question

23. A protein called Ras is tethered (linked) to the plasma membranes of stem cells where it participates in signal transduction pathways that affect stem cell proliferation. Which of the following covalent modifications would be responsible for tethering (linking) the Ras to the membrane? A. Phosphorylation B. Glycosylation C. Lipid modification D. Ubiqutiylation E. Acetylation 24. What do transmembrane proteins in the peroxisome, nucleus, and mitochondria all have in common? A. They are all co-translationally inserted into the membrane B. They are all post-translationally inserted into the membrane their transmembrane spanning regions are composed of highly hydrophilic amino acius D. They do not use a protein translocator for membrane insertion E. They do not have anything in common 25. You are studying a disease that occurs in individuals when an ER transmembrane protein call D2R is not inserted into the ER membrane of neurons. You find that the D2R gene is transcri and the mRNA is exported out of the nucleus. You also notice that all other ER transmembra proteins are inserted into the ER membrane properly. Which of the following could stw be the cause of this disease? A The D2R gene has mutations in start/stop transfer sequences that prevent recognition by the ER protein translocator B. The 5' cap is not added to the D2R mRNA C. The ER protein translocator is not present in this cell D. A and Care both possible

Answer 1

Ans23) Lipid modification is responsible for linking the Ras protein to the membrane.So, option C is correct.

Explanation:

Ras protein family consists of lipid anchored proteins and their lipid modification is required for linking them to the cell membrane.