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Cell Biology Exam: Biochemistry - Final Exam Questions and Answers, Exams of Biochemistry

A comprehensive set of multiple-choice questions and answers covering key concepts in cell biology and biochemistry. It is designed to help students prepare for a final exam in this subject. The questions cover a wide range of topics, including the structure and function of organelles, macromolecules, dna replication, and enzyme kinetics. Well-organized and provides detailed explanations for each answer, making it a valuable resource for students seeking to solidify their understanding of these fundamental biological processes.

Typology: Exams

2024/2025

Available from 12/09/2024

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Cell Biology/Cell Exam Biochemistry: Final Exam

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  1. Which of the following choices best describes the role of the lysosome?

(a) transport of material to the Golgi

(b) clean-up, recycling, and disposal of macromolecules

(c) sorting of transport vesicles

(d) the storage of excess macromolecules

  1. are fairly small organelles that provide a safe place within the cell to

carry out certain biochemical reactions that generate harmful, highly reactive

oxygen species. These chemicals are both generated and broken down in the

same location.

(a) Nucleosomes

(b) Lysosomes

(c) Peroxisomes

(d) Endosomes

  1. Which of the following monomer building blocks is necessary to

assemble selectively permeable boundaries around and inside cells?

(a) sugars

(b) fatty acids

(c) amino acids

(d) nucleotides

  1. DNA and RNA are different types of nucleic acid polymer. Which of the following

is true of DNA but not true of RNA?

(a) It contains uracil.

(b) It contains thymine.

(c) It is single-stranded.

(d) It has 5′-to-3′ directionality.

  1. Because there are four different monomer building blocks that can be used to

assemble RNA polymers, the number of possible sequence combinations that

can be created for an RNA molecule made of 100 nucleotides is.

(a) 100

4

(b) 4

100

(c) 4 × 100

(d) 100/

  1. Macromolecules in the cell can often interact transiently as a result of

noncovalent interactions. These weak interactions also produce stable, highly

specific interactions between molecules. Which of the factors below is the most

significant in determining whether the interaction will be transient or stable?

(a) the size of each molecule

(b) the concentration of each molecule

(c) the rate of synthesis

(d) surface complementarity between molecules

  1. The first task you are assigned in your summer laboratory job is to prepare a

concentrated NaOH stock solution. The molecular weight of NaOH is 40. How

many grams of solid NaOH will you need to weigh out to obtain a 500 mL

solution that has a concentration of 10 M?

(a) 800 g

(b) 200 g

(c) 400 g

(d) 160 g

  1. Oxidation is the process by which oxygen atoms are added to a target molecule.

Generally, the atom that is oxidized will experience which of the following with

respect to the electrons in its outer shell?

(a) a net gain

(b) a net loss

(c) no change

(d) an equal sharing

  1. The potential energy stored in high-‐energy bonds is commonly harnessed when

the bonds are split by the addition of in a process called.

(a) ATP, phosphorylation.

(b) water, hydrolysis.

(c) hydroxide, hydration.

(d) acetate, acetylation.

The maximum velocity ( V max

) of an enzymatic reaction is an important piece of

information regarding how the enzyme works. What series of measurements

can be taken in order to infer the maximum velocity of an enzyme-‐catalyzed

reaction?

(a) the rate of substrate consumption after the system reaches equilibrium, for

several reactant concentrations

(b) the rate of product consumption shortly after mixing the enzyme and substrate

(c) the rate of substrate consumption at high levels of enzyme concentration

(d) the rate of substrate consumption shortly after mixing the enzyme and

substrate, for several substrate concentrations

  1. The synthesis of glutamine from glutamic acid requires the production of an

activated intermediate followed by a condensation step that completes the

process. Both amino acids are shown in the figure below.

In the condensation step, is displaced by.

(a) OH, NH

3

.

(b) ADP, NH 2

.

(c) ATP, NH 3

.

(d) phosphate, NH 3

.

  1. Which of the following statements is true?

(a) Peptide bonds are the only covalent bonds that can link together two amino acids

in proteins.

(b) The polypeptide backbone is free to rotate about each peptide bond.

(c) Nonpolar amino acids tend to be found in the interior of proteins.

(d) The sequence of the atoms in the polypeptide backbone varies between different

proteins.

  1. Which of the following is not true of molecular chaperones?

(a) They assist polypeptide folding by helping the folding process follow the most

energetically favorable pathway.

(b) They can isolate proteins from other components of the cells until folding is

complete.

(c) They can interact with unfolded polypeptides in a way that changes the

final fold of the protein.

(d) They help streamline the protein-folding process by making it a more

efficient and reliable process inside the cell.

  1. Coiled-‐coils are typically found in proteins that require an elongated

structural framework. Which of the following proteins do you expect to have

a coiled-‐coil domain?

(a) insulin

(b) collagen

(c) myoglobin

(d) porin

  1. Which DNA base pair is represented in the figure below?

(a) A-T

(b) T-A

(c) G-C

(d) C-G

  1. Energy required by the cell is generated in the form of ATP. ATP is hydrolyzed

to power many of the cellular processes, increasing the pool of ADP. As the

relative amount of ADP molecules increases, they can bind to glycolytic

enzymes, which will lead to the production of more ATP. The best way to

describe this mechanism of regulation is.

(a) feedback inhibition.

(b) oxidative phosphorylation.

(c) allosteric activation.

(d) substrate-level phosphorylation.

  1. Fred Griffith studied two strains of Streptococcus pneumonia, one that causes a

lethal infection when injected into mice, and a second that is harmless_._ He

observed that pathogenic bacteria that have been killed by heating can no longer

cause an infection. But when these heat-‐killed bacteria are mixed with live,

harmless bacteria, this mixture is capable of infecting and killing a mouse. What

did Griffith conclude from this experiment?

(a) The infectious strain cannot killed by heating.

(b) The heat-killed pathogenic bacteria “transformed” the harmless strain into a lethal

one.

(c) The harmless strain somehow revived the heat-killed pathogenic bacteria.

(d) The mice had lost their immunity to infection with S. pneumoniae.

  1. The human genome is a diploid genome. However, when germ-‐line cells produce

gametes, these specialized cells are haploid. What is the total number of

chromosomes found in each of the gametes (egg or sperm) in your body?

(a) 22

(b) 23

(c) 44

(d) 46

  1. Which of the following questions would not be answered by using karyotyping?

(a) Is the individual genetically female or male?

(b) Do any of the chromosomes contain pieces that belong to other chromosomes?

(c) Does the individual have an extra chromosome?

(d) Do any chromosomes contain point mutations?

  1. Although the chromatin structure of interphase and mitotic chromosomes is

very compact, DNA-‐binding proteins and protein complexes must be able to gain

access to the DNA molecule. Chromatin-‐remodeling complexes provide this

access by.

(a) recruiting other enzymes.

(b) modifying the N-terminal tails of core histones.

(c) using the energy of ATP hydrolysis to move nucleosomes.

(d) denaturing the DNA by interfering with hydrogen-bonding between base pairs.

  1. The N-‐terminal tail of histone H3 can be extensively modified, and depending on

the number, location, and combination of these modifications, these changes

may promote the formation of heterochromatin. What is the result of

heterochromatin formation?

(a) increase in gene expression

(b) gene silencing

(c) recruitment of remodeling complexes

(d) displacement of histone H

  1. You prepare bacterial cell extracts by lysing the cells and removing insoluble

debris via centrifugation. These extracts provide the proteins required for DNA

replication. Your DNA template is a small, double-‐stranded circular piece of DNA

(a plasmid) with a single origin of replication and a single replication termination

site. The termination site is on the opposite side of the plasmid from the origin.

Which of the following statements is true with respect to this in vitro replication

system?

(a) There will be only one leading strand and one lagging strand produced using this

template.

(b) The leading and lagging strands compose one half of each newly synthesized

DNA strand.

(c) The DNA replication machinery can assemble at multiple places on this plasmid.

(d) One daughter DNA molecule will be slightly shorter than the other.

  1. You have discovered an “Exo

” mutant form of DNA polymerase in which the

3 ′-‐to-‐ 5 ′ exonuclease function has been destroyed but the ability to join

nucleotides together is unchanged. Which of the following properties do you

expect the mutant polymerase to have?

(a) It will polymerize in both the 5 ′-to-3′ direction and the 3 ′-to-5′ direction.

(b) It will polymerize more slowly than the normal Exo

polymerase.

(c) It will fall off the template more frequently than the normal Exo

polymerase.

(d) It will be more likely to generate mismatched base pairs.

  1. Which diagram accurately represents the directionality of DNA strands at

one side of a replication fork? D

  1. The events listed below are all necessary for homologous recombination to occur

properly:

A. Holliday junction cut and ligated

B. strand invasion

C. DNA synthesis

D. DNA ligation

E. double-strand break

F. nucleases create uneven strands

Which of the following is the correct order of events during homologous

recombination?

(a) E, B, F, D, C, A

(b) B, E, F, D, C, A

(c) C, E, F, B, D, A

(d) E, F, B, C, D, A

  1. Consider two genes that are next to each other on a chromosome, as arranged in the

figure below.

Which of the following statements is true?

(a) The two genes must be transcribed into RNA using the same strand of DNA.

(b) If gene A is transcribed in a cell, gene B cannot be transcribed.

(c) Gene A and gene B can be transcribed at different rates, producing different

amounts of RNA within the same cell.

(d) If gene A is transcribed in a cell, gene B must be transcribed.

  1. The figure below shows a ribose sugar. The part of the ribose sugar where a new

ribonucleotide will attach in an RNA molecule is pointed to by arrow.

(a) 1.

(b) 3.

(c) 4.

(d) 5.

  1. Which of the following might decrease the transcription of only one specific gene in a

bacterial cell?

(a) a decrease in the amount of sigma factor

(b) a decrease in the amount of RNA polymerase

(c) a mutation that introduced a stop codon into the DNA that precedes the

gene’s coding sequence

(d) a mutation that introduced extensive sequence changes into the DNA that

precedes the gene’s transcription start site

  1. You have discovered a gene (Figure A below) that is alternatively spliced to produce

several forms of mRNA in various cell types, three of which are shown in Figure B

below. The lines connecting the exons that are included in the mRNA indicate the

splicing. From your experiments, you know that protein translation begins in exon 1.

For all forms of the mRNA, the encoded protein sequence is the same in the regions of

the mRNA that correspond to exons 1 and 10. Exons 2 and 3 are alternative exons

used in different mRNA, as are exons 7 and 8. Which of the following statements

about exons 2 and 3 is the most accurate?

(a) Exons 2 and 3 must have the same

number of nucleotides.

(b) Exons 2 and 3 must contain an integral

number of codons (that is, the number of

nucleotides divided by 3 must be an

integer).

(c) Exons 2 and 3 must contain a number of

nucleotides that when divided by 3, leaves

the same remainder (that is, 0, 1, or 2).

(d) Exons 2 and 3 must have different

numbers of nucleotides.

  1. Which of the following molecules is thought to have arisen first during evolution?

(a) protein

(b) DNA

(c) RNA

(d) all came to be at the same time

  1. Investigators performed nuclear transplant experiments to determine whether

DNA is altered irreversibly during development. Which of the following

statements about these experiments is true?

(a) Because the donor nucleus is taken from an adult animal, the chromosomes

from the nucleus must undergo recombination with the DNA in the egg for

successful development to occur.

(b) The embryo that develops from the nuclear transplant experiment is

genetically identical to the donor of the nucleus.

(c) The meiotic spindle of the egg must interact with the chromosomes of the

injected nuclei for successful nuclear transplantation to occur.

(d) Although nuclear transplantation has been successful in producing embryos in

some mammals with the use of foster mothers, evidence of DNA alterations

during differentiation has not been obtained for plants.

  1. Which of the following statements about transcriptional regulators is false?

(a) Transcriptional regulators usually interact with the sugar–phosphate backbone

on the outside of the double helix to determine where to bind on the DNA

helix.

(b) Transcriptional regulators will form hydrogen bonds, ionic bonds, and

hydrophobic interactions with DNA.

(c) The DNA-binding motifs of transcriptional regulators usually bind in the major

groove of the DNA helix.

(d) The binding of transcriptional regulators generally does not disrupt the

hydrogen bonds that hold the double helix together.

Note: Questions 33 to 34 use the following information and the data in the figure

below.

You are interested in understanding the gene regulation of Lkp1, a protein that is

normally produced in liver and kidney cells in mice. Interestingly, you find that

the LKP1 gene is not expressed in heart cells. You isolate the DNA upstream of the

LKP1 gene, place it upstream of the gene for green fluorescent protein (GFP), and

insert this entire piece of recombinant DNA into mice. You find GFP expressed in

liver and kidney cells but not in heart cells, an expression pattern similar to the

normal expression of the LKP1 gene. Further experiments demonstrate that there

are three regions in the promoter, labeled A, B, and C in the figure below, that

contribute to this expression pattern. Assume that a single and unique

transcription factor binds each site such that protein X binds site A, protein Y

binds site B, and protein Z binds site C. You want to determine which region is

responsible for tissue-‐specific expression, and create mutations in the promoter

to determine the function of each of these regions. In the figure below, if the site is

missing, it is mutated such that it cannot bind its corresponding transcription

factor.

  1. Which of the following proteins is likely to act as a gene repressor?

(a) factor X

(b) factor Y

(c) factor Z

(d) none of the above

  1. Which of the following proteins are likely to act as gene activators?

(a) factors X and Y

(b) factors X and Z

(c) factors Y and Z

(d) factor X only

  1. miRNAs, tRNAs, and rRNAs all.

(a) do not code for proteins.

(b) act in the nucleus.

(c) are packaged with other proteins to form RISC.

(d) form base pairs with mRNA molecules.

  1. Which of the following statements about pseudogenes is false?

(a) Pseudogenes code for microRNAs.

(b) Pseudogenes share significant nucleotide similarity with functional genes.

(c) Pseudogenes are no longer expressed in the cell.

(d) There are estimated to be approximately 20,000 pseudogenes in the human

genome.

  1. Which of the following statements about homologous genes is true?

(a) For protein-coding genes, homologous genes will show more similarity in

their amino acid sequences than in their nucleotide sequences.

(b) Fewer than 1% of human genes have homologs in the nematode and the fruit fly.

(c) Most homologous genes arose by gene duplication.

(d) A gene in humans that has homologs in plants and prokaryotes will show the

same level of similarity in nucleotide sequence when the human and prokaryotic

sequences are compared as when the human and chimpanzee sequences are

compared.

  1. Which of the following statements about the human genome is false?

(a) About 50% of the human genome is made up of mobile genetic elements.

(b) More of the human genome comprises intron sequences than exon sequences.

(c) About 1.5% of the human genome codes for exons.

(d) Only the exons are conserved between the genomes of humans and other

mammals.

  1. You have a piece of circular DNA that can be cut by the restriction nucleases

XhoI and SmaI, as indicated in the figure below.

If you were to cut this circular piece of DNA with both XhoI and SmaI, how many

fragments of DNA would you end up with?

(a) 1

(b) 2

(c) 3

(d) 4

  1. A double-‐stranded DNA molecule can be separated into single strands by

heating it to 90°C because.

(a) heat disrupts the hydrogen bonds holding the sugar–phosphate backbone together.

(b) DNA is negatively charged.

(c) heat disrupts hydrogen-bonding between complementary nucleotides.

(d) DNA is positively charged.

  1. Your friend works at the Centers for Disease Control and Prevention and has

discovered a brand-‐new virus that has recently been introduced into the human

population. She has just developed a new assay that allows her to detect the virus

by using PCR products made from the blood of infected patients. The assay uses

primers in the PCR assay that hybridize to sequences in the viral genome.

Your friend is distraught because of the result she obtained (see Figure below)

when she looked at PCR products made using the blood of three patients suffering

from the viral disease, using her own blood, and using a leaf from her petunia

plant.

You advise your friend not to panic, as you believe she is missing an important

control. Which one of the choices listed below is the best control for clarifying the

results of her assay? Explain your answer.

(a) a PCR assay using blood from a patient who is newly infected but does

not yet show symptoms

(b) a PCR assay using blood from a dog

(c) a PCR assay using blood from an uninfected person

(d) repeating the experiments she has already done with a new tube of polymerase

  1. Why are dideoxyribonucleoside triphosphates used during DNA sequencing?

(a) They cannot be incorporated into DNA by DNA polymerase.

(b) They are incorporated into DNA particularly well by DNA polymerases from

thermophilic bacteria.

(c) Incorporation of a dideoxyribonucleoside triphosphate leads to the termination

of replication for that strand.

(d) Dideoxyribonucleoside triphosphates are more stable than deoxyribonucleoside

triphosphates.

  1. Which type of lipids are the most abundant in the plasma membrane?

(a) phospholipids

(b) glycolipids

(c) sterols

(d) triacylglycerides

  1. Where does most new membrane synthesis take place in a eukaryotic cell?

(a) at the Golgi apparatus

(b) at the endoplasmic reticulum

(c) at the plasma membrane

(d) in the mitochondria

(e) on ribosomes

  1. Consider the apical location of a particular protein expressed in gut epithelial

cells, illustrated in the figure below. Which type of defect described below is the

most likely to cause the redistribution of that protein around the entire cell,

shown in the figure below?

(a) a nonfunctional protein glycosylase

(b) the deletion of a junctional protein

(c) the truncation of a protein found in the extracellular matrix

(d) a nonfunctional flippase

  1. Which of the following statements about tumor suppressor genes is false?

(a) Gene amplification of a tumor suppressor gene is less dangerous than gene

amplification of a proto-oncogene.

(b) Cells with one functional copy of a tumor suppressor gene will usually

proliferate faster than normal cells.

(c) Inactivation of tumor suppressor genes leads to enhanced cell survival and

proliferation.

(d) Individuals with only one functional copy of a tumor suppressor gene are

more prone to cancer than individuals with two functional copies of a

tumor suppressor gene.

  1. A metastasis is.

(a) a secondary tumor in a different part of the body that arises from a cell

from the primary tumor.

(b) a cell that is dividing in defiance of normal constraints.

(c) a part of the primary tumor that has invaded the surrounding tissue.

(d) the portion of the cancerous tumor that displays genetic instability.

  1. The artificial introduction of three key into an adult cell can convert the

adult cell into a cell with the properties of ES cells.

(a) chromosomes

(b) viruses

(c) hormones

(d) transcription factors

  1. An individual that arises by reproductive cloning has a nuclear genome that is identical

to

.

(a) the female who donated the egg.

(b) the adult who donated the cell for nuclear transplantation.

(c) both the female who donated the egg and the adult who donated the

cell for nuclear transplantation.

(d) the foster mother in which the embryo is placed.

  1. How do reproductive cloning and therapeutic cloning differ?

(a) The DNA in the nucleus of cells produced for therapeutic cloning is

genetically identical to the donor genome, whereas in cells produced for

reproductive cloning it is not.

(b) Reproductive cloning requires a supply of fertilized donor egg cells,

whereas therapeutic cloning requires unfertilized egg cells.

(c) Therapeutic cloning requires nuclear transplantation, whereas reproductive

cloning does not.

(d) Embryos are placed into foster mothers during reproductive cloning but not

during therapeutic cloning.

  1. A pluripotent cell.

(a) can only be produced in the laboratory.

(b) can give rise to all the tissues and cell types in the body.

(c) can only give rise to stem cells.

(d) is considered to be terminally differentiated.

  1. When a terminally differentiated cell in an adult body dies, it can typically be replaced

in the body by a stock of.

(a) proliferating precursor cells.

(b) cells more apically located than the terminally differentiated cells.

(c) Wnt proteins.

(d) induced pluripotent cells.

  1. Which type of junction contributes the most to the polarization of epithelial cells?

(a) adherens junctions

(b) desmosomes

(c) tight junctions

(d) gap junctions

  1. Tight junctions.

(a) allow small, water-soluble molecules to pass from cell to cell.

(b) interact with the intermediate filaments inside the cell.

(c) are formed from claudins and occludins.

(d) are found in cells in connective tissues.

  1. In step 4 of glycolysis, a six-carbon sugar (fructose 1,6-bisphosphate) is cleaved

to produce two three-carbon molecules (dihydroxyacetone phosphate and

glyceraldehyde 3-phosphate). Which enzyme catalyzes this reaction?

(a) aldolase

(b) phosphoglucose isomerase

(c) enolase

(d) triose phosphate isomerase

  1. Pyruvate can be converted into many other molecules by various biosynthetic

and metabolic pathways, which makes it a central hub in the regulation of

cellular metabolism. Which of the following molecules is not made from

pyruvate?

(a) oxaloacetate

(b) ethanol

(c) lactate

(d) NADH

  1. Because bacteria do not have mitochondria, they cannot produce ATP in a

membrane-dependent fashion.

A. True

B. False

  1. After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you

purify the RNAs attached to it. Which of the following proteins do you expect the

RNA from the rough endoplasmic reticulum to encode?

(a) soluble secreted proteins

(b) ER membrane proteins

(c) plasma membrane proteins

(d) all of the above

  1. Cells have oligosaccharides displayed on their cell surface that are important for cell–

cell recognition. Your friend discovered a transmembrane glycoprotein, GP1, on a

pathogenic yeast cell that is recognized by human immune cells. He decides to purify

large amounts of GP1 by expressing it in bacteria. To his purified protein he then adds

a branched 14-sugar oligosaccharide to the asparagine of the only Asn-X-Ser sequence

found on GP1 (Figure Q15-48). Unfortunately, immune cells do not seem to recognize

this synthesized glycoprotein. Which of the following statements is a likely

explanation for this problem?

Figure Q15-48

(a) The oligosaccharide should have been added to the serine instead of the

asparagine.

(b) The oligosaccharide should have been added one sugar at a time.

(c) The oligosaccharide needs to be further modified before it is mature.

(d) The oligosaccharide needs a disulfide bond.

  1. Which of the following statements about secretion is true?

(a) The membrane of a secretory vesicle will fuse with the plasma membrane

when it discharges its contents to the cell’s exterior.

(b) Vesicles for regulated exocytosis will not bud off the trans Golgi