BIO120H1 Lecture : Notes taken during lecture

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redtermite204

26 Jan 2011

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BIO120H1 Full Course Notes

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Document Summary

Er has translocators embedded in membrane allow for proteins into lumen. From rough er to golgi apparatus to other organelles through vesicles. Proteins synthesized into lumen of er become part of inside of lysosome or inside of er or secreted outside of cell. Lumenal leaflet is similar to extracellular face of cell. Er is dynamic, a network of tubules that form connections and break old ones. In drawining mrna in blue and green ribosome; nascent polypeptide synthesizing er signal sequence first translated. constantly coming to er membrane and then leaving. Translocon in blue: closed until ribosome is bound to it, translaiting protein into lumen of er. The red signal sequence remains there in the membrane. cleaves er signal sequence : eventully degraded. D signal recognition particle first binds, then translocator channel holds onto it. pluses always on cytosol help predict whether n or c-terminus.

Related Questions

1. The histones that form the core of the nucleosome get into the nucleus by which of the following?

a) Passive diffusion through nuclear pores

b) Selective and facilitated active transport through nuclear pores

c) Ribosomes located in the nucleus synthetize histones in the nucleus

d) Histones are made at the ER membrane and then diffuse to the nucleus

2. Membrane proteins that belong to the golgi, lysosome, or plasma membrane first pass through which organelle before reaching their final subcellular destination?

a) The golgi apparatus

b) The smooth ER

c) The nucleus

d) The ER membrane

e) The ER lumen

3. Where in the cell would a ribosomal protein be located if it has had its nuclear export signal inactivated (non-functional or non-existent).

a) The protein would be found in the ER lumen

b) The protein would remain in the nucleus

c) The protein would be secreted

d) The protein would remain in the cytoplasm

e) The protein would be in the ER membrane

4. Where would be the final destination of a protein if it contained a NLS anywhere in the protein sequence (and which is exposed to the cytoplasm after protein folding) but also contained an ER signal sequence at the carboxy terminus?

a) The ER lumen

b) The nucleus

c) The cytoplasm

d) The inner nuclear membrane

e) The ER membrane

5. The sequence K-D-E-L serves as a retention/retrieval signal for ER proteins.

a) True

b) False

6. The following are true for both cell membrane proteins and secretory proteins EXCEPT?

a) Precursors of the mature proteins contain signal sequence.

b) Both types of proteins contain stop-transfer sequences

c) Both types of proteins enter the ER while being synthetized

d) Both types of proteins pas through the golgi apparatus

e) Both are carried by clatherin-coated vesicles

7. If you isolate a regulated secreted protein from a secretory/storage vesicle and inject it into the cytosol, is will?

a) Be secreted through channels in the plasma membrane

b) Be taken up into secretory vesicle and secreted

c) Remain in the cytosol until it is degraded

d) Be taken up into the rough ER and follow the secretory pathway

goldmanatee250

Compare synthesis of soluble proteins and membrane proteins on bound ribosomes. Give a detailed explanation of the signal sequence, the signal recognition particle, the SRP receptor, the translocon, and the signal peptidase.

Which of the following is true about targeting of a secretory proteins?

A. Binding of SRP to the signal peptide and the ribosome temporarily accelerates protein synthesis.

B. The newly synthesized polypeptides include a signal peptide at their carboxyl termini.

C. The signal peptide is cleaved off inside the mitochondria by signal peptidase.

D. The signal recognition particle (SRP) binds to the signal peptide soon after it appears outside the ribosome.

E. The signal sequence is added to the polypeptide in a posttranslational modification reaction.