Chapter 4 Learning Curves

False

All ß sheets are comprised of protein strands running antiparallel to each other.

true

false

True

The energy to carry out the movement of a ribosome comes from GTP.

true

false

Selection

In a population of organisms, beneficial and harmful random mutations are retained or eliminated through the process of:

conservation

folding

translation

expression

selection

true

The sequence of amino acids in a protein is referred to as its primary structure.

true

false

reading frame

A consecutive sequence of codons following a start codon is called a:

template strand.

gene.

genetic code.

peptide.

reading frame.

domain

A region of a polypeptide that folds in a particular way, relatively independently of the rest of the molecule, is a folding:

region.

domain.

segment.

exon.

lariat.

chaperones

Proteins that prevent inappropriate folding of newly synthesized proteins are called:

synthetases.

chaperones.

enzymes.

ribosomes.

polymerases.

b

Which of the following processes occur in the cytoplasm of eukaryotic cells?

a.DNA replication and transcription

b.translation only

c.DNA replication, transcription, and translation

d.DNA replication only

e.transcription and translations

false

There is approximately the same number of protein families as there are folding domains.

true

false

c

Consider the following two statements about protein structure: 1 - All polypeptides have tertiary structure. 2 - All proteins have quaternary structure. Which of the two statements above is correct?

a.Statements 1 and 2 are both true.

b.Statements 1 and 2 are both false.

c.Statement 1 is true; statement 2 is false.

d.Statement 1 is false; statement 2 is true.

c

Which one of the following statements about translation in eukaryotes is incorrect?

a.An initiator codon is identified by recognizing a 5' cap structure and scanning for the first AUG triplet.

b.Translation continues until the ribosome comes to one of the three stop codons.

c.A single mRNA can possess multiple protein coding regions.

d.There are untranslated regions at both the 5' end and 3' end of an mRNA.

e.All of these choices are correct.

true

The frequency of mutations does not necessarily decrease or increase over time.

true

false

d

Which of the following statements about amino acids is incorrect?

a.The more glycines that are found in a polypeptide's primary sequence, the more flexible the backbone of that polypeptide.

b.A turn or kink in a protein is more likely to be induced by a proline than by a glycine.

c.Not every amino acid is asymmetric.

d.The bridge between cysteines, which connects parts of a protein, is a stable but non-covalent interaction.

e.At typical cellular pH, the R groups of basic amino acids are positively charged.

operon

A(n) ______ is a group of functionally related genes transcribed as a polycistronic mRNA from a single promoter to a single terminator.

false

For a folding domain that forms a sort of "fist" with certain amino acid R groups buried within and other R groups facing out, the hydrophobic R groups mainly face "out" and the hydrophilic R groups mainly face "in."

true

false

3.6

α helices are coils with how many amino acids per complete turn?

20

4.8

2.5

10

3.6

a

Folding domains show how structure relates to function because:

a.All of these choices are correct.

b.they create surfaces whose shape and charge allows them to interact with other folding domains.

c.they change the configuration of the polypeptide in such a way as to facilitate proper folding of other regions.

d.they create regions whose shape and charge can bind specific small molecules.

b

One of your friends has decided to make it his life's work to characterize all functional proteins, as he is convinced that all possible amino acid combinations can result in a protein. Is it possible to confirm his hypothesis in this way?

a.No, because even though all sequence combinations can result in functional proteins, it would be impossible to characterize all of them.

b.No, because most amino acid sequences cannot produce functional proteins.

c.Yes, because all possible amino acid combinations result in proteins, although many of these proteins have nearly identical structures.

d.Yes, because most amino acid sequences actually produce functional proteins; however, many of these proteins are degraded in cells.

a

Which of the following statements is true regarding the development of pyrimethamine resistance in malaria parasites?

a.All of these choices are correct.

b.Rare mutations in the target protein increased the level of resistance.

c.Continued use of pyrimethamine treatment caused these mutations to increase in frequency.

d.In time, multiple different mutations were brought together to increase the level of resistance.

e.Eventually the drug pyrimethamine became ineffective against malaria.

d

Imagine that a researcher was able to travel back in time, shortly after the appearance of the first RNAs on Earth. What would she find?

a.multiple polycistronic mRNAs, which could be translated to generate several proteins

b.proteins with complex primary, secondary, and tertiary structures

c.precursors of tRNAs bound only to specific amino acids, such as glycine

d.precursors of tRNAs bound to nucleotides, and not amino acids

e.functional ribosomes that behave similarly to those found today

c

Imagine that a primary RNA transcript from your favorite eukaryotic gene was processed incorrectly, such that it has no 5' cap. What would be the result?

a.Translation would commence properly, but elongation would be severely affected.

b.Translation would proceed normally.

c.The initiation complex would fail to form properly, and translation would not occur.

d.Translation would commence at an AUG site in the middle of the RNA sequence.

e.Termination would be affected, as release factors would be unable to bind to ribosomes.

release factor

Which one of the following types of proteins interacts directly with a stop codon?

transcription factor

sigma factor

elongation factor

initiation factor

release factor

e

Which of the following is not a possible function of a protein-folding domain?

a.catalysis

b.transport of molecules across a membrane

c.ligand binding

d.facilitation of interactions between proteins

e.transfer of an amino acid to a ribosome

e.

It is actually the 16S rRNA component of a 30S ribosomal subunit that is responsible for recognition of a Shine-Dalgarno sequence. Which one of the following sequences in the 16S rRNA would you predict is responsible for the interaction between a small subunit and mRNA?

a. 3'-UAC-5'

b. 5'-UCCUCCA-3'

c. 5'-UGGAGGA-3'

d. 5'-AGGAGGU-3'

e. 3'-UCCUCCA-5'

a

Binding sites for tRNA are located in:

a.the large ribosomal subunit.

b.the small ribosomal subunit.

c.both ribosomal subunits.

d.neither ribosomal subunit.

b

Which one of the following interactions is not a stabilizing force at the tertiary level of protein organization?

a. van der Waals interactions between R groups in close proximity

b. hydrogen bonding between the carbonyl oxygen of one peptide bond and an amide hydrogen of a nearby peptide bond

c.disulfide linkages between cysteine residues

d. hydrophobic clustering of non-polar R groups in the interior of a protein

e. an ionic bond between a positively charged R group and a negatively charged R group