Chapter 4

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

All 64 possible triplet sequences in an mRNA are recognized by a nucleic acid molecule. true false

Protein families contain proteins with identical primary, secondary, and tertiary structures. true false

A cooperative effect often occurs in multi-subunit proteins, leading to improved function of the subunits when bound to each other. true false

Which one of the following is specific to the synthesis of only one type of protein? an aminoacyl tRNA synthetase a ribosome a messenger RNA an elongation factor a transfer RNA

Folding domains typically range in length from __________ amino acids. 50 to 80 1,000 to 1,500 10 to 20 200 to 275 25 to 100 or more

You are studying a protein that you call Protein X. There is an aspartic acid at a key position in Protein X which is important in the folding and stabilization of that protein. If this aspartic acid is changed to a different amino acid, which one of the following amino acid substitutions is most likely to allow the protein to fold normally? glutamic acid threonine glycine arginine serine

Which one of the following statements about translation in eukaryotes is incorrect? An initiator codon is identified by recognizing a 5' cap structure and scanning for the first AUG triplet. Translation continues until one of the three stop codons appears in the A site of the ribosome. A single processed mRNA can possess multiple protein coding regions. There are untranslated regions at both the 5' end and 3' end of a processed mRNA. All of these statements about translation in eukaryotes are correct.

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

Alpha helices are coils with how many amino acids per complete turn? 2.5 10 4.8 20 3.6

Which one of the following ribosomal subunits has three different pieces of rRNA in it? 50S 40S 60S 30S

The number of polypeptides possible with 50 amino acids would be calculated as 5020. true false

Proteins that prevent inappropriate folding of newly synthesized proteins are called _______. chaperones ribosomes enzymes polymerases synthetases

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? precursors of tRNAs bound to nucleotides, and not amino acids functional ribosomes that behave similarly to those found today precursors of tRNAs bound only to specific amino acids, such as glycine multiple polycistronic mRNAs, which could be translated to generate several proteins proteins with complex primary, secondary, and tertiary structures

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

Most proteins will retain metabolic activity when denatured. true false

Imagine that a primary RNA transcript from your favorite gene was processed incorrectly, such that it has no 5' cap. What would be the result? Translation would proceed normally. The initiation complex would fail to form properly, and translation would not occur. Termination would be affected, as release factors would be unable to bind to ribosomes. Translation would commence properly, but elongation would be severely affected. Translation would commence at an AUG site in the middle of the RNA sequence.

Which of the following is not a possible function of a protein-folding domain? catalysis ligand binding facilitation of interactions between proteins transfer of an amino acid to a ribosome transport of molecules across a membrane

Which of the following statements is true regarding glycine? Glycine is an asymmetric amino acid. Glycine is a large, polar amino acid. Glycine is a relatively "inflexible" amino acid. Glycine is similar to tyrosine in terms of structure and chemical properties. None of the above.

5'-AUG-3' is a codon that specifies what amino acid? Spell out the name of the amino acid completely.

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? No, most amino acid sequences cannot produce functional proteins. Yes, all possible amino acid combinations result in proteins, although many of these proteins have nearly identical structures. Yes, because most amino acid sequences actually produce functional proteins; however, many of these proteins are degraded in cells. No, even though all sequence combinations can result in functional proteins, it would be impossible to characterize all of them.

Which one of the following amino acids is capable of forming a disulfide linkage? cysteine arginine methionine isoleucine tyrosine

The platforms upon which protein synthesis takes place are called ______.

Imagine that a scientist is able to travel back in time to when the first proteins appeared. What would she not observe? Proteins would have relatively simple folding domains. Proteins would be long compared to proteins today. All proteins would be relatively short. Proteins would be long compared to proteins today and would possess several folding domains Proteins would possess several folding domains.

The bond between two amino acids is referred to as a(n) _____ bond.

Regardless of the amino acid to be added to a tRNA molecule, all tRNA molecules use the same sequence at their 3' end to serve as the amino acid attachment site. true false

Imagine that you have a unit of hemoglobin, a protein that is present in the aqueous environment of the human bloodstream. What type of folding domain does hemoglobin likely possess? TIM barrel β-barrel Rossman fold Globin fold either TIM barrel or β-barrel

All beta-sheet structures are comprised of protein strands running antiparallel to each other. true false

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

In metabolic processes that generate energy from six-carbon sugars like glucose, a molecule called NAD is often attached to an enzyme carrying out one of the metabolic reactions. Which one of the following folding domains is most likely to be found in the region of one of these enzymes where association with NAD occurs? TIM barrels globin folds Rossman folds beta barrels Rossman folds, TIM barrels, beta barrels and globin folds are all equally likely to be found in a metabolic enzyme in the region of attachment to NAD.

Secondary structures are stabilized by which type of interaction? disulfide linkages hydrophobic clustering hydrogen bonding ionic bonding van der Waals forces

Members of a protein family often contain the same folding domain. true false

How does a peptide bond form between amino acids? through the interaction between amino groups and carboxyl groups of adjacent amino acids through the interaction between hydrogen atoms of adjacent amino acids through the interaction between amino groups and R groups of adjacent amino acids through the interaction between water molecules and carboxyl groups of adjacent amino acids A peptide bond can form between any chemical groups of adjacent amino acids.

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? No, most amino acid sequences cannot produce functional proteins. Yes, all possible amino acid combinations result in proteins, although many of these proteins have nearly identical structures. Yes, because most amino acid sequences actually produce functional proteins; however, many of these proteins are degraded in cells. No, even though all sequence combinations can result in functional proteins, it would be impossible to characterize all of them.

Imagine that you have a unit of hemoglobin, a protein that is present in the aqueous environment of the human bloodstream. What type of folding domain does hemoglobin likely possess? TIM barrel β-barrel Rossman fold Globin fold

A consecutive sequence of codons following a start codon is called a _______. peptide genetic code reading frame gene template strand

Which one of the following types of proteins interacts directly with a stop codon? transcription factor release factor elongation factor initiation factor sigma factor

All changes in gene sequence are mutations, but not all mutations decrease or increase in frequency over time. true false

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? Statements 1) and 2) are both true. Statements 1) and 2) are both false. Statement 1) is true; statement 2) is false. Statement 1) is false; statement 2) is true.

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

Which of the following statements is true regarding the development of pyrimethamine resistance in malaria parasites? Full resistance to pyrimethamine occurred independently of any mutations in malaria-causing parasites. Full resistance to pyrimethamine is the result of four mutations that arose one at a time and together affected an enzyme present in malaria-causing parasites. Full resistance to pyrimethamine is the result of four mutations that arose concurrently and together affected an enzyme present in malaria-causing parasites. The exact mutations necessary for full resistance to pyrimethamine were the only mutations that occurred in the malaria parasite.

Which one of the following interactions is not a stabilizing force at the tertiary level of protein organization? an ionic bond between a positively charged side chain and a negatively charged side chain hydrogen bonding between a carbonyl oxygen of one peptide bond and an amide hydrogen of a nearby peptide bond hydrophobic clustering of non-polar side chains in the interior of a protein van der Waals interactions between side chains in close proximity disulfide linkages between cysteine residues

Which one of the following statements about amino acids is incorrect? At typical cellular pH, the side chains of basic amino acids are positively charged. The more glycines that are found in a polypeptide's primary sequence, the more flexible the backbone of that polypeptide. The bridge between cysteines that connects parts of a protein is a stable, but non-covalent interaction. A turn or kink in a protein is more likely to be induced by a proline than by a glycine. Not every amino acid is asymmetric.

You are studying a protein that you call Protein X. There is an aspartic acid at a key position in Protein X which is important in the folding and stabilization of that protein. If this aspartic acid is changed to a different amino acid, which one of the following amino acid substitutions is most likely to allow the protein to fold normally? glutamic acid threonine serine glycine arginine

Structurally and functionally related groups of proteins are referred to as: realms relatives domains spheres families

A change in the sequence of a gene is referred to as a(n) _________.

Which one of the following ribosomal subunits has three different pieces of rRNA in it? 30S 40S 60S 50S

It is actually the 16S rRNA component of a 30S ribosomal subunit which 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? 3′-UCCUCCA-5' 5′-AGGAGGU-3' 5′-UCCUCCA-3' 3′-UAC-5' 5′-UGGAGGA-3'

Which of the following processes occur in the cytoplasm of eukaryotic cells? transcription and translation DNA replication only DNA replication and transcription DNA replication, transcription, and translation translation only

Scientists often utilize compounds resembling nucleic acids called "morpholinos," which can effectively prevent translation of any part of an mRNA of interest. Which of the following statements is most likely true regarding morpholinos? Morpholinos bind to AUG codons downstream of the start/initiation codon. Morpholinos bind to the region upstream of the initiation codon. Morpholinos have the same sequence as the target mRNA. Morpholinos are complementary to the target mRNA sequence and bind to the region upstream of the initiation codon. Morpholinos are complementary to the target mRNA sequence.

The three-dimensional shape of a protein is determined by the primary, secondary, tertiary, and in many cases, the quaternary structure of the protein. The following sentence is taken from scientific articles on protein structure. Choose the level of protein structure that applies best to the sentence. "There are hydrogen bonds between peptide backbone components that form neither an α-helix nor a β-pleated sheet." Primary Secondary Tertiary Quaternary

The three-dimensional shape of a protein is determined by the primary, secondary, tertiary, and in many cases, the quaternary structure of the protein. The following sentence is taken from scientific articles on protein structure. Choose the level of protein structure that applies best to the sentence. "Hydrogen bonds between peptide backbone components form a distinct helical structure." Primary Secondary Tertiary Quaternary

The three-dimensional shape of a protein is determined by the primary, secondary, tertiary, and in many cases, the quaternary structure of the protein. The following sentence is taken from scientific articles on protein structure. Choose the level of protein structure that applies best to the sentence. "Hydrogen bonds between peptide 'backbone' amino groups and carboxyl groups of one polypeptide and the R-groups of another polypeptide, contribute to the overall function of the protein." Primary Secondary Tertiary Quaternary

Some amino acids are coded by as many as six different codons. Which of the following amino acids fall into this category? (More than one answer may be correct.) methionine tyrosine tryptophan serine leucine

Proteins can be used for which one of the following cellular roles? Cell signaling Structural support Biological catalysis Cell communication All of these choices are correct.

In the context of ribosomes, the Svedberg value 60S most likely represents: an intact bacterial ribosome. an intact eukaryotic ribosome. a large bacterial ribosomal subunit. a large eukaryotic ribosomal subunit. a small eukaryotic ribosomal subunit.

The three-dimensional shape of a protein is determined by the primary, secondary, tertiary, and in many cases, the quaternary structure of the protein. The following sentence is taken from scientific articles on protein structure. Choose the level of protein structure that applies best to the sentence. "Disulfide bonds formed between cysteines stabilize the overall structure of this protein isolated from the bacterium." Primary Secondary Tertiary Quaternary

Some amino acids are coded by just one codon. Which of the following amino acids fall into this category? (More than one answer may be correct.) methionine tyrosine tryptophan serine leucine

True or False: multiple ribosomes can be translating protein from a single mRNA simultaneously in a eukaryote, but the mRNAs being translated are monocistronic. True False

Alpha helices are stabilized by hydrogen bonds between amino acids that are ______ residues apart. 2 4 10 20 100

Proteins that do not refold properly after being heated generally require the assistance of which one of the following types of molecules in vivo? Polymerases Ribosomes Enhancers Chaperones Transferases

X-ray crystallography was used to determine the structure of: cholesterol. vitamin B12. myoglobin. insulin. All of these choices are correct.

Which one of the following would least likely be used during translation? Initiation factors Release factors Sigma factors Elongation factors All of the answer choices would be equally likely to be used during translation.

The three-dimensional shape of a protein is determined by the primary, secondary, tertiary, and in many cases, the quaternary structure of the protein. The following sentence is taken from scientific articles on protein structure. Choose the level of protein structure that applies best to the sentence. "Peptide bonds form between the monomers." Primary Secondary Tertiary Quaternary

Use the double-stranded DNA molecule below to answer the following question. The first pair of nucleotides (circled) is the start point of transcription Which of the following is the correct mRNA produced from the transcription of this DNA molecule? 5'-AUGAUCGGAUCGAUCCAU-3' 3'-AUGAUCGGAUCGAUCCAU-5' 5'-UACUAGCCUAGCUAGGUA-3' 3'-UACUAGCCUAGCUAGGUA-5'

Which one of the following would least likely be used during the initiation phase of translation? Elongation factors tRNA Small ribosomal subunits Initiation factors mRNA

Which one of the following codons is capable of terminating translation? UAG UAA UGA UAG and UAA All of these choices are correct.

Which one of the following steps in translation is not part of the elongation phase? Movement of the ribosome three bases closer to the 3' end of the mRNA Ejection of an uncharged tRNA from the E site of the ribosome Peptide bond formation Binding of initiator tRNA to AUG start codon Introduction of a charged tRNA into an unoccupied A site of the ribosome

Which one of the following amino acids has its R-group covalently linked to the amino group of the amino acid? Glycine Serine Cysteine Glutamic acid Proline

Use the double-stranded DNA molecule below to answer the following question. The first pair of nucleotides (circled) is the start point of transcription. Which of the following is the correct polypeptide assembled by the translation of the mRNA produced by the transcription of this DNA molecule? amino end - Met-Ile-Gly-Ser-Ile-His - carboxyl end amino end - Tyr-Leu-Ala-Arg-Lue-Val - carboxyl end carboxyl end - Met-Ile-Gly-Ser-Ile-His - amino end carboxyl end - Tyr-Leu-Ala-Arg-Lue-Val - amino end

Which one of the following amino acids is most likely to participate in hydrogen bonding with water? Alanine Asparagine Leucine Phenylalanine Valine

Which one of the following is a critical region of a tRNA molecule? Amino acid attachment site Anticodon loop Stop codon Amino acid attachment site and anticodon loop All of these choices are correct.

The molecule currently being investigated as a possible means of synthesis of the first proteins is: mRNA. DNA. tRNA. rRNA. aminoacyl tRNA synthetases.

Which one of the following cellular processes occurs in the nucleus of a eukaryote? Transcription RNA processing Translation Transcription and RNA processing All of these choices are correct.

An initiator codon in E. coli is identified by locating: a promoter sequence. the 5' cap structure. a Shine-Dalgarno sequence. a terminator sequence from the previous gene. an origin of replication.

The three-dimensional shape of a protein is determined by the primary, secondary, tertiary, and in many cases, the quaternary structure of the protein. The following sentence is taken from scientific articles on protein structure. Choose the level of protein structure that applies best to the sentence. "There are extensive ionic interactions between positively charged R-groups and negatively charged R-groups on the polypeptide." Primary Secondary Tertiary Quaternary

In which of the following ribosomal sites is there complete codon-anticodon base pairing? The A site only The P site only The A site and the P site The P site and the E site The A site, the P site, and the E site

rRNAs are transcribed in the: cytoplasm. nucleus. nucleolus. mitochondria. endoplasmic reticulum.