Biology 2382B Lecture Notes - Lecture 4: Calreticulin, Peroxisome, Organelle

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9 Dec 2012

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Lecture 4: protein synthesis and transport (the endoplasmic reticulum) (chp 13: p. 533-539, 549-554) Newly made peptides must be directed to the correct destination. Typical mammalian cell = 10,000 proteins must be localized correctly to function where they are supposed to. Targeting - direct proteins to the right destinations (organelles) during or after synthesis. Sorting - direct proteins to the secretory pathway (er, golgi, lysosomes) Note: though slightly different meaning sometimes used interchangeably . Many proteins are synthesized just by cytosolic ribosomes . Those which are targeted to intracellular organelles such as (er), mitochondria, chloroplasts, peroxisomes, and nucleus (they have a specific signal sequence) Other proteins are synthesized by ribosomes attached to er (the rough er) . Those which reside in er, secreted proteins, and proteins which are targeted to. 2 major protein-sorting pathways are known non-secretory and secretory. Where a protein will function in the cell will determine where it will be synthesize (i. e. cytosol vs. er rough) .

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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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One effective learning strategy when trying to learn largeamounts of factual information is to group items, or âchunkâ. Youshould include all important structures of the cell (this includescell membrane and membrane adaptations as well as organelles).Examples of general categories could be location, function,morphology, etc. Your categorization groups must tell the viewersomething about the structures. Once your structures are groupedaccording to the characteristics they share, you should include ashort phrase about what differentiates them from each other withinthe group. Citation of your source material must be present.

List of Organelles:

Nucleus, Nuclear envelope/membrane, Nucleolus, Ribosomes,Endoplasmic reticulum, Golgi apparatus, Mitochondria, Plasmamembrane, Cytoskeleton, Transport/secretory vesicles,Phagosomes/endosomes-including sorting & recycling endosomes,Lysosomes, Peroxisomes, Lipid droplets, Glycogen granules

I started this assignment and was going to go withfunction and morphology. Below is what I have so far, but I'mhaving a difficult time coming up with a short phrase for each anddistinguishing between the organelles that can change shape/morphand those that cannot. I am open to changing the categories that Ihave chosen to chunk. I've never used this technique before so it'sa new concept for me.

Function

Protein Synthesis â Nucleus, Nuclear envelope, Nuclear porecomplex, Ribosomes, Rough endoplasmic reticulum, Golgi apparatus,Plasma membrane

Energy Production â Mitochondria, Lipid droplets, Glycogengranules

Transportation â Transport vesicles, Phagosomes,Cytoskeleton

Metabolism â Lysosomes aid in digestion, Peroxisomes oxidizefatty acids

Morphology

Ability to change shape â Mitochondria, Cell membrane, Nuclearenvelope,

Inability to change shape â Nucleus, Nuclear envelope,

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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 2382B Lecture Notes - Lecture 4: Calreticulin, Peroxisome, Organelle

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