Multiple choice. Choose the best answer (2 points each)1.___B__ The light reactions of photosynthesis supply the Calvin cycle with:
A) H2OB and NADPH. B) ATP and NADPH. C) sugar and O2. D) light energy. E) CO2 and ATP.
2 __B___ If carbon dioxide with a radioactive tag on its oxygen atom were given to an actively photosynthesizing plant, in which of the following molecules would you expect the radioactive oxygen to finally appear? a) carbon dioxide; b) glucose; c) molecular (atmospheric) oxygen; d) water.
3.___B__ During photosynthesis, NADP is reduced by electrons coming directly from:
a) water; b) photosystem I; c) photosystem II; d) carbon dioxide.
4.____B_ If the Calvin cycle used all of the PGAL it produced to make glucose: a) photosynthesis would be much more efficient; b) the Calvin cycle would stop; c) the production of ATP by photophosphorylation would stop; d) the production of ATP by photophosphorylation would increase.
5.___D__ Which of the following processes is most directly driven by light energy?
A) ATP synthesis B) creation of a pH gradient by pumping protons across the thylakoid membrane
C) reduction of NADP D) removal of electrons from chlorophyll reactive center molecules
E) carbon fixation in the stroma
6.___C__ Which of the following does not occur during the Calvin cycle?
A) oxidation of NADPH B) carbon fixation C) release of oxygen D) regeneration of the CO2 acceptor RUBP E) consumption of ATP
7.____C_ In the thylakoid membranes, what is the main role of the antenna pigment molecules?
A)transfer electrons to electron transport chain and then NADPH B)split water and release oxygen to the reaction-center chlorophyll C)harvest photons and transfer light energy to the reactive-center chlorophyll D)synthesize ATP from ADP and Pi E)concentrate photons within the stroma
8.__D___ All of the events listed below occur in the light reactions of photosynthesis except
A) ADP is phosphorylated to yield ATP. B) NADP+ is reduced to NADPH. C) oxygen is produced.
D )carbon dioxide is incorporated into PGA. E )light is absorbed and funneled to reactive-center chlorophyll a.
9.___E__ Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be:
A) to do experiments to generate an action spectrum. B) to test for CO2 fixation in the dark.
C) to determine if they have thylakoids in the chloroplasts. D) to test for production of either sucrose or starch. E) to test for liberation of O2 in the light.
10.___D__ One carbon dioxide molecule reacts in each "turn" of the Calvin cycle. How many turns of the cycle are required for the synthesis of one glucose molecule? A) 1 B) 2 C) 3 D) 6 E) 12
11.___C__ Do photosynthesizing plant cells contain mitochondria? a) No, they have chloroplasts to produce the ATP needed to power various cell activities; b) Yes, because they must convert glucose into starch; c) Yes, so they can harvest the energy that was stored in glucose during photosynthesis;
d) Yes, mitochondria contain the enzymes needed for glycolysis; e) No, plants use the Calvin cycle rather than the Krebs cycle to generate energy.
12.___B__ While on a field trip to the tropical rain forest, you discover a plant with orange leaves. It contains a photosynthetic pigment called orangophyll. Tests show that orangophyll absorbs purple, blue, and green light most strongly, and it reflects orange, red, and yellow light. You plan to grow these plants and sell them. What wavelengths of light should your grow-tubes supply for best growth?
a) Orange, red, and yellow light because the color of the leaves indicates the best wavelengths;
b) Purple, blue, and green light because orangophyll absorbs those wavelengths; c) Red and blue light because those are the best wavelengths for photosynthesis; d) Orange, red, and yellow light because orangophyll reflects those wavelengths; e) Purple, blue, and green light because orangophyll reflects those wavelengths.
13.__B___ The two photosystems of photosynthesis are connected by : a) chlorophyll molecules; b) an electron transport chain; c) NADP molecules; d) dark reactions; e) the stroma
14.___C__In molecular biology, what is significant about the year 1953? a) the human genome project was completed b) the process of transformation was discovered c) Watson and Crick published the “Double Helix” paper of DNA structure d) Rosalind Franklin was born e) proteins were discovered.
15.__A___Griffith’s experiments with rough and smooth forms of Streptococcus pneumonia demonstrated: a) that transformation can occur b) semiconservative DNA replication c) DNA was the genetic material d) that bacteriophage can infect bacteria e) the importance of x-ray diffraction as a research tool.
16.___D__The last sentence in Watson and Crick’s paper about the structure of DNA commented: a) on the complementary base pairing of the nucleotides A and T b) about how genotype determines phenotype c) that Franklin had stolen some of their valuable data d)that the structure they proposed suggested a possible mechanism of DNA replication
17.__C___ What kind of chemical bond is found between paired bases of the DNA double helix?
A) sulfhydryl B) ionic C) hydrogen D) phosphate E) covalent
18.___C__ Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA. Who did this experiment?
A) Frederick Griffith B) Alfred Hershey and Martha Chase C) Oswald Avery, Maclyn McCarty, and Colin MacLeod D) Erwin Chargaff E) Matthew Meselson and Franklin Stahl
19.__A___ For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?
A) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
B) Meselson and Stahl already did this experiment.
C) Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.
D) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long.
E) There is no isotope of nitrogen.
20.__E___Which of these mechanisms ensures that the DNA sequence in the genome remains accurate?
A)proofreading during DNA replication B)excision repair C)mismatch repair D)complementary base pairing during DNA replication E)all of the above
21._D____Individuals with the disorder xeroderma pigmentosum must avoid exposure to sunlight because their cells have an impaired ability to: A) exchange DNA with other cells. B) undergo mitosis.
C) recombine homologous chromosomes during meiosis. D)r epair thymine dimers. E) replicate DNA.
22.__A__Which one of the following accurately reflects complementary base-pairing in the
DNA molecule? a) Guanine-cytosine; b)Guanine-adenine; c) Cytosine-hemanine; d) Uracil-thymine; e) Adenine-cytosine
23.__E___ DNA replication is said to be semiconservative. This means that: a) half of the old strand is degraded and half is used as a template for the replication of a new strand; b) one of the two resulting double helices is made of 2 old strands and the other is made of 2 new strands; c) the old double helix is degraded and half of its nucleotides are used in the construction of two new double helices; d) one strand of the new double helix is made of DNA and the other strand is made of RNA; e) each new double helix consists of 1 old and 1 new strand.
24.__C___The flow of genetic information in this “organism” is an exception to the “Central Dogma”:
a) E.coli b) bacteria c) retrovirus d) fire fly e)cow
25.__C___ The observation that there are 20 different amino acids but 64 possible different codons is explained by the fact that the genetic code is: a) nonoverlapping; b) universal; c) redundant ; d) a triplet code.
26.___B__This term describes the condition that every cell in an organism’s body has all of the genes to make an entire organism: a) promoter b) totipotent c) gene expression d) Central Dogma e) wobble
27._C___ How does RNA polymerase know where to start transcribing a gene into mRNA?
a) It always starts at one end of the chromosome; b) Transfer RNA acts to translate the message to RNA polymerase; c) It starts at a certain nucleotide sequence called a promoter; d) The ribosome directs it to the correct portion of the DNA molecule; e) It looks for the AUG start codon.
28.__C___ The anticodon of a particular tRNA molecule is: A) complementary to the corresponding triplet in rRNA. B) catalytic, making the tRNA a ribozyme. C) complementary to the corresponding mRNA codon. D) the part of tRNA that bonds to a specific amino acid.
29.__C___Which component is not directly involved in translation?
A) GTP B) mRNA C) DNA D) ribosomes E) tRNA
29.__E___A particular eukaryotic protein is 300 amino acids long. Which of the following could be the maximum number of nucleotides in the DNA that codes for the amino acids in this protein?
A)300 B) 3 C) 1,800 D) 100 E) 900
30.__B___If the triplet CCC codes for the amino acid proline in bacteria, then in plants CCC should code for A) valine. B) proline. C) cystine. D) leucine. E) phenylalanine.
31.__D___Which of the following is not a part of the eukaryotic transcription initiation complex?
A) promoter B) RNA polymerase C) TATA box D) an amino acid E) transcription factors
32.___B__All of the following are directly involved in translation except :
A) ribosomes. B) DNA. C) tRNA. D) aminoacyl-tRNA synthetase enzymes. E) mRNA.
33.___D__A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is : A) UUA. B) TTT. C) UUU. D) AAA. E) either UAA or TAA, depending on first base wobble.
34.__A___ A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of a phenylalanine. The consequence of this for the cell will be that
A) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
B) none of the proteins in the cell will contain phenylalanine.
C)t he cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons.
D) the ribosome will skip a codon every time a UUU is encountered.
E )None of the above will occur; the cell will recognize the error and destroy the tRNA.
35.__A___What are ribosomes composed of? A)both rRNA and protein B) rRNA only C) mRNA, tRNA, rRNA, and protein D) proteins only E) mRNA, rRNA, and protein
36.___A___ The genetic information is expressed as the phenotype when : a) a sequence of amino acids is put together into a polypeptide; b) new DNA is made using the old strand as a template; c) gametes come together in fertilization; d) mRNA is made; e) a hormone is sent from the nucleus to the cytoplasm.
37.__A___From the following list, which is the first event in translation in eukaryotes?
A) base pairing of activated methionine-tRNA to AUG of the messenger RNA
B) binding of the larger ribosomal subunit to smaller ribosomal subunits
C) elongation of the polypeptide
D) covalent bonding between the first two amino acids
E) Both B and D occur simultaneously.
38.___C__ At one point as a cell carried out its day-to-day activities, the nucleotides GAT were paired with the nucleotides CUA. This pairing occurred: a) in a double-stranded DNA molecule; b) during translation; c) during transcription; d) when an mRNA codon paired with a tRNA anticodon; e) It is impossible to say, given this information.
39. (8 points) What are the three products produced by the light dependent reactions of photosynthesis? Describe the events that occur in photosystems I and II that result in the formation of these products. Could an autotrophic organism survive if it only had photosystem I? Explain.
The three products produced are ATP, NADPH and O2. When light strikes the reactive center of PS I, electrons are excited, grabbed by an electron acceptor, and passed to the ets, which contributes to the H+ gradient that allows ATP to be made by photophosphorylation. Water is also split and the electrons from water replace those lost form the reactive center of PSI. H+ released from water contributes to the H+ gradient that allows ATP to be made by photophosphorylation and the oxygen atoms from water splitting combine to form O2. When light strikes the reactive center of PS II, electrons are excited, grabbed by an electron acceptor, and passed to NADP. The reduction of NADP require snot only electrons from PS I, but protons. These come from the dissociation of water in the stroma. The removal of the H+ ions contributes to the H+ gradient that allows ATP to be made by photophosphorylation . Electrons lost from PSI are replaced by electrons from PS II (coming via the ets).
Organisms cannot survive without PS I. No reductant (NADP) can be made so the Calvin cycle would not operate.
40. (8 points) Watson and Crick's model of DNA structure suggested a template mechanism for DNA replication. Explain how Messelson and Stahl used bacteria, heavy nitrogen and ultracentrifugation to demonstrate that DNA replication was semiconservative as opposed to being conservative or dispersive.
Messelson and Stahl grew E. coli bacteria in broth containing N-15 nucleotides and then moved the cells into new broth containing N-14 nucleotides and let them grow for a) one generation and b) two generations. In each of these experiments, they removed the cells from the N-14 media, lysed them, isolated the DNA, and separated the DNA by centrifugation. In the centrifuge tube, N14 DNA was the lightest, N14/15 hybrid DNA was in the middle of the tube, and N-15 DNA was the heaviest. Analysis of the data after one round of replication showed N-14/N15 hybrids which ruled out conservative replication. Analysis of the data after two rounds of replication showed N-14/N15 hybrids and N14 DNA. This ruled out dispersive replication but was consistent with semi-conservative replication.
41. (8 points) What is the role of t-RNA in translation? Describe the structure of t-RNA and explain how this structure is related to its function. What is wobble? What is a possible advantage of wobble?
The role of t-rna is translate the language of genes (nucleotides language) into the language of proteins (amino acids). It “reads” the codon in an m-rna (by paring its anticodon with the m-rna codon) and places the appropriate amino acid into the growing polypeptide chain. Although it is a single-stranded rna molecule, it folds into a complex 3-D shape. At its 3’ end is the amino acid attachment site. The anticodon loop contains the anticodon that binds with the codon of the m-rna. Wobble refers to the fact that base pairing between the t-rna anticodon and the m-rna codon can be ‘sloppy” in the third nucleotide of the codon. Thus, the same t-rna may bind with two different codons. This explains why there are less than 61 types of t-rna (actually there are 45).
Quick Reply
