BIOL 1010 Lecture Notes - Protein Structure, Small Nuclear Rna, Rna Splicing

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coffeesalmon272

4 Dec 2012

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Messenger rna for secretory proteins code for initial signal sequence of 16- 20 hydrophobic amino acids at the amino end of the newly forming polypeptide. When a ribosome beings to synthesizes a protein with a signal sequence, it moves to the er membrane by a mechanism that involves two other components. The signal recognition particle docks with the receptor and the ribosome thus becomes bound to the er. The ribosome continues protein synthesis and the leading end of the new polypeptide (n-terminus) threads into the cisternal space. The signal sequence is removed by an enzyme. Newly formed polypeptide is released from the ribosome and folds into its native conformation. In these cases translation is completed in cytosol. This receptor is part of a protein complex, here called a translocation complex, that also includes a membrane pore and a signal-cleaving enzyme: the srp is released, and the growing polypeptide translocate across the membrane.

Related Questions

please help me answer theses questions correctly

1/ Which of the following are required for one-pass transmembrane proteins?

I. N-terminal signal sequence

II. Binding of SRP to the SRP receptor

III. Presence of stop-transfer sequence

IV. Presence of start-transfer sequence

a) I and III

b) I, II, and III

c) II, III, and IV

d) I, II, III, and IV

___________________

2/ Which of the following statements about the signal-recognition particle (SRP) is FALSE?

a) The SRP binds to the ER signaling sequence after the entire protein has been translated by the ribosome.

b) The SRP cycles between the ER membrane and the cytosol.

c) The SRP is required for peptides destined for either the ER membrane or ER lumen.

d) The SRP recognizes the signal sequence at the N-terminus of the newly forming polypeptide.

______________________

3) t-SNARES are _____.

a) found on the cytosolic side of the vesicle membrane.

b) necessary for recognition and transport of proteins into the nucleus.

c) usually located on the target membrane.

d) necessary for vesicle formation.

ceruleanchimpanzee878

1. Which cytosolic factor is most likely to associate with the signal sequence of a protein that is targeted co-translationally to the ER?

A chaperone of the Hsp70 family

The translocation channel

The ribosome

Signal recognition particle (SRP)

Signal peptidase

2. What is the most likely fate of a protein with an N-terminal hydrophobic sorting signal and an additional internal hydrophobic domain of 22 amino acids?

The protein stays in the cytosol

The protein is transported to mitochondria

Because the protein has an N-terminal sorting signal, the protein is translocated all the way into the ER lumen

The hydrophobic domain is recognized as a transmembrane domain once it is in the translocation channel and released sideways into the membrane

The hydrophobic domain is cleaved off by signal peptidase

3. Which of the following statements best describes N-glycosylation? N-glycosylation refers to........

the addition of a pre-formed sugar tree to a serine or threonine present in the cytosolic domain of a protein

the addition of a pre-formed sugar tree to a phospholipid to make a glycolipid

the addition of individual sugars to selected amino acids on a protein

the addition of a pre-formed sugar tree to an asparagine residue found within the consensus sequence Asn-X-Ser/Thr in an ER lumenal domain of a protein

the addition of a pre-formed sugar tree to an asparagine residue found within the consensus sequence Asn-X-Ser/Thr in a cytosolic domain of a protein

4. What is the most likely fate of a protein in which a mutation has led to misfolding in the ER?

It is sequestered by the proteasome in the cytosol

It is first tagged with ubiquitin in the ER and then degraded by the proteasome in the cytosol

It is first moved out of the ER, tagged with ubiquitin in the cytosol and then degraded by the proteasome in the cytosol

It associates with many chaperones in the ER, which guarantee its correct folding

Its misfolded state is recognized by chaperones in the ER, which will induce the protein's degradation by the proteasome in the ER.

raspberrybeaver682

The vesicles that transport materials from donor membranes to acceptor membranes include:

	1.	COP-II coated vesicles
	2.	COP-III coated vesicles
	3.	COP-I coated vesicles
	4.	Clathrin coated vesicles

2.5 points

QUESTION 11

During skeletal muscle contraction, the roles of ATP include:

	1.	ATP is not required for forming the crossbridges between myosin and actin filaments.
	2.	ATP is utilized as a structural linker to mediate the interaction between myosin and actin filaments
	3.	Hydrolysis of ATP provides energy for myosin head to move along actin filaments and the binding of ATP to myosin head allows the detachment of myosin fromactin filaments.
	4.	ATP binds to actin filaments to drive the power stroke of myosin head.

2.5 points

QUESTION 12

One of the functions of smooth endoplasmic reticulum is

	1.	Synthesizing steroid hormone in the endocrine cells of the gonad and adrenal cortex
	2.	Serves as the starting point of the biosynthetic pathway
	3.	Synthesizing secretory proteins
	4.	Degrading cell debris

2.5 points

QUESTION 13

The function of COP-II coated vesicles is mainly:

	1.	Transporting materials from endosomes to Golgi complex
	2.	Moving materials from the ER to the ERGIC and Golgi complex.
	3.	Transporting materials from Golgi complex back to endoplasmic reticulum.
	4.	Involved in receptor-mediated endocytosis.

2.5 points

QUESTION 14

Which of the following processes is completed in rough endoplasmic reticulum?

	1.	Chaperones help misfolded proteins fold correctly.
	2.	Proteins that target to nucleus are synthesized in rough endoplasmic reticulum.
	3.	O-linked glycosylation occurs in rough endoplasmic reticulum.
	4.	Misfolded proteins are destructed in rough endoplamic reticulum.

2.5 points

QUESTION 15

Kinesin is the motor protein that coorporates with microtubules. It has the following functions:

	1.	It uses GTP as energy source.
	2.	It can hydrolyze ATP and use the energy to drive cargo along microtubules from minus end to plus end.
	3.	It has a globular head that can act as GTPase
	4.	The tail of kinesin is more diverse and binds to cargo

2.5 points

QUESTION 16

For correct segregation and trafficking, lysosomal proteins are tagged in the cis-Golgi with phosphorylated mannose residues, and then the tagged lysosomal enzymes are recruited to clathrin coated vesicles by mannose 6-phosphate receptors.

True

False

2.5 points

QUESTION 17

The process that specialized cells, such macrophages, engulf relatively large particles is:

	1.	Called pinocytosis
	2.	Called phagocytosis
	3.	Mediated by COP-II coated vesicles
	4.	Called autophagy

2.5 points

QUESTION 18

Proteins synthesized on rough endoplasmic reticulum and smooth endoplasmic reticulum are imported co-translationally to their destinations

True

False

2.5 points

QUESTION 19

Treatment of cells with a drug that promotes microtubule disassembly disperses Golgi complex into separate stacks of membrane compartments, suggesting that:

	1.	Golgi complex is made of microtubules.
	2.	Microtubules are important for the organization of Golgi complex.
	3.	Microtubules are transported into Golgi complex
	4.	Golgi complex is composed of tubulin proteins

2.5 points

QUESTION 20

Which of the following is correct about signal sequence of a secretory protein?

	1.	It is an âaddress codesâ for protein trafficking pathways
	2.	It is usually located at the C-terminus.
	3.	It targets the ribosome and the protein that is being synthesized to endoplasmic reticulum.
	4.	It is removed in Golgi complex.

apricotgrasshopper117

BIOL 1010 Lecture Notes - Protein Structure, Small Nuclear Rna, Rna Splicing

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