Answered: QUESTION NO. 1 Targeting a protein to…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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QUESTION NO. 1
Targeting a protein to be degraded within proteasomes usually requires ubiquitin. In the function of ubiquitin all of the following are true except:

A. ATP is required for activation of ubiquicin.

B. a peptide bond forms between the carboxyl terminal of ubiquitin and an ε-amino group of a lysine .

C. linkage of a protein to ubiquitin does not always mark it for degradation.

D. the N-terminal amino acid is one determinant of selection for degradation.

E. ATP is required by the enzyme that transfers the ubiquitin to the protein to be degraded

QUESTION NO. 2
Much of procollagen formation occurs in the endoplasmic reticulum and Golgi apparatus which requires signal peptide. All of the following statements about targeting a protein for the ER are true except.

A. signal peptide usually has a positively charged N-terminus and a stretch of hydrophobic amino acids.

B. signal peptide emerging from a free ribosome binds signal recognition particle (SRP).

C. signal peptide is usually cleaved from the protein before the protein is inserted into the ER membrane.

D. docking protein is actually an SRP receptor and serves to bind the SRP to the ER.

E. SRP and docking protein do not enter the ER lumen but are recycled.

QUESTION NO.3

All of the following statements about telomerase are correct except

A. the RNA component acts as a template for the synthesis of a segment of DNA.

B. it adds telomeric repeats to the 5'-ends of the DNA strands.

C. it provides a mechanism for replicating the ends of linear chromosomes.

D. it recognizes a G-rich single strand of DNA

E. it is a reverse transcripcase.

QUESTION NO. 4

Collagen is unusual in its amino acid composition and requires a wide variety of posttranslational modifications to convert it to a functional molecule. Because of the complexity of collagen synthesis, there are many diseases, resulting in structural weaknesses in connective tissue, caused by defects in the process. Scurvy leads to a less stable collagen lacking sufficient hydroxyproline. 4-Hydroxylation of specific prolyl residues during collagen synthesis requires all of the following except

A. Fe2+
B. a specific amino acid sequence at the site of hydroxylation.

C. ascorbic acid.

D. co-hydroxylation of lysine .

E. individual α-chains, not yet assembled into a triple helix

QUESTION NO. 5

Transcription of eukaryotic genes requires the presence of a promoter and usually the presence of enhancers. An enhancer

A. is a consensus sequence in DNA located where RNA polymerase first binds.

B. may be located in various places in different genes.

C. may be on either strand of DNA in the region of the gene.

D. functions by binding RNA polymerase.

E. stimulates transcription in both prokaryotes and eukaryotes.

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