BIOL 225 Multiple Choice Practice Questions

When chemical, transport, or mechanical work is done by an organism,what happens to the heat generated?

It is lost to the environment

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

It joins Okazaki fragments together

What can you infer about a high-molecular weight protein that cannot be transported into the nucleus?

It lacks a nuclear localization signal (NLS)

When ATP releases some energy, it also releases inorganic phosphate. What happens to the inorganic phosphate in the cell?

It may be used to form a phosphorylated intermediate

What is the function of the nuclear pore complex found in eukaryotes?

It regulates the movement of proteins and RNAs into and out of the nucleus

Steroids, such as cholesterol, are considered to be lipids because they

are not soluble in water

Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through

gap junctions

Which of the following would you expect of a eukaryote lacking telomerase?

a reduction in chromosome length in gametes

If you could engineer an activity into DNA polymerase to allow both strands to move in the direction of the replication fork,what would this additional activity be?

the ability to synthesize DNA in the 3' → 5' direction

A solution of starch at room temperature does NOT readily decompose to form a solution of simple sugars because

the activation energy barrier for this reaction cannot easily be surmounted at room temperature

According the induced fit hypothesis of enzyme catalysis,

the binding of the substrate changes the shape of the enzyme's active site

What happens when comparing an uncatalyzed reaction to the same reaction with a catalyst?

the catalyzed reaction will have the same ∆G

Some cells have several nuclei per cell. How could such a cell with multiple nuclei be explained?

the cell underwent repeated mitosis, but cytokinesis did not occur

You grow cells from dissociated heart tissue in a special bioreactor. After a period of time they begin to exchange electrical signals and contract or "beat." What structures are most likely to have formed?

gap junctions

What will happen to a red blood cell if it is placed into a beaker of pure water with no solutes?

the cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC

The region of a Drosophila embryo with the highest concentration of bicoid protein will develop into the

head

Meiosis involves the creation of haploid cells from diploid cells. The haploid chromosome number is created when

homologous chromosomes separate

Humans can digest starch but not chitin because

humans have enzymes that can hydrolyze the α-glycosidic linkages of starch but not the β-glycosidic linkages of chitin

What type of bond is directly involved in the formation of an α-helix?

hydrogen bonds between amino acid residues

What are prions?

misfiled versions of a normal protein that can cause disease

In E. coli, if RNA polymerase is missing ____, then transcription initiation would not occur at the appropriate initiation sites.

sigma

What is a major difference between mitosis and meiosis I?

sister chromatids separate in mitosis, and homologs separate in meiosis I

Suppose you have identified a type of lizard that seems to have acquired a mutation in which hindlimb are absent. Which gene, also responsible for the loss of limbs in snakes, may be mutated in this animal?

sonic hedgehog

Cell walls are used by many different organisms for protection from their environment and structural support. These cell walls must be insoluble in water; otherwise, they would dissolve the first time an organism got wet. Which of the following carbohydrates would you expect to be most soluble in water? (chitin, peptidoglycan, cellulose, starch)

starch

The ATP made during glycolysis and fermentation is generated by

substrate-level phosphorylation

What is the primary function of the Calvin cycle?

synthesizing simple sugars from carbon dioxide

Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend the life span of cultured human cells. How might adding telomerase affect cellular aging?

telomerase stops telomere shortening and delays cellular aging

How do the α and β forms of glucose differ?

their ring structure differ in the orientation of a hydroxyl group

A high concentration of bicoid protein at the opposite ends of a developing Drosophila embryo would result in the development of a

two-headed fly (the head develops where there is a high concentration of bicoid protein)

DNA double helices are soluble in water but insoluble in alcohol. How do these physical properties reflect the chemical structure of the molecule?

the charged phosphate groups and sugars of DNA "like" to interact with polar water molecules

What provides the energy for the polymerization reactions in DNA synthesis?

the deoxyribonucleoside triphosphate (dNTP) substrates

The bicoid gene product is directly responsible for ____ in a developing Drosophila embryo.

the establishment of the anterior-posterior axis

Bicoid mRNA is translated in

the fertilized egg

Enzymes that readily break starch apart cannot hydrolyze the glycosidic linkages found in cellulose. Why is this logical?

the geometry of the bonds is different, and the shapes of enzyme active sites are highly specific

Why is water capable of forming hydrogen bonds?

the hydrogen atoms carry partial positive charges, the oxygen atom carries a partial negative charge, it is highly polar

How can a gene be longer than an mRNA produced by that gene?

the introns have been removed during mRNA processing

According to the lac operon model proposed by Jacob and Monod, what is predicted to occur if the operator is removed from the operon?

the lac operon would be transcribed all the time

What is the difference between the leading strand and the lagging strand in DNA replication in bacteria?

the leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction

How does a regulatory protein with a helix-turn-helix motif, such as the lac repressor, recognize a specific DNA sequence?

the regulatory protein detects the portion of the base pairs that projects into the major groove of double-stranded DNA

If one wished to test the hypothesis that humans and rhesus macaque monkeys differ due to differences in the expression of a large set of shared genes, the technique to use would be

DNA microarray analysis

In the carbon fixation step of the Calvin cycle, ribulose-1,5,-bisphosphate (a five-carbon compound) is carboxylated to produce

2 three-carbon compounds as the first stable intermediate

A solution with a pH of 5.0 has how many more protons in it than a solution with a pH of 7.0?

100 times

For thousands of years, explorers have sought mythical waters that promote a long life. In modern times, the quest for extending the human life span continues. Current research points to changes in the mitochondrial electron transport chain and the proton gradient as a cause of aging. Can it be manipulated to increase longevity? A drug called DNP allows protons to freely pass through the inner membrane. The effect of DNP on the life span of mice is shown in the graph. Each point represents the death of a single mouse. At what age is the difference in survival between the DNP-treated and the untreated control the greatest?

120 weeks

Put the following steps of DNA replication in chronological order: 1. single-stranded binging proteins attach to DNA strands 2. hydrogen bonds between base pairs of antiparallel strands are broken 3. primate binds to the site of origin 4. DNA polymerase binds to the template strand 5. an RNA primer is created

2, 1, 3, 5, 4

Put the steps for this signal transduction pathway in the order they are most likely to occur: 1. a conformational change in the signal-receptor complex activates an enzyme 2. protein kinases are activated 3. a signal molecule binds to a receptor 4. target proteins are phosphorylated 5. second messenger molecules are released

3, 1, 5, 2, 4

If a double-stranded DNA sample were composed of 15 percent thymine, what would be the percentage of guanine?

35

If an organism normally has 40 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle?

40

During transcription, in which direction is RNA synthesized and in which direction is the DNA template "read"?

5' to 3' 3' to 5'

RNA is synthesized in the ____ direction by RNA polymerase using ____.

5' → 3'; the template DNA strand

If one strand of a DNA molecule has the sequence of bases 5'-ATTGCA-3', the other complementary strand would have the sequence

5'-TAACGT-3'

If one strand of a DNA molecule has the sequence of bases 5'-CTTGCA-3', the other complementary strand would have the sequence

5'-TGCAAG-3'

What are three post transcriptional modifications often seen in the maturation of mRNA in eukaryotes?

5'-capping; 3'-poly(A) tail addition; splicing

Upon chemical analysis, a particular polypeptide was found to contain 100 amino acids. How many peptide bonds are present in this protein?

99

Which molecule shown below contains an amino functional group but it NOT an amino acid?

A

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules? A + G = C + T A + T + G + T A = C G = T

A + G = C + T

During RNA processing, a ____ is added to the 3' end of the RNA.

A long string of adenine nucleotides (poly-A tail)

In what ways are a promoter and a start codon similar? In what ways are they different?

A promoter and a start codon are similar in that both are sequences of nucleic acids that are required to start important processes, and both determine the sites where the process will begin. The key differences are that the promoter is needed to start transcription and the start codon is needed to start translation. Also, the promoter is a DNA sequence only, and the start codon is a sequence found within an mRNA.

For the axoneme (part of a flagellum or cilium) shown, what would happen when ATP is added if the links connecting the microtubule sublets and the spokes connecting each doublet to the central pair of microtubules were missing?

Adjacent doublets would slide past one another but no bending would occur

In order to insert a human gene into a plasmid, both must

Be cut by the same restriction enzyme. Doing so will result in the formation of complementary sticky ends.

Polypeptides are assembled from

Amino acids

Which structural formula depicts a ribonucleotide?

B

Which answer correctly associates a process in cellular respiration with (1) what goes in and (2) what goes out? A. Citric acid cycle: (1) acetyl CoA, CO2; (2) NADH, ATP, and FADH2 B. Citric acid cycle: (1) acetyl CoA; (2) NADH, ATP, FADH2, and CO2 C. Glycolysis: (1) glucose, NADH; (2) pyruvate D. Pyruvate processing: (1) acetyl CoA; (2) pyruvate, NADH, and CO2

B. Citric acid cycle: (1) acetyl CoA; (2) NADH, ATP, FADH2, and CO2

Which of the following is true? A. a gene can only lead to one form of RNA B. one gene can allow for the production of different types of RNA C. RNA produces many genes D. genes lead to the production of RNA

B. one gene can allow for the production of different types of RNA

Which of the following statements about quorum sensing is NOT accurate? A. quorum sensing is cell-cell communication in bacteria B. quorum sensing is species-specific C. quorum sensing may result in biofilm formation on your teeth D. quorum sensing is particularly well studied because of its important in understanding interactions between bacteria and eukaryotes

B. quorum sensing is species-specific

What would be the consequence(s) for DNA synthesis if primase were defective?

Both leading and lagging strand synthesis would be incomplete

Which of the listed statements describes the results of the following reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy

C6H12O6 is oxidized and O2 is reduced

What physical property is associated with the chemical differences between saturated and unsaturated fats?

C=C bonds normally results in kinds that increase the spacing between fats and thus make unsaturated fats more fluid than saturated fats

Compare the molecular formula of a carbohydrate (CH2O)n with that of carbon dioxide (CO2). What does the presence of hydrogen atoms in carbohydrates indicate?

Carbohydrates are more reduced than carbon dioxide

What statements about pattern formation are true?

Cells receive molecular signals that communicate their position in relation to other cells; differential gene expression affects the developmental process in animals; positional information controls pattern formation; homeotic genes code for transcription factors that control the development of segment-specific body parts

Predict how a drug that inhibits histone deacetylase will alter gene expression.

Chromatin would stay condensed; transcription would be prolonged; amount of protein would increase

You have just sequenced a new protein found in the naked mole rat and observe that sulfur-containing cysteine residues occur at regular intervals. What is the significance of this finding?

Cysteine residues are involved in disulfide bridges that help form tertiary structure

Translation occurs in the ____.

Cytoplasm (ribosomes, the sites of translation, are in the cytoplasm)

What enzyme forms covalent bonds between restriction fragments?

DNA ligase

Activators bind to regulatory sequences in ____ and to ____ polymerase.

DNA, RNA

Which of the following in the graph below would be the same in either an enzyme-catalyzed or a non catalyzed reaction?

d

The RNA segments joined to one another by spliceosomes are ____.

Exons (expressed regions)

The bicoid gene is a type of ____ gene.

egg-polarity

How does the negative control of the lac operon by glucose function through inducer exclusion?

High glucose concentrations prevent the transport of lactose into the cell.

Why is it that bacterial ribosomes can begin translation before mRNA synthesis is completed, but eukaryotic ribosomes cannot?

In prokaryotes, transcription and translation take place in the cytoplasm. Prokaryotic cells lack a nuclear envelope.

Peptidoglycan forms sheets that stiffen the cell walls of bacteria. How is the formation of sheets possible?

Individual strands are joined by peptide bonds, a type of covalent bond.

How is a mutation in a bacterial cell that deletes three base pairs 10 base pairs upstream from the +1 site likely to affect transcription and why?

Initiation will be inhibited because sigma cannot bind to the promoter. The +1 site is the transcription site and the region 10 base pairs upstream is a region of the promoter critical for sigma binding and initiation.

Why is carbon so important in biology?

It can form a variety of carbon skeletons and host functional groups

RNA and proteins combine in cells to form structures called ribosomes. Ribosomes contain the active site for peptide bond formation. Based on their chemical structures, do you think protein or RNA molecules form the active site within the ribosome?

It could be either, because both molecules have catalytic properties

The operon model of the regulation of gene expression in bacteria was proposed by ____.

Jacob and Monod

What level of transcription would you predict for a gene whose promoter is heavily methylated?

Low transcription. Promoters in condensed DNA are inaccessible to transcriptional regulators.

You are characterizing the properties of a self-splicing ribozyme and obtain the following results: in the presence of Mg2+, self splicing occurs. However, in the absence of Mg2+, self-splicing does not occur. Which of the following hypotheses does this observation support?

Mg2+ is a cofactor for the ribozyme required for its function

During RNA processing, a ____ is added to the 5' end of the RNA.

Modified guanine nucleotide (5' cap)

In the graph shown, why does the reaction rate plateau at higher reactant concentrations?

Most enzyme molecules are occupied by substrate at high reactant concentrations

Which of the following membrane activities requires energy from ATP?

Movement of Na+ ions from a lower concentration in a cell to a higher concentration in the extracellular fluid

Which molecule becomes reduced in the following reaction? glyceraldehyde phosphate + NAD+ → diphosphoglycerate + NADH + H+

NAD+

Which molecule is reduced in the following chemical reaction? glyceraldehyde phosphate + NAD+ → diphosphoglycerate + NADH + H+

NAD+

In addition to ATP, what are the end products of glycolysis?

NADH and pyruvate

In the presence of a regulatory protein the lac operon is ____.

Not transcribed. The regulatory protein of the lac operon is a repressor.

How could alternative splicing allow two different species with the same number of genes to produce vastly different numbers of proteins?

One species could produce many different mRNA from each of their genes while another only produces one or a few. Alternative splicing alters the number of different transcripts that could be produced from a single gene.

What is a primary difference between PCR and traditional cloning procedures such as those used to clone the human growth hormone genome?

PCR eliminated the need for restriction enzymes, vectors, and cells

Which of the following processes includes all others? (osmosis, diffusion of a solute across a membrane, facilitated diffusion, passive transport)

Passive transport

You have a phospholipid bilayer with equal amounts of saturated and unsaturated phospholipids. After testing the permeability of this membrane to glucose, you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to the membrane's permeability to glucose?

Permeability to glucose will increase

Of the three modes of gene regulation (transcriptional control, translational control, and post-translational control), which is fastest in response time?

Post-translational control. Because this mode involves modification of an already synthesized protein, it is the fastest in terms of regulating the activity of the gene product.

Enzyme complexes that break down protein are called ____.

Proteasomes

Protein-phosphorylating enzymes' role in the regulation of gene expression involves ____.

Protein activation

One strand of a microRNA is loaded into a silencing complex named ____. The microRNA targets mRNA for either ____ or ____.

RISC, mRNA degradation, translational repression

What is the function of a spliceosome?

RNA processing

What name is given to the process in which pre-mRNA is edited into mRNA?

RNA processing

The nuclear membrane's role in the regulation of gene expression involves ____.

Regulating the transport of mRNA to the cytoplasm.

Predict what would happen to regulation of the lac operon if the lac gene were moved 50,000 nucleotides upstream of its normal location.

Regulation of the lac operon would stay normal.

What is not a component of the lac operon?

Regulatory gene

A logical prediction is that compared with rats born to mothers fed a healthy diet, the Hnf4a gene in rats born to a mother fed a protein poor diet would

Show a lower frequency of promoter-enhancer association

Spliceosomes are composed of ____.

Small RNAs and proteins

Which statements about the modification of chromatin structure in eukaryotes are true?

Some forms of chromatin modification can be passed on to future generations of cells; methylation of histone tails in chromatin can promote condensation of the chromatin; DNA is not transcribed when chromatin is packages tightly in a condensed form; acetylation of histone tails is a reversible process; acetylation of histone tails in chromatin allows access to DNA for transcription.

How does primary protein structure affect the function of protein enzymes?

Substrates interact with R-groups at the enzyme's active site

An aminoacyl-tRNA that enters the A site of the ribosome will next occupy which site?

The P site, then the E site.

Scientists have found that polypeptides which are normally synthesized in the endoplasmic reticulum in a cell (in vivo) are about 20 amino acids longer when they are synthesized in the lab (in vitro) by ribosomes not attached to the endoplasmic reticulum. What is a possible explanation for the greater length of these polypeptides?

The 20 amino acids serves as a signal (peptide) sequence that directs the forming polypeptides to the endoplasmic reticulum, where they are cleaved off during processing

Over the past decade, there has been great interest in developing a sustainable and renewable energy source that would displace our dependence on fossil fuels. Photosynthetic organs, like micro algae, are currently being used to produce biofuels. A promising group of organisms for biofuel production are micro algae like Chlamydomonas reinhardtii. When grown in full sunlight, however, they have a reduced yield of chemical energy per photon absorbed. What is likely happening to the absorbed light energy that is not being used to drive photosynthesis?

The energy is likely released from excited pigments in the form of fluorescence and/or heat

In gel electrophoresis, which of the DNA molecules is the shortest?

The furthest one. The shorter the DNA molecule, the farther it moves on the gel.

IPTG is a molecule with a structure very similar to lactose. IPTG can be transported into cells by galactoside permease and can bind to the lac repressor protein. However, unlike lactose, IPTG is not broken down by β-galactosidase. Predict what would occur to lac operon regulation if IPTG were added to E. coli growth medium containing no glucose or lactose.

The lac operon would be strongly induced. Once inside the cell, the IPTG will bind to the repressor, causing it to release from DNA. IPTG cannot be broken down, so its concentration will remain high. Finally, since glucose is absent, there will be no inducer exclusion to inhibit IPTG transport through the galactoside permeate transporter and no cAMP to activate CAP.

Regulatory proteins bind to ____.

The operator. Transcription is inhibited when a regulatory protein binds to the lac operon operator.

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?

The pH of the matrix increases

A patient was involved in a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water- equal to the volume of blood lost- is added to the blood directly via one of his veins. What will be the most probably result of this transfusion?

The patient's red blood cells will swell and possible burst because the blood has become hypotonic compared to the cells

An enzyme has a total of four active sites. When you denature the molecule and study its composition, you find that each active site occurs on a different polypeptide. Which of the following hypotheses does this observation support?

The protein has quaternary structure

Predict what would happen if the lac repressor were altered so it could not release lactose once lactose was bound to it.

The repressor could not bind to DNA.

In the lac operon, the repressor inhibits transcription when

The repressor is not bound to the inducer

Why does a mutation in a single operator sequence of a regulator only affect a single gene while a mutation in the repressor affects all the genes of the regulon?

The repressor of the region binds to every operator of the region, while each operator only controls the expression of the single gene immediately downstream of it.

In eukaryotes, the size of the primary transcript is generally ____ the gene in the template DNA strand.

The same length as. The primary transcript is an exact RNA copy of the DNA coding sequence.

In eukaryotes, what allows only certain genes to be expressed in certain types of cells?

The set of regulatory transcription factors

During initiation of translation, the initiator tRNA is placed in the P site leaving the A site open. Why is it important to leave site A available?

The site A must remain open at the end of initiation of translation so that the second codon might be read, a new incoming amino-acyl tRNA occupy it, and a new peptide bond be formed between the amino acids attached to the tRNAs in site P and A.

In addition to splicing, additional modifications at the 5' and 3' end are required to generate a mature mRNA. What is the significance of these modifications?

These modifications (5' cap and poly-A tail) allow the mRNA to be recognized by the protein synthesis machinery and protect it from degradation.

Eukaryotic cells manufacture cytoskeletal proteins, which help to maintain cell shapes and functions. What would you predict about these proteins?

They are manufactured on free ribosomes in the cytoplasm

What do restriction endonuclease do?

They cut DNA at specific sites, known as recognition sites, to produce DNA fragments useful for cloning.

What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?

Transcription

Of the three modes of gene regulation (transcriptional control, translational control, and post-translational control), which is most efficient in resource use?

Transcriptional control. It can stop gene expression at the earliest possible step, saving the most energy and materials for the cell.

What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?

Translation

Where would you expect to find these amino acids in a globular protein in aqueous solution?

Valine would be in the interior, and glutamine would be on the exterior of the globular protein (think polarity)

A mutation that inactivated a gene required for apoptosis in the digits of developing mice would result in

a mouse that retains webbing between its digits

You want to engineer a eukaryotic gene into a bacterial cell and have it expressed. What must be included in addition to the coding eons of the gene?

a bacterial promoter sequence

An allele is

a different version of a specific gene

Which type of disorder would be most difficult to correct by gene therapy?

a dominant disorder

A mutation that knocked out the proofreading function of DNA polymerase would result in

a higher-than-normal rate of DNA synthesis errors

What is an open reading frame (ORF)?

a long DNA sequence that is uninterrupted by stop codons

Pemphigus vulgaris is an autoimmune disorder in humans in which antibodies are produced against cadherins. The blistering of the skin and mucous membranes characteristic of this disorder is probably a result of

a loss in cell-cell adhesion

Cellulose is

a major structural component of plant cell walls

The region of a Drosophila embryo with a low concentration of bicoid protein will develop into the

abdomen

During signal transduction a G protein is

activated when GDP is exchanged for GTP

What mean of transport would most likely be used for moving a medium-sized molecule (like a monosaccharide or an amino acid) from a low concentration on the outside of a cell to a high concentration on the inside of a cell?

active transport through a "pump" protein

Plasmodesmata are cell-cell junctions that are found between

adjacent plant cells

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." The little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. After the disruption, when electron transfer and ATP synthesis still occur, what must be present?

all of the electron transport proteins and ATP synthase

Not long ago, it was believed that a count of the number of protein-coding genes would provide a count of the number of proteins produced in any given eukaryotic species. This is incorrect, largely due to the discovery of widespread

alternative splicing

Changing a single amino acid in a protein consisting of 325 amino acids would

always alter the primary structure of a protein, sometimes alter the tertiary structure of the protein, and sometimes affect its biological activity

There are 61 codons that each specify the addition of a specific amino acid, and three stop codons for which there is no corresponding amino acid. However, there are only about 40 tRNA molecules, representing 40 anticodons. How is that possible?

an anticodon forms hydrogen bonds with the codon; it must match the first two bases of the codon, but is less specific with respect to the third base

A dolphin has suffered a tear in the based of its dorsal fin. The aquarium director asks your advice on how to treat the dolphin's injury. Which treatment should you recommend?

an extracellular matrix patch

Eukaryotic proteins that are known to add specificity to polymerase-dependent RNA synthesis are known as

basal (general) transcription factors

Steroid hormones, such as glucocorticoids, bind to intracellular receptors. The hormone-receptor complex is transported into the nucleus, where it can directly affect gene expression. To get from the location where the receptor binds the hormone to the site of action of the hormone-receptor complex, the hormone-receptor complex must

be transported through the nuclear pore complex

Exposing the inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." The little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. These inside-out membrane vesicles will

become acidic inside the vesicles when NADH is added

Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be reddish yellow. What wavelengths of visible light are absorbed by this pigment?

blue and violet

How might a change of one amino acid at a site, distant from the active site of an enzyme, alter an enzyme's substrate specificity?

by changing the shape of an enzyme

Aminoacyl tRNA syntheses are enzymes that

catalyze loading of an amino acid onto the 3' end of a tRNA

When a cockroach is crushed, it creates a crunching sound. What carbohydrate is the most likely source of this sound?

chitin

HIV is a virus that causes AIDS. In the mid-1990s, researcher discovered an enzyme in HIV called protease. Once the enzyme's structure was known, researchers began looking for drugs that would fit into the active site and block it. If this strategy for stopping HIV infections were successful, it would be an example of what phenomenon?

competitive inhibition

What is the structural feature that allows DNA to replicate with high fidelity?

complementary pairing of the nitrogenous bases

What two types of defects does a cancerous cell possess?

defects that make proteins required for cell growth active and tumor suppressor genes inactive

What is the correct order of steps for one cycle of PCR?

denature DNA; anneal primers; extend primers

What is the strongest evidence that protein structure and function are correlated?

denatured (unfolded) proteins do not function normally

What process produces the gradient of bicoid protein in a fertilized egg?

diffusion

Which of the following most accurately describes what is happening along the electron transport chain in the figure?

each electron carrier alternates between being reduced and being oxidized

The bacterium Bacillus anthraces, known as anthrax, causes an often fatal disease that is also called anthrax. On November 7, 2001, the Senate Majority Leader's office received an anthrax-tainted letter. More than 30 Senate workers showed signs of exposure. The U.S. CDC recommends that anyone who might have been exposed to anthrax begin treatment with the antibiotic ciproflaxin, a DNA-synthesis inhibitor. Based on this information, for ciproflaxin to be useful, it most likely works

exclusively against bacterial DNA synthesis proteins

You have been asked to analyze a reaction that took place at a temperature of 300 K. ∆H was -150 and ∆S was +0.4. Is the reaction endothermic or exothermic?

exothermic (∆G = ∆H - T∆S)

What triggers the translation of bicoid mRNA?

fertilization of the egg

Some of the drugs used to treat HIV patients are competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately, the high mutation rate of HIV means that the virus rapidly acquires mutations with amino acid changes that make them resistant to these competitive inhibitors. Where in the reverse transcriptase enzyme would such amino acid changes most likely occur in drug-resistant viruses?

in or near the active site

Where is most of the water in this reaction produced? C6H12O6 (glucose) + 6 O2 → 6 CO2 + 6 H2O

in the electron transport chain

In a normal cellular protein, where would you expect to find a hydrophobic amino acid like valine?

in the interior of the folded protein, away from water

Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the amount of ATP in a cell would be expected to

inhibit the enzyme and thus slows the rates of glycolysis and the citric acid cycle

Although DNA is the main hereditary material in all life-forms, it lacks one important characteristic of being a candidate for the first life-form. Why have researchers rejected the idea that DNA was found in the first life-form?

it does not function as a catalyst

As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy?

it is used to establish and maintain a proton gradient

Why might a point mutation in DNA make a difference in the level of a protein's activity?

it might substitute a different amino acid in the active site

Why is ATP an important molecule in metabolism?

it provides energy coupling between exergonic and endergonic reactions

What would be the consequence(s) for DNA synthesis if DNA ligase were defective?

lagging strand synthesis would be incomplete; leading strand synthesis would be largely unaffected

What would happen to the proton gradient and ATP production during cellular respiration after a drug has inhibited the enzyme that combined acetyl-CoA and oxaloacetate to form citrate in the citric acid cycle?

less NADH production would create a weaker proton gradient and less ATP production

Glycolysis is inactive when cellular energy levels are ____; the regulatory enzyme, phosphofructokinase, is ____ by high levels of ATP.

low; inhibited

RNA processing converts the RNA transcript into ____.

mRNA

You have a distant cousin, age 4, who is always tired and fatigued and is not able to play games and sports like other healthy children. He most likely has an enzyme deficiency or defect associated with which intracellular organelle?

mitochondria

Assume you have ground up some leaf cells from a green plant. You then centrifuge the mixture to separate different organelles into "fractions." You find that organelles in one of the lighter fractions can produce ATP in the dark, whereas organelles in one of the heavier fractions can produce ATP in the light. The lighter fraction most likely contains ____ and the heavier fraction most likely contains ____.

mitochondria, chloroplasts

Researchers endeavored to explain how vesicular transport occurs in cells by attempting to assemble the transport components. They set up microtubule tracks along which vesicles could be transported, added vesicles, and added ATP (because they knew the transport process required energy). Yet, when they put everything together, there was no movement or transport of vesicles. What were they missing?

motor proteins

Researchers tried to explain how transport of vesicles occurs in cells by attempting to assemble the transport components. They set up tracks of microtubules along which vesicles could be transported, and they added vesicles and ATP (because they knew the transport process requires energy). Yet, when they put everything together, there was no movement or transport of vesicles. What were they missing?

motor proteins

Sodium-potassium pumps

move two potassium ions and three sodium ions while consuming an ATP for each cycle

Point mutations are referred to as missense, silent, frameshift, or nonsense when they change the protein-coding potential of a gene. What is another group of mutations that may have important consequences for gene expression?

mutations that exist outside coding sequences in regulatory regions

Ciproflaxin belongs to a family of antibiotics called quinolone. Researchers studying three quinolone added them separately to growing bacteria and then examined DNA synthesis rates over time compared to a culture not exposed to any drug. The results are shown in the figure below. Which antibiotic inhibited DNA synthesis most rapidly?

naladixic acid

Suppose a cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It should be a cell from

nearly any eukaryotic organism

In gel electrophoresis, DNA molecules migrate from ____ to ____ ends of the gel.

negative; positive

Based on your knowledge of the polarity of water molecules, the solute molecule depicted below that is surrounded by water molecules is most likely

negatively charged

The R-groups highlighted in gray are

non polar for both alanine and valine

Bonds between two atoms that are equally electronegative are

nonpolar covalent bonds

RNA and DNA are polymers made up of which of the following monomers?

nucleotides

The bicoid gene is transcribed by

nurse cells

Carbon is an important element for biology because

of the variety of carbon skeletons and functional groups that can be built on them

The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different?

other pigments absorb light in addition to chlorophyll a

In its mechanism, photophosphorylation is most similar to

oxidative phosphorylation in cellular respiration

Why do loss of function mutations in p53 often lead to mutations in other genes?

p53 normally functions as a tumor suppressor to stop the cell cycle after DNA damage occurs. p53 normally functions as the "master brake" on the cell cycle that arrests the cell cycle or induces apoptosis after DNA damage occurs. If that function is lost, these cells are very likely to continue to move through the cell cycle and mutations in other genes will not become efficiently repaired.

If pigments from a particular species of plant are extracted and subjected to paper chromatography, which of the following is the most believable result?

paper chromatography would separate the pigments from a particular plant into several bands of different colors

Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development?

pattern formation

Prions are unusually resistant to an enzyme called proteinase K which breaks proteins into their monomer building blocks. Which bonds are being broken?

peptide bonds between amino acids

The duplication of homeotic (Hox) genes has been significant in the evolution of animals because it

permitted the evolution of novel forms

What is a major difference between the extracellular matrix (ECM) of a plant cell and the ECM of an animal cell?

plant ECM is primarily carbohydrate in nature, whereas animal ECM is mainly proteins

The rate of translation can be slowed drastically when a translation initiation factor is phosphorylated in response to a sudden temperature increase or viral infection. In this case, the phosphorylated translation initiation factor is under ____ control, and the phosphorylation of this translation initiation factor leads to widespread ____ control.

post-translational; translational

The normal function of a tumor suppressor gene is to

prevent progression of the cell cycle unless conditions are right for moving forward

A cell with a predominance of free ribosomes is most likely

primarily producing proteins in the cytosol

What is the major difference between eukaryotic DNA replication and prokaryotic DNA replication?

prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication

A spaceship is designed to support human life for a multiyear voyage to a galaxy far, far away. Plants will be grown to provide oxygen and to recycle carbon dioxide. Since the spaceship will be too far from the Sun for photosynthesis, an artificial light source will be needed. If the power fails and lights go dark, CO2 levels will ____, until the astronauts can repair the system.

rise as a result of both human and plant respiration

DNA is synthesized through a process known as

semiconservative replication

A laboratory might use dideoxyribonucleotides to ____.

sequence a DNA fragment

The reason for differences in the sets of proteins expressed in a neuron and a liver cell of the same individual is that neurons and liver cells contain different

sets of regulatory proteins

H. V. Wilson worked with sponges to gain some insight into exactly what was responsible for holding adjacent cells together. He exposed two species of differently pigmented sponges to a chemical that disrupted the cell-cell interaction, and the cells of the sponges dissociated. Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. Wilson found the sponges reassembled into two separate species. The cells from one species did not interact or form associations with the cells of the other species. How would you explain the results of Wilson's experiments?

the molecules responsible for cell-cell adhesion differed between the two species of sponge

Imagine you've isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant?

the mutant will show low levels of gene expression

The pH of the inner thylakoid space has been measured, as have the pH of the stroma and of the cytosol of a particular plant cell. Which, if any, relationship would you expect to find?

the pH within the thylakoid is less than that of the stroma

If you were to add one of the eight citric acid cycle intermediates to the culture medium of yeast growing in the laboratory, what do you think would happen to their rates of ATP and CO2 production?

the rates of ATP production and CO2 production would both increase

Tonegawa and his colleagues were able to express β-globin in an antibody-producing cell that normally does not express β-globin. They achieved this result by splicing an enhancer from an antibody-producing gene into the protein-coding portion of the β-globin gene. They then introduced this recombinant gene into cultured antibody-producing cells. Predict what would occur if Tonegawa had mistakenly inserted the antibody gene enhancer in reverse orientation (backward) into the β-globin gene.

there would be little difference in the results for an enhancer in reverse orientation compared with an enhancer in normal orientation

David Pribnow studied the base sequences of promoters in bacteria. He found two conserved regiosn in these promoters (the -10 box and the -35 box). What is the function of these two regions of the promoter?

they bind the sigma subunit that is associated with RNA polymerase

A single layer of epithelial cells lines the small intestine. In the duodenum (the first section of the small intestine), these epithelial cells secrete large quantities of digestive enzymes. Which of the following features would be typical of these epithelial cells?

they contain large quantities of rough endoplasmic reticulum

Fatty acids usually have an even number of carbons in their structures. They are broken down by a process called beta-oxidation. The end products of this metabolic pathway are acetyl groups of acetyl CoA molecules. What si the most likely fate of the acetyl groups?

they directly enter the citric acid cycle

Why might retroviral vectors for gene therapy increase the patient's risk of developing cancer?

they might integrate recombinant DNA into the genome in ways that misrelate the expression of genes at or near the site of integration

Why are fermentation reactions important for cells?

they regenerate NAD+ so that glycolysis can continue to operate

In humans, xeroderma pigmentosum (XP) is a disorder of the nucleotide excision repair mechanism. These individuals are unable to repair DNA damage caused by ultraviolet light. Which of the following are the most prominent types of DNA lesions in individuals suffering from XP?

thymine dimers

What is the main purpose of the light-capturing reactions of photosynthesis?

to produce NADHP and ATP

Since dideoxy sequencing is based on the change termination, why are normal deoxynucleotides also included in the reaction?

to produce a range of DNA synthesis products that terminate at every occurrence of a particular base

Photosystem II (PSII) is a critical component of the photosynthetic machinery. The electrons of PSII are excited and transferred to electron carriers. Which molecule or structure do the PSII replacement electrons come from?

water

The electrons of photosystem II are excited and transferred to electron carriers. From which molecule or structure do the photosystem II replacement electrons come?

water

Imagine that you discover a bacterial operon involved in the synthesis of vitamin B12. This operon is regulated by a repressor protein that binds to an operator sequence. Vitamin B12 is the allosteric effector of the repressor-- the molecule that binds to the repressor to affect its activity. Predict how vitamin B12 will influence repressor activity.

when vitamin B12 binds to the repressor, the repressor cannot bind to the operator