Question

Question 2 Not yet answered Marked out of 1,0 Flag question Question text Proteins destined for the mitochondrial matrix must pass through the Select one: a. inner mitochondrial membrane b. intermembrane space c. outer mitochondrial membrane d. TOM complex e. All of these are correct. Question 3 Not yet answered Marked out of 1.0 Flag question Question text In nuclear transport: Select one: a. Nuclear pores allow proteins to freely move back and forth between the nucleus and cytoplasm. b. RanGAP and RanGEF are localized to different sides of the nuclear envelope (.e. In the cytoplasm or in the nucleus). c. Ran+GTP undergoes exchange to convert to Ran+GDP. d. GTP hydrolysis drives importin and exportin to cross the nuclear pore. e. Exportin releases cargo when it binds to Ran-GTP. Question 44 Not yet answered Marked out of 1.0 Flag question Question text The translocon orients the first transmem-brane domain so that the positive (+) flanking charge faces the and the negative (-) flanking charge faces the Select one: a. The transmembrane domain is oriented randomly b. cytoplasm; cytoplasm c. ER lumen; ER lumen d. ER lumen; cytoplasm e. cytoplasm; ER lumen Question 5 Not yet answered Marked out of 10 Flag question Question text Which type of coat forms on the plasma membrane to form endosomos? Select one: a. cadmium-coated vesicles b. clathrin-coated vesicles c. uncoated vesicles d. COPI-coated vesicles e. COPII-coated vesicles

Answer 1

2. The mitochondrial proteins synthesised in the cytoplasm are transported into the mitochondria by the TIM and TOM complexes present in the inner membrane and outer memberane of the mitochondria respectively. The TOM complex on the outer mitochondrial membrane recognises the signal sequences on the proteins and translocates the protein into the inter membrane space, while TIM translocates specific proteins across the inner mitochondrial membrane into the matrix. Thus the protein passes through all of these, last option is correct.

3. Option A is wrong as transport across nuclear pore is regulated by a set of proteins such as importin, exportin and involves GTP and GDP and does not occur freely.Option C is wrong as RAN GDP converts to RAN GTP in the presence of Guanidine exchange factor (GEF) and not the vice-versa, option E is wrong as Exportin releases cargo when RAN GTP is hydrolysed and not when it binds to RAN GTP. Option D is also wrong as GTP hydrolysis is required for release of cargo and not to drive importin and exportin.Therefore the correct option is B. that RAN GAP (GTPase activating protein) and RAN GEF are localised in different sides of the nuclear envelope. GEF is present in the nucleoplasm and converts RAN GDP converts to RAN GTP and RAN GAP is present in the cytoplasm and facilitates the hydrolysis of GTP for recycling of RAN GDP.

4.The translocon in most cases orients the first transmembrane domain such that the N terminal i.e positive end is in the ER lumen and the negative end is in the cytosol. However ultimately, there are proteins without signal sequences that adopt reverse orientation upon passing through the translocon and in case of membrane spanning proteins both the ends may face either the lumen or the cytoplasm. Orientation depends on the function of the protein.

5.Correct option is C. Clathrin coated vescicles pinch off from the plasma membrane to form endosomes.

COP1 and COP II coated vescicles are involved in transport between golgi and ER.