BIOLOGY 2B03 Lecture Notes - Lecture 4: Signal Peptide, Organelle, Endoplasmic Reticulum

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skyhornet611

1 Sep 2020

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While protein transport to mitochondria and peroxisomes occurs post-translationally, transport to the er is co-translational --> transport is occurring while translation is in progress. Pathway is known as the secretory pathway because secreted proteins are synthesized in the. Er before vesicle-based transport carries them out of the cell. Er is bound by a single membrane that is continuous with outer membrane of the nucleus. Does not have its own genome, so all er related proteins are coded for in the nuclear genome. First destination for secreted proteins (synthesized in er and then transported to other locations like lysosomes, golgi apparatus, cell membrane and even secreted out of the cell. Membrane associated ribosomes synthesize secretory proteins --> travel through golgi apparatus and in vesicles to reach outside of the cell. Two types of translationally active ribosomes: free ribosomes that are not associated with the er (free in cytosol) and attached ribosomes that are associated to the er membrane.

Related Questions

1A. Which of the following statements about the endomembrane system is/are correct? (select all that apply)

A.	Secreted proteins are inserted into the ER as they are being made by ribosomes.
B.	the nucleus is surrounded by two phospholipid bilayers.
C.	"Free" ribosomes attach to the endoplasmic reticulum.
D.	Secreted proteins are moved from the ER to the Golgi by ribosomes

1B. Place these components of the endomembrane system into the correct order in respect to when they first function in the production of a secreted protein.

	Endoplasmic Recticulum (ER)
	Riibosome
	Nucleus
	Transport Vesicle
	Cell Membrane
	Golgi Apparatus

lilacgnat89

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

1a.) What do the vast majority of proteins routed through the secretory pathway have in common?

A. They will be secreted.

B. The are post-translationally targeted to their final destination.

C. They are initially post-translationally inserted into the endoplasmic reticulum (ER) lumen.

D. They are co-translationally inserted into the ER lumen.

1b.) Which of the following accurately describes targeting proteins to the mitochondrial matrix or the nucleus?

A. Both mitochondrial matrix and nuclear proteins are co-translationally targeted to their destinations.

B. Both mitochondrial matrix and nuclear proteins are folded only after they reach their destinations.

C. Proteins targeted to the nucleus are completely folded in the cytoplasm. Proteins targeted to the mitochondrial matrix are unfolded while being inserted into the mitochondria and are refolded within the matrix.

D. Proteins targeted to the mitochondrial matrix are completed folded in the cytoplasm. Proteins targeted to the nucleus are unfolded while being inserted into the nucleus and are refolded within the nucleus.

E. None of these statements are correct.

carmineplatypus255

BIOLOGY 2B03 Lecture Notes - Lecture 4: Signal Peptide, Organelle, Endoplasmic Reticulum

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