Chapter 19 Review Quiz

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. Creutzfeld-Jacob syndrome, bovine spongiform encephalitis, and scrapie all seem to be variants of disease related to inappropriate folding of proteins. It seems that some infective proteins come into contact with normal proteins and induce the normal proteins to go wrong. What are the protein infective agents called?

Hormones correct incorrect

Prions correct incorrect

Haptoglobins correct incorrect

Cytokines correct incorrect

Albumins correct incorrect

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. The molecule possessing the anticodon and which carries amino acids to the site of protein synthesis is called:

A transposon correct incorrect

The first-class carrier protein correct incorrect

Ribosomal RNA correct incorrect

Transfer RNA correct incorrect

Messenger RNA correct incorrect

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. Degeneracy in the genetic code seems wasteful. Of what possible value could degeneracy be, when it allows or requires more than one possible codon for most amino acids?

Degeneracy prevents mutations which might result from changing the second base of the codon correct incorrect

In fact, all codons for a particular amino acid are the same correct incorrect

Degeneracy provides protection against some point mutations correct incorrect

Degeneracy refers to the fact that there are some codons which do not code for any amino acid correct incorrect

Degeneracy helps to prevent aberrant behavior among teenage biochemists correct incorrect

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. The genetic code is a triplet code, with four bases taken three at a time, giving 64 combinations, enough for 21 amino acids and then some. If it were a duplex code, how many amino acids could be coded for?

32 correct incorrect

16 correct incorrect

8 correct incorrect

4 correct incorrect

2 correct incorrect

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. During protein synthesis in prokaryotes, the first amino acid placed in the chain is usually N-formylmethionine. Speculate on a reason why plain methionine wouldn't work just as well.

Perhaps there is not enough non-formylated methionine available correct incorrect

N-formylmethionine prevents the 30S subunit from binding prematurely to the 50S subunit correct incorrect

There's really nothing special about N-formylmethionine. N-acetylmethionine could perform the same function correct incorrect

Leucine zippers prevent methionine alone from performing this function correct incorrect

N-formylmethionine placed at the beginning of the growing peptide chain may protect the growing chain during translation correct incorrect

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. During periods of rapid protein synthesis, the mRNA moves rapidly through a group of protein synthesizing structures called, collectively:

Endoplasmic reticulum correct incorrect

Golgi apparatus correct incorrect

Flagella correct incorrect

Polyribosomes correct incorrect

Nuclear pores correct incorrect

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. The anticodon on one tRNA which carries histidine to the site of protein synthesis is CAU. What was the corresponding set of bases in the gene of the DNA molecule which specified placement of histidine at that location?

AAA correct incorrect

GTA correct incorrect

GAU correct incorrect

CAT correct incorrect

CAU correct incorrect

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. Two of the codons which have traditionally been considered stop signals are now known to specify placement of unusual amino acids. Which ones?

β-alanine and ε-phospholysine correct incorrect

Glutamine and carboxyhistidine correct incorrect

Asparagine and thiothreonine correct incorrect

Selenocysteine and pyrolysine correct incorrect

Hydroxyproline and hydroxytryptophan correct incorrect

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. During transcription, movement of the tRNA-polypeptide from the amino acid site of the ribosome to the peptide site requires a source of energy in the form of:

GTP correct incorrect

cAMP correct incorrect

UTP correct incorrect

CDP correct incorrect

TTP correct incorrect

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. Determination of the primary structure of a peptide was once a laborious activity, requiring weeks or months of treatment of the peptide with Sanger's reagent, hydrolysis, and paper chromatographic analysis. The lucky graduate student can now use mass spectrometry to break a peptide apart and accurately analyze the fragments. The mass spectrometer gives very accurate information concerning:

The charge on individual particles correct incorrect

The identity of the amino acids present correct incorrect

The number of acidic and basic amino acids present in the polypeptide correct incorrect

The molecular weight of fragments of the peptide correct incorrect

The ultraviolet absorption spectrum of the peptide correct incorrect

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. Chloramphenicol is an antibiotic which is effective against many microorganisms. It interferes with translation by:

Releasing the partially-formed peptide before translation is complete correct incorrect

Hydrolyzing peptides prematurely correct incorrect

Preventing the peptidyl-tRNA from moving from the amino acid site to the peptide site of the ribosome correct incorrect

Causing misreading of the codes on mRNA correct incorrect

Interfering with aminoacyl-tRNA binding correct incorrect

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. If you had taken a biochemistry course in the 1960s, you might have learned that 61 of the 64 possible codons actually coded for placement of amino acids, and that there were some "nonsense" codons which didn't seem to direct placement of any amino acid. Now, of course, we know that all the codons are useful. What do those three nonsense codons actually do?

These three are the start and stop codons correct incorrect

These are extra codons which may be used in case of mutations correct incorrect

In fact, these may be nonsense codons. Their usefulness hasn't been proved correct incorrect

These three codons specify isomers of the branched chain amino acids correct incorrect

These three codons direct placement of glutamine and asparagine correct incorrect

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. Protein synthesis is more rapid in organisms in which mRNA has a shorter half life. Protein synthesis in humans is much slower than that in E. coli. Why would it matter to either organism whether protein synthesis were rapid or slow?

Our cells live in an environment where changes are rapid and dangerous correct incorrect

Human cells live in relatively challenging environments correct incorrect

Bacteria may need to respond rapidly to changes in their environments, so must synthesize protein more rapidly correct incorrect

Bacteria may need to degrade RNA rapidly correct incorrect

Bacterial cells live in relatively safe, unchallenging environments correct incorrect

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. The triplet group of bases which says, "Put this amino acid here" is called a/an:

Codon correct incorrect

Anticodon correct incorrect

Operator correct incorrect

Promoter correct incorrect

Initiator correct incorrect

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. Proteins may be separated by a number of techniques, including isoelectric focusing. In isoelectric focusing, an artificial pH gradient is used in an electrophoresis chamber, and proteins mixed in the gradient migrate to the regions of their isoelectric points and then stop. Suppose that you set up a gel containing a mixture of acidic and basic substances ranging in pH from 3 to 10, and that you added a mixture of proteins and allowed them to move to the regions where they stopped migrating (their isoelectric pH, or pI). If you sliced the gel and found the protein
you were purifying was present in a slice having a pH of 4, you could be pretty confident that this protein:

Contained more acidic amino acids than basic amino acids correct incorrect

Contained more basic amino acids than acidic amino acids correct incorrect

Contained no basic amino acids correct incorrect

Contained no acidic amino acids correct incorrect

Contained an equal number of acidic and basic amino acids correct incorrect

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. The complete set of proteins which can be synthesized by the organism's genome is called the:

Proteome correct incorrect

Genomic correct incorrect

Proteus correct incorrect

Nucleome correct incorrect

Ribosome correct incorrect

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. Zymogens are inactive precursor molecules, often of extremely active digestive enzymes which are produced in inactive form and then converted to the active enzyme by removal of a protein "keeper." The type of post-translational modification involved in this case is:

Complete hydrolysis correct incorrect

Proteolytic cleavage correct incorrect

Methylation correct incorrect

Phosphorylation correct incorrect

Formation of disulfide bonds between cysteine residues of the same or different chains correct incorrect

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. How many high-energy phosphate bonds need be broken to power inclusion of a single amino acid in a polypeptide?

Four correct incorrect

Three correct incorrect

Five correct incorrect

Two correct incorrect

One correct incorrect

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. What is the source of energy used by aminoacyl-tRNA synthetase to power the reaction which attaches an amino acid to its tRNA?

CTP correct incorrect

cAMP correct incorrect

UTP correct incorrect

ADP correct incorrect

ATP correct incorrect

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. Synthesis of both DNA and RNA start at the 5' end of the growing chain, or the 3' end of the template. Synthesis of protein, however, starts at the 5' end of the mRNA template. Of what value could this be to the organism?

This protects the growing polypeptide chain from hyperthermic denaturation correct incorrect

This happens only in prokaryotes; in an organism as complicated as eukaryotes, protein synthesis can start at either end correct incorrect

This makes it possible for transcription to begin while replication is still occurring correct incorrect

Information can feed back from protein to modify transcription correct incorrect

Translation can begin while transcription is occurring. This gives the organism a quick start at protein synthesis correct incorrect

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. EF-Tu is a motor protein which positions aminoacyl-tRNA complexes in the amino acid site of the ribosome. Its major function in translation is as:

A replication factor correct incorrect

An elongation factor correct incorrect

A transition factor correct incorrect

A factory worker correct incorrect

A termination factor correct incorrect

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. What does prokaryotic mRNA have that eukaryotic mRNA doesn't?

ATP sequences correct incorrect

Termination factors correct incorrect

Initiation factors correct incorrect

Shine-Dalgarno sequences correct incorrect

van der Waals forces correct incorrect