BIOA01H3 Lecture Notes - Lecture 5: G2 Phase, Dna Polymerase Iii Holoenzyme, Helicase

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Note 5 and 6 bioa01 module 2. Protein targeting getting a protein to where it needs to be in a cell. First decision is influenced by where the protein was made. All nuclear-encoded proteins start on the free ribosomes in the cytoplasm: some proteins are completed on the free ribosomes in the cytoplasm, some proteins are completed on the ribosomes attached to the endoplasmic reticulum. The decision to move proteins to the rough er is encoded in the mrna: they have a signal peptide which is few amino acids in a row near the amino-terminus of the growing peptide. Proteins without signal peptide complete translation on free ribosomes: proteins destined for the double membrane organelles: nucleus, chloroplast, or mitochondria, proteins of cytosol. E. g. , microtubules, microfilaments, intermediate filaments: proteins of the peroxisome, once these proteins have finished translating, they dissociate from ribosome and move to the appropriate organelles. Have a few amino acids that serve as localization signals.

Related Questions

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.

orangeplatypus673

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

ochrecoyote721

Question 1

Light microscopes

	A.	typically provide more resolution than an electron microscope
	B.	work by reflecting electrons off the surface of an object being studied
	C.	use light and glass lenses to magnify an image

Question 2

In the plasma membrane, the phospholipid heads

	A.	are hydrophilic and face outward toward the aqueous solution on both sides of the membrane
	B.	are hydrophobic and face outward toward the aqueous solution on both sides of the membrane
	C.	are hydrophobic and face inward, shielded from water

Question 3

The nucleus of a cell

	A.	is surrounded by a single layer of membrane.
	B.	contains DNA
	C.	is the primary location of protein synthesis

Question 4

Which location in the cell is unlikely to contain ribosomes or ribosomal subunits?

A.		endoplasmic reticulum
B		plasma membrane
C.		Cytoplasm

Question 5

The main function of the rough endoplasmic reticulum is the production of

A.		membrane and proteins secreted by the cell
B.		mitochondria and proteins secreted by the cell
C.		hydrogen peroxide

Question 6

The Golgi apparatus

A.		is the site of glucose breakdown
B.		stores, modifies, and packages proteins
C.		strings together amino acids to produce proteins

Question 7

The function of mitochondria is

		A. cellular respiration
		B. photosynthesis
		C. lipid synthesis

Question 8

Which of the following statements about the cytoskeleton is false?

		A. The cytoskeleton helps to support cell
		B. Once laid down, the elements of the cytoskeleton are fixed and remain permanently in place
	C.	The cytoskeleton is composed of three types of fibers: microfilaments, microtubules, and intermediate filaments

BIOA01H3 Lecture Notes - Lecture 5: G2 Phase, Dna Polymerase Iii Holoenzyme, Helicase

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