Question 1

Which statement is FALSE concerning ubiquitin?

Accepted Answer

A)  The sequence of this protein is highly conserved in prokaryotes. 
B)  This protein is covalently added to proteins targeted for degradation. 
C)  This protein is small (<100 amino acids). 
D)  This protein contains lysine residues. 
E)  This protein interacts with the 19S regulatory particle in proteasomes. 
A)  The sequence of this protein is highly conserved in prokaryotes. 
B)  This protein is covalently added to proteins targeted for degradation. 
C)  This protein is small (<100 amino acids). 
D)  This protein contains lysine residues. 
E)  This protein interacts with the 19S regulatory particle in proteasomes.

Question 2

The signal sequences that direct proteins to the nucleus are:

Accepted Answer

A)  always at the amino terminus of the targeted protein. 
B)  cleaved after the protein arrives in the nucleus. 
C)  glycosyl moieties containing mannose 6-phosphate residues. 
D)  not located at the ends of the peptide, but in its interior. 
E)  the same as those that direct certain proteins to lysosomes. 
A)  always at the amino terminus of the targeted protein. 
B)  cleaved after the protein arrives in the nucleus. 
C)  glycosyl moieties containing mannose 6-phosphate residues. 
D)  not located at the ends of the peptide, but in its interior. 
E)  the same as those that direct certain proteins to lysosomes.

Question 3

If a single tRNA was used to code for isoleucine, what would be the sequence of the anticodon?

Accepted Answer

To determine the sequence of the anticod

Question 4

The enzyme that attaches an amino acid to a tRNA (aminoacyl-tRNA synthetase):

Accepted Answer

A)  always recognizes only one specific tRNA. 
B)  attaches a specific amino acid to any available tRNA species. 
C)  attaches the amino acid at the 5' end of the tRNA. 
D)  catalyzes formation of an ester bond. 
E)  splits ATP to ADP + Pi. 
A)  always recognizes only one specific tRNA. 
B)  attaches a specific amino acid to any available tRNA species. 
C)  attaches the amino acid at the 5' end of the tRNA. 
D)  catalyzes formation of an ester bond. 
E)  splits ATP to ADP + Pi.

Question 5

If a glycosylated protein is purified from the ER, what would you expect to be TRUE about this protein?

Accepted Answer

A)  The glycosyl groups will contain very little mannose. 
B)  The glycosylations are likely to be N-linked. 
C)  The protein will still contain a signal sequence. 
D)  The protein will be targeted to lysosomes. 
E)  The protein will be an integral membrane protein. 
A)  The glycosyl groups will contain very little mannose. 
B)  The glycosylations are likely to be N-linked. 
C)  The protein will still contain a signal sequence. 
D)  The protein will be targeted to lysosomes. 
E)  The protein will be an integral membrane protein.

Question 6

Which statement is NOT evidence supporting the idea that ribosomes are ribozymes?

Accepted Answer

A)  rRNAs are highly conserved. 
B)  Experiments show that mutations in proteins cause resistance to antibiotics that inhibit protein synthesis. 
C)  Extraction of ribosomal proteins does not greatly affect peptidyltransferase activity. 
D)  Ribosomal RNA forms the structural core of the ribosome. 
E)  None of the statements is evidence supporting the idea. 
A)  rRNAs are highly conserved. 
B)  Experiments show that mutations in proteins cause resistance to antibiotics that inhibit protein synthesis. 
C)  Extraction of ribosomal proteins does not greatly affect peptidyltransferase activity. 
D)  Ribosomal RNA forms the structural core of the ribosome. 
E)  None of the statements is evidence supporting the idea.

Question 7

What is a distinguishing characteristic between Class I and Class II aminoacyl-tRNA synthetases?

Accepted Answer

A)  Class I enzymes are ligases, while Class II enzymes are lyases. 
B)  Class I enzymes have proofreading, while Class II enzymes do not. 
C)  Class I enzymes bind to specific nucleotides in tRNA substrates, while Class II enzymes do not. 
D)  Class I enzymes transfer amino acids to the 2´ OH, while Class II enzymes transfer amino acids to the 3´ OH. 
E)  None of the answers is correct. 
A)  Class I enzymes are ligases, while Class II enzymes are lyases. 
B)  Class I enzymes have proofreading, while Class II enzymes do not. 
C)  Class I enzymes bind to specific nucleotides in tRNA substrates, while Class II enzymes do not. 
D)  Class I enzymes transfer amino acids to the 2´ OH, while Class II enzymes transfer amino acids to the 3´ OH. 
E)  None of the answers is correct.

Question 8

Describe the possible outcomes that could occur because of a single base change in an mRNA.

Accepted Answer

A single base change in an mRNA can lead

Question 9

What signal is used to identify a protein for transport to the lysosome?

Accepted Answer

A)  phosphorylation of N-acetylglucosamine residues in the ER 
B)  phosphorylation of glucose residues in the ER 
C)  phosphorylation of mannose residues in the ER 
D)  phosphorylation of glucose residues in the Golgi apparatus 
E)  phosphorylation of mannose residues in the Golgi apparatus 
A)  phosphorylation of N-acetylglucosamine residues in the ER 
B)  phosphorylation of glucose residues in the ER 
C)  phosphorylation of mannose residues in the ER 
D)  phosphorylation of glucose residues in the Golgi apparatus 
E)  phosphorylation of mannose residues in the Golgi apparatus

Question 10

Which statement does NOT describe a general aspect of signal peptides?

Accepted Answer

A)  They are often found at the N-terminus of secreted proteins. 
B)  They contain 10-15 hydrophobic amino acids. 
C)  They contain one or more negatively charged residues. 
D)  They tend to form an $\alpha$-helical structure. 
E)  All of these are general aspects of signal pepides. 
A)  They are often found at the N-terminus of secreted proteins. 
B)  They contain 10-15 hydrophobic amino acids. 
C)  They contain one or more negatively charged residues. 
D)  They tend to form an $\alpha$-helical structure. 
E)  All of these are general aspects of signal pepides.

Question 11

What is the minimum number of tRNA molecules that could code for serine?

Accepted Answer

A)  one 
B)  two 
C)  three 
D)  four 
E)  six 
A)  one 
B)  two 
C)  three 
D)  four 
E)  six

Question 12

Ubiquitin is added to proteins targeted for degradation by formation of a(n):

Accepted Answer

A)  ester bond between the C-terminus of ubiquitin and a serine of the target protein. 
B)  thioester bond between the C-terminus of ubiquitin and a cysteine of the target protein. 
C)  amide bond between the C-terminus of ubiquitin and a lysine of the target protein. 
D)  ester bond between a glutamate of ubiquitin and a serine in the target protein. 
E)  thioester bond between a glutamate of ubiquitin and a cysteine in the target protein. 
A)  ester bond between the C-terminus of ubiquitin and a serine of the target protein. 
B)  thioester bond between the C-terminus of ubiquitin and a cysteine of the target protein. 
C)  amide bond between the C-terminus of ubiquitin and a lysine of the target protein. 
D)  ester bond between a glutamate of ubiquitin and a serine in the target protein. 
E)  thioester bond between a glutamate of ubiquitin and a cysteine in the target protein.

Question 13

Which compound is NOT utilized for protein degradation in eukaryotes?

Accepted Answer

A)  ATP 
B)  ubiquitin ligases 
C)  deubiquitinases 
D)  lon protease 
E)  proteasome 
A)  ATP 
B)  ubiquitin ligases 
C)  deubiquitinases 
D)  lon protease 
E)  proteasome

Question 14

Which statement describes a feature of the wobble hypothesis?

Accepted Answer

A)  A naturally occurring tRNA exists in yeast that can read both arginine and lysine codons. 
B)  A tRNA can recognize only one codon. 
C)  Some tRNAs can recognize codons that specify two different amino acids if both are nonpolar. 
D)  The "wobble" occurs only in the first base of the anticodon. 
E)  The "wobble" occurs only in the third base of the anticodon. 
A)  A naturally occurring tRNA exists in yeast that can read both arginine and lysine codons. 
B)  A tRNA can recognize only one codon. 
C)  Some tRNAs can recognize codons that specify two different amino acids if both are nonpolar. 
D)  The "wobble" occurs only in the first base of the anticodon. 
E)  The "wobble" occurs only in the third base of the anticodon.

Question 15

Addition of O-linked glycosylations occurs predominantly in which cellular compartment?

Accepted Answer

A)  the nucleus 
B)  the endoplasmic reticulum 
C)  the Golgi apparatus 
D)  lysosomes 
E)  endosomes 
A)  the nucleus 
B)  the endoplasmic reticulum 
C)  the Golgi apparatus 
D)  lysosomes 
E)  endosomes

Question 16

Which statement is TRUE about the sorting pathway for proteins destined for incorporation into lysosomes or the plasma membrane of eukaryotic cells?

Accepted Answer

A)  Binding of SRP to the signal peptide and the ribosome temporarily accelerates protein synthesis. 
B)  The newly synthesized polypeptides include a signal peptide at their carboxyl termini. 
C)  The signal peptide is cleaved off inside the mitochondria by signal peptidase. 
D)  The SRP binds to the signal peptide soon after it appears outside the ribosome. 
E)  The signal sequence is added to the polypeptide in a posttranslational modification reaction. 
A)  Binding of SRP to the signal peptide and the ribosome temporarily accelerates protein synthesis. 
B)  The newly synthesized polypeptides include a signal peptide at their carboxyl termini. 
C)  The signal peptide is cleaved off inside the mitochondria by signal peptidase. 
D)  The SRP binds to the signal peptide soon after it appears outside the ribosome. 
E)  The signal sequence is added to the polypeptide in a posttranslational modification reaction.

Question 17

Which statement is FALSE with respect to disruption of protein synthesis by puromycin?

Accepted Answer

A)  The antibiotic puromycin resembles the aminoacyl end of a charged tRNA. 
B)  Puromycin binds to the ribosomal P site and causes premature dissociation of the peptide from the ribosome. 
C)  The amine group of puromycin acts as a nucleophile. 
D)  Formation of peptide-puromycin causes premature chain termination. 
E)  Puromycin becomes covalently attached to the C-terminal end of the peptide being synthesized. 
A)  The antibiotic puromycin resembles the aminoacyl end of a charged tRNA. 
B)  Puromycin binds to the ribosomal P site and causes premature dissociation of the peptide from the ribosome. 
C)  The amine group of puromycin acts as a nucleophile. 
D)  Formation of peptide-puromycin causes premature chain termination. 
E)  Puromycin becomes covalently attached to the C-terminal end of the peptide being synthesized.

Question 18

The large structure consisting of a mRNA molecule being translated by multiple copies of the macromolecular complexes that carry out protein synthesis is called a:

Accepted Answer

A)  lysosome. 
B)  polysome. 
C)  proteosome. 
D)  ribosome. 
E)  synthosome. 
A)  lysosome. 
B)  polysome. 
C)  proteosome. 
D)  ribosome. 
E)  synthosome.

Question 19

When first synthesized, proinsulin has an additional leader or signal peptide at its amino terminus. This complete molecule is called preproinsulin and the signal peptide is cleaved off to give proinsulin. Briefly, what is the likely function of the signal peptide?

Accepted Answer

The signal peptide, also known as a lead

Question 20

Which enzyme, discovered by Stephen Ochoa, was used to help to determine codon composition based on varying concentrations of nucleotides in experiments?

Accepted Answer

A)  RNA polymerase II 
B)  reverse transcriptase 
C)  RNA replicase. 
D)  polynucleotide phosphorylase 
E)  DNA polymerase I 
A)  RNA polymerase II 
B)  reverse transcriptase 
C)  RNA replicase. 
D)  polynucleotide phosphorylase 
E)  DNA polymerase I

Exam 27: Protein Metabolism

Which statement is FALSE concerning ubiquitin?

The signal sequences that direct proteins to the nucleus are:

If a single tRNA was used to code for isoleucine, what would be the sequence of the anticodon?

The enzyme that attaches an amino acid to a tRNA (aminoacyl-tRNA synthetase):

If a glycosylated protein is purified from the ER, what would you expect to be TRUE about this protein?

Which statement is NOT evidence supporting the idea that ribosomes are ribozymes?

What is a distinguishing characteristic between Class I and Class II aminoacyl-tRNA synthetases?

Describe the possible outcomes that could occur because of a single base change in an mRNA.

What signal is used to identify a protein for transport to the lysosome?

Which statement does NOT describe a general aspect of signal peptides?

What is the minimum number of tRNA molecules that could code for serine?

Ubiquitin is added to proteins targeted for degradation by formation of a(n):

Which compound is NOT utilized for protein degradation in eukaryotes?

Which statement describes a feature of the wobble hypothesis?

Addition of O-linked glycosylations occurs predominantly in which cellular compartment?

Which statement is TRUE about the sorting pathway for proteins destined for incorporation into lysosomes or the plasma membrane of eukaryotic cells?

Which statement is FALSE with respect to disruption of protein synthesis by puromycin?

The large structure consisting of a mRNA molecule being translated by multiple copies of the macromolecular complexes that carry out protein synthesis is called a:

When first synthesized, proinsulin has an additional leader or signal peptide at its amino terminus. This complete molecule is called preproinsulin and the signal peptide is cleaved off to give proinsulin. Briefly, what is the likely function of the signal peptide?

Which enzyme, discovered by Stephen Ochoa, was used to help to determine codon composition based on varying concentrations of nucleotides in experiments?

The Foundations of Biochemistry

Water

Amino Acids, Peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

DNA-Based Information Technologies

Lipids

Biological Membranes and Transport

Biosignaling

Bioenergetics and Biochemical Reaction Types

Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, Nucleotides, and Related Molecules

Hormonal Regulation and Integration of Mammalian Metabolism

Genes and Chromosomes

DNA Metabolism

RNA Metabolism

Regulation of Gene Expression

Filters