Cell Biology
Midterm Exam
Course Introduction
Cell Biology explores the structure, function, and processes of cells, which are the basic units of life. This course covers topics such as cell organelles, membrane structure and transport, cell communication, cell cycle, and energy conversion. Students will learn about the molecular mechanisms underlying cell growth, division, differentiation, and cell death, as well as advanced topics such as cellular signaling pathways and the role of cells in development and disease. The course combines theoretical knowledge with laboratory techniques to provide a comprehensive understanding of cellular systems and their significance in biological research and medicine.
Recommended Textbook Principles of Biochemistry 5th Edition by Moran Horton
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Page 2
Chapter 1: Introduction to Biochemistry
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Q1) The mitotic spindles are formed from microtubule proteins.
A)True
B)False
Answer: True
Q2) The conformation of a protein enzyme determines whether it is functional or not.
A)True
B)False
Answer: True
Q3) Enzymes are protein catalysts that form an intermediate with a substrate that fits into it.
A)True
B)False
Answer: True
Q4) Which linkage(s)occur extensively in nucleotides?
A)Amide.
B)Phosphoanhydride.
C)Phosphate ester.
D)Ether.
E)Both B and C above.
Answer: E
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Chapter 2: Water
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Q1) Which is true about the solubility of electrolytes in water?
A)They are all insoluble in water.
B)They are usually only sparingly soluble in water.
C)They often form super-saturated aqueous solutions.
D)They readily dissolve and ionize in water.
Answer: D
Q2) Blood pH is primarily regulated by
A)a protein buffer system.
B)the carbon dioxide - carbonic acid - bicarbonate buffer system.
C)the phosphate buffering system.
D)carbonic acid (H CO ).
E)B and C.
Answer: B
Q3) Attractions of oppositely charged functional groups of proteins are sometimes called ________.
A)salt bridges or ion pairing
B)disulfide bridges
C)London bridges
D)hydrophilic bridges
Answer: A
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Chapter 3: Amino Acids and the Primary Structures of Proteins
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Q1) Most proteins contain an approximately equal amount of each of the standard amino acids.
A)True
B)False
Answer: False
Q2) Basic amino acids are ________ (positive,negative)at pH 7 and acidic R group amino acids are ________ (positive,negative)at pH 7.
A)negative;positive
B)negative;negative
C)positive;negative
D)positive;positive
Answer: C
Q3) The RS system of nomenclature describes
A)the relative sizes of molecules.
B)the way the amino acid side chains are arranged.
C)the absolute configuration about chiral carbon centers .
D)the strength of the chemical groups in amino acids.
Answer: C
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Chapter 4: Proteins: Three-Dimensional Structure and Function
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Q1) The trans configuration of most peptide groups is adopted in cells because it
A)is the only one available.
B)minimizes steric hindrance of R groups.
C)is favored in protein synthesis.
D)Both B and C.
E)All of the above.
Q2) All proteins possess primary,secondary,tertiary and quaternary structure.
A)True
B)False
Q3) Which technique is commonly used to determine the three-dimensional conformation of a protein?
A)Isoelectric focusing.
B)The Edman degradation.
C)SDS-PAGE.
D)X-ray crystallography.
Q4) Proline exists in the cis configuration more frequently than any other amino acid.
A)True
B)False
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Chapter 5: Properties of Enzymes
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Sample Questions
Q1) L-Glutamate + ATP + NH + L-glutamine + ADP + Pi
A)oxidoreductase
B)lyase
C)isomerase
D)transferase
E)hydrolase
F)ligase
Q2) An enzyme is irreversibly inhibited by diisopropylfluorophosphate (DFP).What does this show?
A)The enzyme has been denatured by DFP.
B)Serine is likely an important residue in the active site.
C)DFP is an allosteric modulator of the enzyme.
D)DFP is an analog of the enzyme's substrate.
Q3) It is difficult to determine either Km or Vmax from a graph of velocity vs.substrate concentration because
A)too much substrate is required to determine them.
B)the graph is sigmoidal.
C)an asymptotic value must be determined from the graph.
D)the points on the graph are often not spread out on the hyperbola.
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Page 7
Chapter 6: Mechanisms of Enzymes
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Q1) A histidine was determined to be the critical residue involved in an enzyme-catalyzed reaction.If the pKa of the histidine is known to be 6.5 in the active site and the pH of maximum catalytic activity is 7.2,what is likely the primary role of histidine in the catalytic reaction?
A)Acts as a proton donor or acceptor.
B)Forms a covalent bond with the substrate.
C)Stabilizes a charged intermediate.
D)Reduces the entropy of the substrate.
Q2) If a plot of enzyme activity versus pH is sigmoidal then acid-base catalysis can be ruled out as a mode of catalysis.
A)True
B)False
Q3) The relative orientation of colliding molecules only affects reactions rates when the energy during impact is low.If the energy of impact is high enough,orientation is unimportant.
A)True
B)False
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8
Chapter 7: Coenzymes and Vitamins
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Q1) Unlike coenzymes that are prosthetic groups,________ are altered in the course of an enzyme reaction and dissociate from the active site.
A)isozymes
B)cosubstrates
C)metalloenzymes
D)holoenzymes
Q2) Metal-activated enzymes may require a metal ion or simply be stimulated in the presence of the ion.
A)True
B)False
Q3) Lack of thiamine (vitamin B1)leads to the disease beriberi.
A)True
B)False
Q4) What is another name for vitamin B12?
A)Thiamine.
B)Tetrahydrofolate.
C)Cobalamin.
D)Biotin.
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Chapter 8: Carbohydrates
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Sample Questions
Q1) Most of the carbohydrates on earth are produced by photosynthesis in plants.
A)True
B)False
Q2) Sugar alcohols do not have a carbonyl group.
A)True
B)False
Q3) Some glycoproteins may have identical protein components and variable polysaccharide components.
A)True
B)False
Q4) lipo-oligosaccharides that bacteria infecting legume plants produce
A)nodulation factor
B)H antigen (blood groups)
C)hyaluronic acid
D)aggrecan
E)bacterial cell wall (peptidoglycan)
Q5) Furanoses have more three-dimensional conformations than pyranoses.
A)True
B)False
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Chapter 9: Lipids and Membranes
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Sample Questions
Q1) thin layer chromatography
A)separate fatty acid esters
B)separate neutral lipids and phospholipids
C)separate groups of neutral lipids
D)lateral movement of proteins in cell membranes
E)diacylglycerol separation based on chain length and degree of unsaturation
Q2) Triglycerols containing only saturated long chain fatty acids tend to remain ________ at room temperature.
A)unsaturated
B)liquid
C)solid
D)oils
Q3) In the adenyl cyclase signaling pathway the second messenger(s)is(are)________.
A)ATP and GTP
B)protein kinase A
C)cyclic AMP or cyclic GMP
D)AMP
Q4) All sphingolipids are derivatives of ceramide.
A)True
B)False
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Chapter 10: Introduction to Metabolism
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Q1) Which thermodynamic quantity is used to determine if a reaction in a cell is spontaneous?
A) G°'
B) G
C) H
D) S
Q2) For a step in a reaction pathway to serve as a control point it should be ________.
A)irreversible
B)endergonic
C)far from equilibrium
D)Both A and C
E)All of the above
Q3) Enzymes that oxidize NADH can best be measured by the ________ .
A)increase in absorbance at 340 nm
B)decrease in absorbance at 340 nm
C)increase in absorbance at 250 nm
D)decrease in absorbance at 250 nm
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12
Chapter 11: Glycolysis
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Q1) Two molecules of ATP are produced per glucose during the hexose stage of glycolysis.
A)True
B)False
Q2) Two molecules of ATP are consumed per glucose during the triose stage of glycolysis.
A)True B)False
Q3) Two molecules of ATP are consumed per glucose molecule during the hexose stage of glycolysis.
A)True
B)False
Q4) The slowing of glycolysis in the presence of oxygen is called the ________ effect.
A)Bohr
B)Michaelis-Menton
C)Pasteur
D)Pauling
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Page 13
Chapter 12: Gluconeogenesis, the Pentose Phosphate
Pathway, and Glycogen Metabolism
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Q1) Phosphorylation can be used to either inactivate or activate enzymes.This is a key element in the regulation of glucose metabolism.Phosphorylation of glycogen phosphorylase ________ it;phosphorylation of glycogen synthase ________ it.
A)activates;activates
B)activates;inactivates
C)inactivates;inactivates
D)inactivates;activates
Q2) The major regulatory step of the pentose phosphate pathway is catalyzed by which enzyme?
A)Transaldolase.
B)Phosphofructokinase-1.
C)Glucose 6-phosphate dehydrogenase.
D)Ribose 5-phosphate isomerase.
Q3) What is the driving force for the reaction catalyzed by UDP-glucose pyrophosphorylase that converts glucose 1-phosphate to UDP-glucose?
A)Its large negative free energy change.
B)The formation of an energy-rich product.
C)The subsequent hydrolysis of pyrophosphate.
D)The change in concentration of UTP.
Page 14
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Chapter 13: The Citric Acid Cycle
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Q1) The citric acid cycle oxidizes pyruvate,and some of the pathway intermediates are starting materials for many biosynthetic pathways.This means that the citric acid cycle is ________.
A)amplifying
B)catabolic
C)anabolic
D)amphibolic
Q2) Which of the following enzymatic reactions are examples of substrate level phosphorylation?
A)Succinyl Co-A synthetase.
B)Pyruvate kinase.
C)Phosphoglycerate kinase.
D)All of the above.
Q3) Pyruvate passes through the outer mitochondrial membrane by ________.
A)porin proteins
B)passive transport
C)pyruvate translocase
D)simple diffusion through the lipid bilayer
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15
Chapter 14: Electron Transport and Atp Synthesis
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Q1) Complex II participates in both the electron transport chain and the citric acid cycle.
A)True
B)False
Q2) White blood cells in mammals can produce toxic superoxide ions to kill bacterial cells.
A)True
B)False
Q3) The chemiosmotic theory is a concept that ________.
A)the transport of Na+ and K+ across cell membranes is by active transport
B)explains how transport by facilitated diffusion reaches a saturation limit
C)explains the blood-brain barrier
D)a proton gradient drives the formation of ATP
Q4) How many protons are translocated across the inner mitochondrial membrane by complex III for each pair of electrons passing through the electron transport chain? A)0
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Chapter 15: Photosynthesis
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Q1) Which enzyme is not part of the Calvin cycle?
A)Triose phosphate isomerase.
B)Rubisco.
C)Plastocyanin.
D)Transketolase.
Q2) What is wavelength of light if the energy of one photon is 2.925 × 10-¹ J?(h = 6.63 × 10-³ J s and c = 3.00 × 10 m s-¹)
A)680nm
B)700 nm
C)5.8 m
D)1.5 × 10-³ nm
Q3) Bacteria with PS I use sunlight to produce NADPH while those with PSII do not.
A)True
B)False
Q4) Which molecule is the CO<sub>2</sub> acceptor in the first step of the Calvin cycle?
A)Rubisco.
B)Ribulose 1,5-bisphosphate.
C)3-phosphoglycerate.
D)Glyceraldehyde-3-phosphate.
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Chapter 16: Lipid Metabolism
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Q1) Linoleate is required for human diet because it is necessary for the synthesis of arachidonate and eicosanoids.
A)True
B)False
Q2) Which of the following is mismatched?
A)Bile salts - intestinal absorption of lipids.
B)B-estradiol - sex characteristics.
C)Cholesterol - membrane fluidity.
D)Squalene - lipid vitamin.
Q3) The reaction,Palmitoyl-ACP Palmitate + HS-ACP proceeds via which of the following enzymes?
A)Thioesterase.
B)Ketoacyl-ACP synthase.
C)Transacylase.
D)None of the above.
Q4) In eukaryotes the enzyme complex called fatty acid synthase is responsible for the assembly of the fatty acid chain.
A)True
B)False
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Chapter 17: Amino Acid Metabolism
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Q1) Which of the following is/are true concerning transanimation reactions?
A)They can convert -keto acids to -amino acids.
B)All require the coenzyme pyridoxal phosphate.
C)The catalyzed reactions are near-equilibrium.
D)All of the above.
Q2) The carbon in urea originates from ________.
A)aspartate
B)ornithine
C)bicarbonate
D)ATP
Q3) In the urea cycle which molecule is transported from the mitochondrial matrix to the cytosol as ornithine is transported in the opposite direction?
A)Arginine.
B)Citrulline.
C)Glutamate.
D)Carnitine.
Q4) The disease alcaptonuria is caused by a defect in the kidney transport of cysteine.
A)True
B)False
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Chapter 18: Nucleotide Metabolism
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Q1) Purines and pyrimidines formed during digestion of food are more likely to be salvaged than those formed inside the cell.
A)True
B)False
Q2) In the reactions catalyzed by xanthine oxidase,electrons are transferred to ________ to form ________.
A)O<sub>2</sub>;H<sub>2</sub>O<sub>2</sub>
B)H O<sub>2</sub>;O<sub>2</sub>
C)H O;O<sub>2</sub>
D)O<sub>2</sub>;H O
Q3) When a purine or a purine triphosphate is bound to the specificity site of ribonucleotide reductase,the activity of the catalytic site of the enzyme is specific for a pyrimidine or a pyrimidine triphosphate.
A)True
B)False
Q4) The pathway for the synthesis of IMP releases considerable energy and is an important source of ATP.
A)True
B)False
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Chapter 19: Nucleic Acids
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Q1) The packaging of DNA in cells results in about a ________-fold reduction in length compared to the fully extended DNA (fully stretched out).
A)10
B)700
C)8000
D)200,000
Q2) Bacteria produce many restriction endonucleases.What prevents these enzymes from degrading the host DNA?
A)A bacterium will produce endonucleases that recognize sequences that are not present in its own DNA.
B)The strong association between the histones and bacterial DNA prevent the endonucleases from acting on them.
C)The endonucleases are transported out of the cell so quickly they cannot significantly affect the host DNA.
D)The host DNA is specifically methylated and is therefore protected from cleavage.
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21
Chapter 20: DNA Replication, repair, and Recombination
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Q1) The incorporation of new nucleotides into a growing strand of DNA occurs during
A)the elongation stage
B)nucleation
C)initiation
D)assembly of the protein machine
Q2) Which molecules have repair mechanisms in most cells?
A)DNA.
B)RNA.
C)Proteins.
D)DNA and proteins.
E)DNA,RNA and proteins.
Q3) Although histones and DNA are made in the same parts of the eukaryotic cell,the packaging of them in the nucleosome slows down replication so that it is slower than that of prokaryotes.
A)True
B)False
Q4) DNA polymerase III is the largest DNA polymerase in E.coli.
A)True
B)False
Page 22
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Chapter 21: Transcription and RNA Processing
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Q1) The product of the lacZ gene is ________.
A)lac repressor
B) -galactosidase
C)thiogalactoside transacetylase
D)lactose permease
Q2) The template strand of DNA is copied by RNA polymerase from
A)both 3' 5' and 5' 3' ends.
B)5-10 nucleotides before the +1 transition site.
C)3' 5' end.
D)5' 3' end.
Q3) TATA binding protein is the only transcription factor common among all eukaryotic RNA polymerases.
A)True
B)False
Q4) RNA polymerase has a higher error rate (one mutation for every 1 million nucleotides incorporated)than DNA polymerase because RNA polymerase does not have exonuclease proofreading activity but DNA polymerase does.
A)True
B)False
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Chapter 22: Protein Synthesis
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Q1) Which statement is false concerning aminoacyl-tRNA synthetase?
A)It recognizes only one amino acid,but may recognize more than one tRNA.
B)It requires a conversion from ATP to ADP.
C)Hydrolysis of pyrophosphate essentially makes its reaction irreversible.
D)Some synthetases bind the anticodon and others do not.
Q2) EF-Ts promotes the dissociation of GDP from the EF-Tu-GDP complex to recycle this elongation factor.
A)True
B)False
Q3) Termination (stop)codons are recognized by specific proteins that cause newly synthesized peptides to be released from the ribosome.
A)True
B)False
Q4) The acceptor stem of tRNA consists of the ________.
A)loop that includes the anticodon
B)terminal CCA only
C)5' end and a region near the end 3' end that are base-paired to each other
D)variable arm and the D arm
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