Biology 1002B Lecture Notes - Lecture 17: Microrna, Rna Interference, Chloroplast

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erinfish440

15 Apr 2017

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Synthesis of all proteins being on cytosolic ribosomes . The synthesis of all proteins that are coded in the nucleus, begin their translation on free cytosolic ribosomes. Every mrna that comes out of the nucleus begins translation on free ribosomes in the cytoplasm. Organelle proteins are targeted for post-translational import via channels. Some proteins need to end up in the chloroplast. The genes for these proteins used to be in the chloroplast but they have been moved to the nucleus. So now these proteins are produced in the cytoplasm and need to be imported and they are sorted as a result of tags. The tag is a part of the protein and is recognized by transport proteins that enable that protein to be imported. Nuclear proteins are targeted for post- translational import through pores. Some proteins have to function in the nucleus so they need a nuclear tag.

Related Questions

6. True or false

a_______ Nuclear pore complexes are specialized so that some mediate import and others mediate export

b_______ Membrane-bound and free ribosomes, which are structurally and functionally identical, differ only in the proteins they happen to be making at a particular time.

c_______ Some proteins can be made as either free or membrane-bound proteins. They have the same mRNA but different splicing and poly-adenylation patterns

d_______ a protein that does not have a sorting signal will be tagged for destruction by ubiquitin

e_______ when the hydrophobic signal peptide emerges from the ribosome, it is bound by SRP, which causes a pause in protein synthesis. Synthesis resumes when the ribosome with a bound SRP then binds to the SRP receptor on the cytosolic surface of the rough ER.

f________ A protein cannot leave the ER unless it is correctly folded

g________ All of the glycoproteins and glycolipids in intracellular membranes have their oligosaccharide chains facing the cytosolic side, and all those in the plasma membrane have their oligosaccharide chains facing the outside of the cell.

29 Most proteins destined to enter the endoplasmic reticulum _________.

(a) are transported across the membrane after their synthesis is complete.

(b) are synthesized on free ribosomes in the cytosol.

(d) are keep binding to Signal recognition particle (SRP) while they are translated.

30 Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels?

(a) lysosome â endosome â plasma membrane

(b) ER â lysosome â plasma membrane

(d) ER â Golgi â plasma membrane

31 Which of the following statements about vesicle budding from the Golgi is false?

(a) COPII can initiate vesicle budding on Golgi membrane.

(b) Some vesicles budded from Golgi membranes move towards ER.

(d) Clathrin molecules act at the cytosolic surface of the Golgi membrane.

32 Which of the following statements is false?

(a) The signal sequences on mitochondrial proteins are first bound to translocator on outer membrane after translation.

(b) Most mitochondrial proteins are not imported from the cytosol but are synthesized inside the mitochondria.

(c) Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes.

(d) Mitochondrial proteins cross the membrane in their unfolded state.

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QUESTION 30

The function of centrosome is:

	1.	Microtubule initiation and organization in animal cells
	2.	Organization of thin filaments
	3.	Depolymerization of microtubules
	4.	Organization of intermediate filaments

2.5 points

QUESTION 31

The destinations of proteins synthesized on "free" ribomsomes include:

	1.	Endoplasmic reticulum
	2.	Nucleus
	3.	Mitochondria
	4.	Lysosomes

2.5 points

QUESTION 32

Microtubules can be assembled and disassembled quickly in response to the cellular changes is because:

	1.	Cells synthesize tubulin proteins very fast.
	2.	Cells can turn other cytoskeletal filaments into microtubules
	3.	Microtubules have an instable plus end and microtubules are probably organized by weak non-covalent interactions
	4.	The motor proteins of microtubules can organize the microtubules in response to the cellular changes

2.5 points

QUESTION 33

Both signal recognition particle and a translocon in rough endoplasmic reticulum membrane can recognize and bind to the signal sequence of a secretory protein, so they play the exact same role during protein co-translational translocation.

True

False

2.5 points

QUESTION 34

Rough endoplasmic reticulum is so named is because:

	1.	It has many proteins associated with its surface.
	2.	It has ribosomes associated with its cytosolic surface.
	3.	It is associated with nuclear membrane.
	4.	It has vesicles budding off its surface.

2.5 points

QUESTION 35

The membrane vesicles that transport materials between membrane compartments have a protein coat. The protein coat has similar functions in different vesicles. These functions include:

	1.	Help the enclosed material fold correctly.
	2.	Help degrade the protein in the vesicles
	3.	Maintain the internal pH of the vesicles
	4.	Function as mechanical device to form a vesicle and select the components to be carried by a vesicle.

2.5 points

QUESTION 36

Lysosomes are important for:

	1.	Receptor-mediated endocytosis.
	2.	Breaking down foreign particles brought into the cells by endosomes
	3.	Regulating the process of organelle turnover.
	4.	Protein trafficking between membrane compartments

2.5 points

QUESTION 37

Which of the following is correct about membrane biosynthesis?

	1.	Membranes are synthesized in Golgi Complex.
	2.	Membranes arise from preexisting endoplasmic reticulum membranes.
	3.	Membranes are synthesized on ribosomes.
	4.	Membranes of all organelles have the same composition of proteins and lipids, since they all originate from endoplasmic reticulum.

2.5 points

QUESTION 38

During skeletal muscle contractions, the shortening of the muscle fibers is because of:

		The shortening of the thin and thick myofilaments.
		The shortening of the cytoskeletal filaments.
		The kinesin proteins moving over microtubules.
		The actin and myosin filaments sliding over each other.

2.5 points

QUESTION 39

The assembly and disassembly of microtubules is regulated by rate of growth and shrinkage of the plus end.

True

False

2.5 points

QUESTION 40

The functions of Golgi complex include:

	1.	O-linked oligosaccharides and most of a cellâs complex polysaccharides are assembled in Golgi complex
	2.	Cis Golgi complex sorts proteins
	3.	Trans Golgi complex segregates proteins in different types of vesicles for dilevery.
	4.	N-linked oligosaccharides are further processed in Golgi complex

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Biology 1002B Lecture Notes - Lecture 17: Microrna, Rna Interference, Chloroplast

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