BS 161 Exam #1

What did Frances Arnold and coworkers find in the article on enzyme engineering?

- Changing amino acids near the active site of the enzyme can completely change which chemicals the enzyme interacts with. - Changing amino acids near the active site of the enzyme can completely change which reaction the enzyme catalyzes. - Researcher can train enzymes to catalyze desirable reactions unprecedented in the biological world.

Based on the article, what do cytochrome P450 enzymes normally do in humans?

- Cytochrome P450 enzymes metabolize drugs. - Cytochrome P450 enzymes protect against the negative effects of toxins.

The structural diversity of carbon-based molecules is determined by which of the following properties?

- the ability of those bonds to rotate freely - the ability of carbon to form four covalent bonds - the orientation of those bonds in the form of a tetrahedron

As part of their normal function, many proteins bind to DNA briefly and then release it again. Which types of bonds might be involved in these transient protein-DNA interactions? (Select all that apply.) - van der Waals forces - ionic - covalent - hydrogen

- van der Waals forces - ionic - hydrogen

1. covalent bond 2. hydrogen bond 3. ionic bond A. an interaction of a hydrogen atom and an electronegative atom B. an interaction between oppositely charged ions C. electrons shared by atoms

1. C 2. A 3. B

Which one of the following represents the pH of a solution with the HIGHEST concentration of hydrogen ions? - 9.1 - 4.5 - 11.5 - 7.0 - 1.0

1.0

In DNA molecules, complementary base pairs always include one purine nucleotide and one pyrimidine nucleotide. In the DNA of certain bacterial cells, 16% of the nucleotides are adenine nucleotides. What are the percentages of the other nucleotides in the bacterial DNA?

16% thymine, 34% guanine, 34% cytosine

Which one of the following MOST accurately describes the ratio of oxygen to carbon to hydrogen in a simple 6-carbon sugar such as glucose?

1:1:2

Based on the primer on scale and approximation, the length of a ribosome is approximately ____ orders of magnitude smaller than the length of a eukaryotic cell and approximately ____ orders of magnitude larger than the length of an amino acid.

3, 2

An RNA transcript is synthesized in which direction?

5' to 3'

A template DNA strand contains the sequence 5'-ATGCTGAC-3'. The corresponding sequence in the RNA transcript is:

5'-GUCAGCAU-3'

Which of the following DNA molecules would be more stable under conditions of increasing temperature?

A DNA molecule that has more guanine and cytosine nucleotides

All organisms use which of the following molecules to carry out cellular work such as growth and moving stubtances?

ATP

Which of the following CORRECTLY describes the complementary base pairing of adenine in both DNA and RNA?

Adenine pairs with thymine in DNA and with uracil in RNA

Which one of the following can contribute to a protein's tertiary structure? - All of the other answer options are correct. - covalent bonding - hydrogen bonding - ionic bonding -van der Waal's forces

All of the other answer options are correct.

Which of the following are covalent bonds? - peptide bonds - All of these choices are correct. - glycosidic bonds - phosphodiester bonds

All of these choices are correct

Proteins can be used for which of the following cellular roles? - biological catalysis - cell communication - structural support - All of these choices are correct. - cell signaling

All of these choices are correct.

Imagine the substrate for an enzyme contains a hydroxyl group. Which amino acid side chain, if present in the binding site on the enzyme, could assist in binding the substrate to the enzyme by forming a hydrogen bond with the hydroxyl group on the substrate?

Asparagine

Imagine a lysine in the binding site of an enzyme forms a favorable ionic interaction with the substrate to help the substrate bind. Imagine this lysine is changed to a different amino acid. Which amino acid listed below is most likely to prevent the substrate from binding to the enzyme?

Aspartic acid

Why are nucleic acids well suited for information storage and transfer? Because sometimes the sugar is ribose and sometimes the sugar is deoxyribose. Because the phosphates have a negative charge and can from ionic interactions. Because nucleic acids have phosphodiester bonds in their backbone. Because each base has a unique hydrogen bonding pattern.

Because each base has a unique hydrogen bonding pattern.

Because of hydrogen bonding, water is uniquely suited for its central role in life. Many hydrophilic molecules interact freely with water, but a number of hydrophobic molecules are important for life, too. How does the interaction between water and hydrophobic molecules help to organize biological systems?

Because water molecules preferentially associate with each other, they force hydrophobic molecules to associate with each other and not with water molecules

At physiological pH, the ionized state of the carboxyl (COOH) group in the R group of aspartic acid is:

COO-

Which two functional groups are always found in amino acids? Amino and sulfhydryl Carbonyl and amino Carboxyl and amino Hydroxyl and carboxyl

Carboxyl and amino

Which structure represents a short polypeptide?

D.

A mutation in _____ results in a change in _____ that sometimes produces a(n) _____ with altered structure and function.

DNA; RNA; protein

Which one of the following entities does NOT possess the ability to synthesize its own proteins? - Archaea and Bacteria - Archaea - Eukarya - Bacteria and Eukarya - Eukarya and Archaea

Eukarya

Because there are four RNA nucleotides and each codon is three nucleotides long, there are 64 possible codons, each of which directs the ribosome to incorporate a different amino acid into a growing polypeptide chain.

False

During transcription of a given protein-coding gene, both strands are used as template.

False

The limitations of the genetic code are such that a single amino acid may be specified by no more than four codons.

False

When RNA is transcribed, the RNA/DNA complex extends for the entire length of the DNA sequence of interest

False

How will increasing the percentage of saturated fatty acids in a mixture of triacylglycerols impact the consistency of the mixture at room temperature? It will make it more solid. There is no biological basis on which to make this prediction. It will make it more liquid. It will not impact the consistency.

It will make it more solid.

Which best explains the potential of an enzyme to bind sugar X and not to sugar Y? It would be impossible for an enzyme to bind to the sugar X and not sugar Y because both sugars are polar. It would be impossible for an enzyme to bind to the sugar X and not sugar Y because both sugars are hydrophobic. It would be possible to for the enzyme to bind to sugar X and not sugar Y because differences in the orientation of a hydroxyl group allows for differences in hydrogen bonding. It would be possible to for the enzyme to bind to sugar X and not sugar Y because differences in the orientation of a hydroxyl group allows for differences in ionic interactions.

It would be possible to for the enzyme to bind to sugar X and not sugar Y because differences in the orientation of a hydroxyl group allows for differences in hydrogen bonding.

The function of a protein is dependent upon the shape into which the chain of amino acids folds. Many noncovalent interactions are responsible for maintaining the protein's shape. Assume you have isolated a protein from an organism in its proper shape, and you have treated it with an enzyme that selectively targets and breaks only the peptide bonds in the proteins. Would the protein retain its shape under these conditions?

No; while the noncovalent bonds determine the shape of a protein, the peptide bonds are required to hold the amino acids together.

_____ are the subunits of nucleic acids, and _____ are the subunits of proteins.

Nucleotides; amino acids

Recall that a carbon atom behaves as if it possesses four valence electrons. Given this information, what is the MOST likely structural formula for carbon dioxide (CO2)?

O=C=O

What is the name of the enzyme complex that forms at the start of transcription?

RNA polymerase

Which one of the following CORRECTLY lists the components necessary for eukaryotic transcription?

RNA polymerase, general transcription factors, DNA, and RNA nucleotides

In general, colder temperatures reduce the fluidity of the membrane, so cells will produce different molecules to maintain the proper degree of fluidity. How would the membrane change in response to colder temperatures?

The amount of unsaturated fatty acids would increase

If you were to compare the entropy of a dog to that of a bucket of water, which of the following statement would be TRUE? - The entropy of the bucket of water would be greater. - The entropy of the dog would be greater. - The entropy of the bucket of water and the entropy of the dog would be equal.

The entropy of the bucket of water would be greater.

Increased temperature causes proteins to denature. Which level of structure remains intact when a protein is denatured and why does this level of structure remain intact? The primary structure of the protein remains intact because the peptide bonds between amino acids are more stable than the interactions found in secondary and tertiary structure. The primary structure of the protein remains intact because hydrophobic clustering of many amino acid side chains away from water is is more stable than the interactions found in secondary and tertiary structure. The secondary structure of the protein remains intact because the hydrogen bonding between backbone atoms of amino acids in a local area is more stable than interactions found in primary and tertiary structure. The secondary structure of the protein remains intact because the ionic interactions between side chains of amino acids is more stable than interactions found in primary and tertiary structure.

The primary structure of the protein remains intact because the peptide bonds between amino acids are more stable than the interactions found in secondary and tertiary structure.

What important feature(s) of noncovalent bonds make(s) them so important to life?

They are weak in a cellular environment, so they can be made, broken, and reformed easily

Imagine that a researcher claimed to have created a genetically modified plant that produces twice as much energy as it harnesses from its environment. How could this be possible?

This is not possible because such a plant would violate the second law of thermodynamics

Amino acids with hydrophobic R groups are most often found buried in the interior of folded proteins

True

Observations allow scientists to draw tentative explanations called hypotheses.

True

Sixty-one of the 64 possible codons specify amino acids, whereas the other three are stop codons. Each of the 61 codons specifies just one amino acid.

True

Some amino acids are specified by just one codon, whereas others are specified by multiple codons.

True

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

True

Whichever DNA strand is transcribed, the RNA polymerase reads the template strand from 3′ to 5′

True

The ability of atoms to form bonds is due largely to electrons farthest from the nucleus. These electrons are called ______ electrons

Valence

You have discovered a gene that contains a 2000 nucleotide coding region. You have also discovered that this gene contains 2 introns. One intron is 200 nucleotides and the other is 300 nucleotides. What can you predict using this information? a. The gene contains three exons b. Its longest mature mRNA would be 2000 nucleotides c. Its longest mature mRNA would be 1500 nucleotides d. Its longest mature mRNA would be 1500 amino acids e. a and c

a and c

Which one of the following is NOT a component of a phospholipid?

a core of four fused carbon rings

What is the general structure of a nucleotide? a molecule with one oxygen atom and two hydrogen atoms for each carbon atom central carbon atom connected to an amino group, a carboxylate group, a hydrogen atom, and a side chain a molecule that contains mostly carbon atoms and hydrogen atoms a molecule containing a phosphate, a sugar, and a base

a molecule containing a phosphate, a sugar, and a base

Which of the following are true of both DNA and RNA? a. Both can participate in base pairing. b. Both use the nitrogenous bases A, T, C, and G. c. Both are used by the ribosome as a template for translation. d. All of the above. e. a and b.

a. Both can participate in base pairing.

Anti-codons are present: a. In the tRNA b. In the mature mRNA c. In the protein d. In exons e. In introns

a. In the tRNA

You have discovered a mutation in the promoter region of an important human gene. Which of the following is the best prediction? a. The gene would not be transcribed. b. The gene would be transcribed correctly, but the mRNA would not undergo splicing c. The gene would be transcribed, but the mRNA would not be translated. d. The gene would be transcribed, but the mRNA would not be poly-adenylated. e. The gene would be transcribed, but the mRNA would not be capped.

a. The gene would not be transcribed.

Carbohydrates and proteins are two types of macromolecules. Which functional characteristic of proteins distinguishes them from carbohydrates?

ability to catalyze biochemical reactions

Which of the following is a critical region of a tRNA molecule?

amino acid attachment site and anticodon loop

An intron is:

an RNA sequence that is removed during the processing of an RNA molecule in the nucleus

Which one of the following amino acids is MOST likely to participate in hydrogen bonding with water?

asparagine

If the sequence of one strand of DNA is: 5'-ATATCTCGGG-3', which of the following is the sequence of the other strand? a. 5'-ATATCTCGGG-3' b. 5'-CCCGAGATAT-3' c. 5'-GGGCTCTATA-3' d. 5'-TATAGAGCCC-3' e. None of these is correct.

b. 5'-CCCGAGATAT-3'

Which of the following is true of proteins? a. They are sometimes lipids. b. tRNAs participate in their synthesis. c. They contain a start and a stop codon. d. b and c e. a and c

b. tRNAs participate in their synthesis.

The three main groups, or domains, of organisms are

bacteria, archaea, and eukaryotes.

Helicase is an enzyme that separates the double helix of the DNA into two separate strands. How do you think helicase does this?

by breaking hydrogen bonds

Which of the following are present in proteins? a. tRNAs b. Start and stop codons c. Covalent bonds d. All of the above e. b and c

c. Covalent bonds

Which, of the following is/are true of eukaryotes? a. mRNA splicing occurs within the cytoplasm b. Transcription occurs within the cytoplasm. c. Translation occurs within the cytoplasm. d. a and b e. a and c

c. Translation occurs within the cytoplasm.

What do genes endcode? a. lipids and carbohydrates b. proteins and lipids c. proteins and mRNAs d. lipids and mRNAs e. lipids, proteins, mRNAs, and carbohydrates

c. proteins and mRNAs

A pair of shared valence electrons is referred to as a(n):

covalent bond

Of the following types of bonds between atoms, which is the STRONGEST? - ionic bond - covalent bond - hydrogen bond - van der Waals forces

covalent bond

Which of the following is true of amino acids? a. Their side chains enable amino acids to engage in intramolecular interactions b. There is at least one tRNA per amino acid. c. Amino acids are brought to the ribosome by tRNAs. d. All of the above. e. None of the above.

d. All of the above.

Which of the following is true of genes? a. All of the DNA within a chromosome consists of genes. b. They exist only in eukaryotes. c. They are made of amino acids. d. They are special regions of the DNA that are transcribed to mRNA. e. All of the above.

d. They are special regions of the DNA that are transcribed to mRNA.

Which of the following appear in the correct order, from largest to smallest? a. DNA, nucleotide, chromosome b. chromosome, nucleotide, gene c. cell, gene, chromosome, nucleotide d. cell, chromosome, gene, nucleotide e. None of the above

d. cell, chromosome, gene, nucleotide

Alternative splicing allows for:

different polypeptides to be made from a single gene.

Alternative splicing means that:

different spliced forms contain different combinations of exons

Is the following sentence accurate? If not, what would you change to correct it? "Proteins are synthesized by translation of mRNA, which occurs on ribosomes" a. Change "translation" to "transcription" b. Change "on ribosomes" to "in the nucleus" c. Change "mRNA" to "tRNA" d. Change "mRNA" to "genes" e. The statement is correct as is.

e. The statement is correct as is.

The ability of atoms to attract electrons is referred to as:

electronegativity.

Triacylglycerols are used primarily for:

energy storage.

In eukaryotes, activator proteins bind to _____; generalized transcription factors bind to _____.

enhancers; promoters

A major difference between eukaryotic cells and prokaryotic cells is that:

eukaryotic cells have a nucleus and prokaryotic cells do not.

In messenger RNA, the protein-coding sequence is present in:

exons.

You are studying a protein that you call Protein X. There is an aspartic acid at a key position in Protein X that 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

A pair of atoms joined by a polar covalent bond:

has a slight positive charge on one atom and a slight negative charge on the other

Lipid bilayers spontaneously form to orient the _____ tails _____ to minimize their contact with water.

hydrophobic; inside

Which one of the following biological polymers is defined by a physical property instead of a chemical structure?

lipids

Pyrimidine and purine bases are found in:

nucleic acids

In a double-stranded DNA molecule, the strands are said to be antiparallel because:

one strand runs 5' to 3' and the other 3' to 5'.

At some point in their life cycle, all cells have a _____, whereas not all cells have a(n) _____

plasma membrane; nuclear membrane

The unique properties of water are due to the _____ of water molecules and the ability of water to form _____ with other water molecules and with other polar molecules.

polarity; hydrogen bonds

Transcription starts at a _____ and ends at a _____.

promoter; terminator

Peptide bonds are characteristic of:

proteins

Translation is the process by which:

proteins are synthesized from RNA molecules.

In the spiral staircase analogy of DNA structure, each railing represents a _____ and each step represents a _____

sugar-phosphate backbone; pair of bases

Which of the following brings amino acids to the ribosome for use in translation?

tRNA

In the DNA sequence 5'-TGAC-3', the phosphodiester linkage between the guanine and the adenine connects:

the 3' end of the guanine to the 5' end of the adenine.

When a peptide bond is created between two amino acids:

the carboxyl group of the first amino acid is joined to the amino group of the second.

The energy before a chemical reaction and the energy after a chemical reaction is the same. This is an example of:

the first law of thermodynamics.

Which of the following is NOT a key feature of individual cells? - the presence of a plasma membrane - the ability to store and transit information using nucleic acids - the presence of a nucleus - the ability to harvest and transform energy from the environment

the presence of a nucleus

Which one of the following components of an amino acid differs from one amino acid to another?

the side chain

Which of the following cellular processes occurs in the nucleus of a eukaryote?

transcription and RNA processing

Nucleic acids are important information storage molecules present in virtually every cell. Which of the following process are carried out by a cell when it accesses that information in the DNA of the genes?

transcription and translation

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

translation only