According to the fluid-mosaic model of cell membranes, which of the following is TRUE regarding membrane phospholipids.. Which of the following hormones that we discussed in class initia
Trang 1BIOLOGY 1A MIDTERM # 1 September 28th, 2011
1 Sit every other seat and sit by section number Place all books and paper on the floor Turn off all phones, pagers, etc and place them in your backpack They cannot be visible No calculator is permitted
Scantron Instructions
2 Use a #2 pencil ERASE ALL MISTAKES COMPLETELY AND CLEARLY
3 Write in & bubble in your name, SID, and section # (last 2 digits) The top 8 boxes of the ID field are for your SID, the bottom two are for the last 2 digits of your section # Put your name on the scantron form Under “test” write in your GSI’s name See below
EXAM Instructions:
4 Print your name on THIS COVER SHEET (otherwise, you will get a ZERO)
5 Leave your exam face up When told to begin, check your exam to see that there are 8 numbered pages, 50 multiple-choice questions The exam is worth 100 pts Each question is worth 2 points unless otherwise indicated You are NOT PENALIZED for guessing!
6 Read all questions & choices carefully before bubbling in your response
7 Do not talk during the exam The exam is closed book You cannot use a calculator If you have a question, raise your hand; a GSI will help you They will not give you the answer nor can they explain scientific terms (e.g binding affinity, etc.)
8 LOCATE YOUR GSI Turn in your SCANTRON and EXAM to your GSI YOU MUST TURN IN BOTH or
else you will get a ZERO
9 WHEN TOLD TO STOP- YOU MUST REALLY STOP, even if you are not finished! Bubble in guesses BEFORE THIS TIME If you continue to write after time has been called you will risk getting a 0
Trang 21 Which of the following statements is TRUE about enzyme-catalyzed reactions?
A They are always exergonic
B The equilibrium of the enzyme-catalyzed reaction favors products, whereas the equilibrium for the same reaction
in the absence of the enzyme favors reactants
C The activation energy is the same as for the un-catalyzed reaction
D The activation energy is lower than that for the un-catalyzed reaction
E The free energy change is lower for the enzyme-catalyzed reaction than it is for the same reaction in the absence
of the enzyme
2 According to the fluid-mosaic model of cell membranes, which of the following is TRUE regarding membrane phospholipids?
A They are anchored in place by intermediate filaments
B They can move laterally along the plane of the membrane
C They have hydrophilic tails in the interior of the membrane
D They occur in an uninterrupted bilayer, with membrane proteins bound only to the surface of the membrane
E They are free to leave the membrane and dissolve in the interstitial fluid
3 The transmembrane regions of a K + channel protein are likely to have amino acids with which type of R-groups exposed to the interior of the plasma membrane?
A hydrophobic
B acidic
C polar
D hydrophilic
E basic
4 Some cells use fermentation to regenerate NAD+ after glycolysis; how does fermentation regenerate NAD+?
A the fermentation process regenerates NAD+ by feeding the electrons into the oxidative phosphorylation pathway
B it regenerates NAD+ using the citric acid cycle
C it regenerates NAD+ using energy from the proton gradient in the inter-membrane compartment
D it regenerates NAD+ by removing the electrons and adding them to oxygen
E it regenerates NAD+ by transferring the electrons to an organic acceptor molecule
5 Which reaction below represents an anabolic process?
A C6H12O6 + 6O2 → 6CO2 + 6H2O
B fructose + glucose → sucrose
C protein + ATP → protein-P + ADP
D RNA → nucleotides
E GTP + H2O → GDP + Pi
6 In the process of facilitated diffusion,
A no transport protein or channel proteins are required
B solutes are transported against their concentration gradient
C solutes are moved down their concentration gradient
D transport proteins become denatured
E ATP is required
7 Which of the following statements about chlorophyll is FALSE?
A Only one form is found in succulent plants
B It is a photosynthetic pigment
C It has sufficient hydrophobicity to associate with the thylakoid membranes
D It absorbs light in the blue and red regions of the spectrum
E It is green in color
8 The light reactions of photosynthesis supply the Calvin cycle with
A H2O and NADPH
B O2 and NADP+
Trang 39 Allosteric inhibition of an enzymatic reaction
A can occur when the product of the reaction resembles an enzyme cofactor
B occurs when the inhibitor binds to the substrate binding site
C usually involves the first unique product in a pathway acting on the enzyme involved in last step of the pathway
D occurs when the inhibitor binds at a location distinct from the active site
E usually involves the first enzyme in a pathway
10 Which of the following is a FALSE statement?
A Photosynthesis produces O2; respiration produces CO2
B The principle electron carrier in respiration is NAD+; the principle electron carrier in photosynthesis is NADP+
C ATP is produced during photosynthesis but not during respiration
D Photosynthesis is powered by light energy; respiration is powered by the chemical energy of fuel molecules
E Photosynthesis consumes CO2; respiration consumes O2
11 Which of the following is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?
A The double bonds form a kink in the fatty acid tail, forcing adjacent phospholipids to be spaced further apart
B Unsaturated fatty acids have a higher cholesterol content
C Unsaturated fatty acids permit more water in the interior of the membrane
D The double bonds block interaction among the hydrophilic head groups of the lipids
E The double bonds result in a shorter fatty acid tail
12 Many signal transduction pathways utilize second messengers to
A transport a signal through the lipid bilayer of the plasma membrane
B relay a signal from the outside of the cell to the inside
C relay a signal from the inside of a cell membrane to the outside of the cell
D decrease the message once the signal molecules have left the receptor
E relay the message from the inner surface of the plasma membrane throughout the cytoplasm
13 During glycolysis,
A glucose is reduced to pyruvate
B pyruvate undergoes oxidation in the mitochondrion
C CO2 is produced
D ATP is generated during electron transport
E NAD+ is reduced
14 Which of the following hormones that we discussed in class initiates biological reactions by crossing the plasma membrane and then binding to a receptor?
A Estradiol
B Glucagon
C Epinephrine
D Adrenalin
E Insulin
15 An enzyme that catalyzes the reaction A B changes the
A heat of reaction
B entropy of the reaction
C equilibrium concentration of A
D rate of both the forward and reverse reactions
E equilibrium constant
16 Which of the following statements regarding G proteins is FALSE?
A G proteins help relay a signal received from the cell surface to the interior of the cell
B G proteins transmit the signal directly to the nucleus
C G proteins have conserved domains (shared structure)
D G proteins act to amplify the signal creating a cascade response in the cell
E G proteins switch from an active to an inactive state by hydrolyzing GTP
Trang 417 Which of the following statements is FALSE about a chemical reaction whose equilibrium constant (K eq ) is greater than 10 4 at 37°C?
A The reaction is spontaneous
B Substrate concentration will be lower than product concentration at equilibrium
C ΔG for the reaction is positive
D ΔG for the reaction would change if the temperature were increased
E ΔG for the reaction can be calculated from the information
18 Which of the following statements is TRUE regarding cellular respiration in bacteria and eukaryotes?
A Most eukaryotes use only substrate-level phosphorylation whereas most bacteria use only oxidative
phosphorylation
B Most eukaryotes use mitochondria whereas most bacteria use their plasma membrane
C Most eukaryotes use only NAD+/NADH whereas most bacteria use only FAD+/FADH2 as their electron carriers
D Most eukaryotes do not require oxygen whereas most bacteria require oxygen
E Most eukaryotes use only glucose whereas most bacteria use only galactose
19 If a subcellular fraction from liver tissue exhibits a high level of ATP synthase activity, it most likely contains
A mitochondria
B nuclei
C lysosomes
D endoplasmic reticulum
E peroxisomes
20 A hydrogen bond between the amino acid side groups (R groups) from two different polypeptide chains in a
multi-chain protein would be considered part of the structure of the protein
A primary
B secondary
C tertiary
D quaternary
E ancillary
21 Which of the following properties is NOT a characteristic of intermediate filaments?
A They are composed of globular monomers that polymerize to form fibers
B They are protein polymers
C They provide mechanical stability to animal cells
D Their composition is tissue specific
E They include keratin filaments
22 Which of the following intercellular junctions functions to transfer molecules between animal cells?
A desmosomes
B plasmodesmata
C tight junctions
D gap junctions
E intercalated discs
23. The source of oxygen for O 2 production during photosynthesis by higher plants is
A CO2
B HCO3
C ATP
D chlorophyll
E H2O
24 In bacteria, vitamin biosynthesis decreases when tetrahydrofolate, an intermediate produced late in the biosynthetic pathway, binds to an RNA structure called a riboswitch that shuts down production of the second enzyme in the pathway This kind of regulation is best described as
A Competitive inhibition
B Noncompetitive inhibition
C Allosteric regulation
Trang 525 RNA polymerase, an enzyme responsible for transcribing DNA into RNA, contains a lysine residue that is important for binding to DNA during transcription initiation Mutations were found that converted this lysine
to either arginine , glutamate, glycine, or valine Which mutations are predicted to be the most and least harmful to the ability of the enzyme to bind DNA? The R groups are shown below
Most harmful Least harmful
A valine glutamate
B glycine arginine
C arginine glycine
D glutamate valine
E glutamate arginine
Lysine Arginine Glutamate Glycine Valine
26 A new protein kinase is found to be involved in a hormone-induced cell signaling pathway Which of the following amino acid sidechains would you expect to be the site(s) of modification in a substrate molecule that encounters the kinase?
A Sidechain I only
B Sidechain II only
C Sidechain III only
D Sidechains I and II
E Sidechains II and III
R group I R group II R group III
27 Which of the following diagrams best describes the equilibria associated with a competitive inhibitor (I)?
Trang 628 Eukaryotic cell membranes were analyzed for hormone receptors by breaking the cells open using osmotic shock, purifying the membrane fraction and incubating this sample with radiolabeled hormone ( 125 I-hormone) for five minutes A second sample of membranes was prepared and treated similarly with the addition of 125 I-hormone but this sample also contained a 1000-fold excess of unlabeled I-hormone In both cases, the unbound hormone was removed by washing the membrane preparation and the amount of radioactivity remaining associated with the membranes was measured The following results were obtained:
125 I-hormone only 125 I-hormone plus unlabeled hormone
5000 counts per minute 1500 counts per minute
Which of the following statements is most likely to be TRUE concerning the binding of 125 I-hormone?
A Most of the 125I-hormone binds nonspecifically
B The receptor in these membranes binds to thyroid hormone
C The unlabeled hormone does not compete with 125I-hormone for binding to the receptors
D The signal detected in the absence of unlabeled hormone minus the signal measured in the presence of
unlabeled hormone is a measure of non-specific binding
E Hormone binding triggers release of a second messenger (IP3) from the membrane
29 After optimizing the conditions for measuring specific binding of the hormone to its receptor in the previous experiment (Question 28), a new experiment was conducted in which the amount of membrane was held constant while the concentration of hormone was varied Which of the following graphs best depicts the expected results?
125 I labeled Hormone 125 I labeled Hormone
125 I labeled Hormone 125 I labeled Hormone
125 I labeled Hormone
Trang 730 Cells typically devote at least 30% of their energy expenditure to maintaining a negatively-charged internal environment What is the purpose of establishing such an electrochemical gradient across a biological membrane?
A It stimulates intracellular signaling pathways
B It provides a means of doing work
C It enhances the rate of glycolysis
D It provides the energy for enzymatic reactions
E It stabilizes the structure of the lipid bilayer
31 Vinblastine is a chemotherapeutic agent isolated from the periwinkle plant that binds to tubulin, thereby inhibiting microtubule assembly Which of the following effects would you expect to observe in actively dividing lung carcinoma cells treated with vinblastine?
A inhibited movement of cilia
B disrupted vesicle transport
C aberrant cell division
D Only B and C
E A, B and C
32 Plant cells communicate with their neighbors by transferring small molecules from one cell’s cytosol to the cytosol of another cell This exchange requires which of the following:
A tight junctions
B gap junctions
C nuclear pore complexes
D plasmodesmata
E desmosomes
33 If water containing radioactively labeled hydrogen atoms is applied to a plant, which products of
photosynthesis will become labeled?
A H2O only
B H2O and HCO3-
C C6H12O6
D H2O and C6H12O6
E H2O, C6H12O6 and HCO3-
34 What do cohesion, surface tension and the observation that ice floats in water have in common concerning the properties of water?
A All result from covalent bonding
B All decrease when temperature increases
C All decrease when the pressure of an open system increases
D All result from van der Waals interactions
E All result from hydrogen bonding
35 Suppose you discovered a new kind of photosynthetic organism unlike any other previously found on Earth You repeat Engelmann’s classic experiment using this new organism and observe that oxygen-dependent bacteria cluster near the green and yellow parts of the spectrum Which statement below is the best
conclusion about the new organism?
A This organism uses the highest-energy photons in the visible spectrum
B This organism uses yellow and green light to drive photosynthesis
C This organism does not contain carotenoids
D This organism is an obligate anaerobe
E This organism lacks mitochondria
36 Choose the correct path of electrons during photosynthesis Not all steps are necessarily listed
A NADPH Electron transport chain Calvin cycle Water NADP+
B Sugars NADP+ Calvin cycle Electron transport chain Water
C Water Electron transport chain NADP+ Calvin cycle
D Water Sugars Glycolysis Calvin cycle Electron transport chain
E Calvin cycle Electron transport chain Water NADP+
Trang 837 At one point in human development, tissue connects the fingers and the hand appears to be “webbed.” Enzymes eventually destroy the cells of the webbing and the fingers separate These enzymes are most likely liberated directly from
A vacuoles
B nuclei
C smooth endoplasmic reticulum
D chromosomes
E lysosomes
38 If three molecules of a fatty acid having the formula C 16 H 22 O 2 are each joined to a molecule of glycerol
(C 3 H 8 O 3 ) with a dehydration synthesis reaction, the resulting neutral fat molecule would have the formula
A C51H68O6
B C48H66O6
C C48H72O
D C51H72O8
E C51H74O9
39 Excessive heat or extremes of pH often cause denaturation of proteins, which means that the proteins
A have dissociated into individual monomer subunits
B have degraded into component amino acids
C are no longer in a functional three-dimensional structure
D have lost their glycosylated side chains
E have formed a water-soluble complex with ATP
40 Consider the DNA sequence 5’-GATTACA-3’ If this region of the DNA is transcribed into RNA, the sequence
of the resulting RNA transcript will be
A 5’-TCGGCAC-3’
B 5’-CUAAUGA-3’
C 5’-TGTAATC-3’
D 5’-UGUAAUC-3’
E 5’-GAUUACA’3’
41 The endomembrane system is involved in each of the following functions EXCEPT
A DNA synthesis
B protein synthesis
C lipid synthesis
D secretion of proteins from the cell
E glycosylation of proteins
42 Electrons and protons combine with oxygen to form water How are the specific properties of oxygen
beneficial to the organism that uses it as a final electron acceptor?
A Oxygen is highly reactive and readily accepts electrons
B Oxygen is strongly electronegative and helps pull the electrons through the electron transport chain
C Oxygen allows a maximum output of energy from ATP synthesis
D Oxygen is the only molecule that can act as a final electron acceptor
E Oxygen requires facilitated diffusion so a gradient can be established in the matrix
43 Once transduction of a signal is complete, the receptor and its bound signal molecule are removed from the cell surface by .
A endocytosis
B diffusion
C hydrolysis
D pinocytosis
E exocytosis
Exam continues on the next page
Trang 944 Which of the following statements about chloroplasts and mitochondria is FALSE?
A Both organelles are descended from bacteria
B Both organelles can synthesize ATP using chemiosmosis
C Both organelles contain ribosomes
D Both organelles contain a membrane-bound electron transport system
E Both organelles use organic molecules as a source of high-energy electrons to pump protons
45 As the oxygen concentration decreases in a C3 plant,
A the rate of photorespiration decreases
B the rate of NAD+ oxidation decreases
C the amount of glyceraldehyde-3-phosphate that is synthesized decreases
D Only A and B are correct
E A, B and C are correct
46 Which of the following statements regarding C-4 plants is FALSE?
A They contain both mesophyll and bundle-sheath cells
B They grow in warmer climates with high amounts of sunlight
C They use pyruvate kinase for their initial fixation of CO2.
D They contain Rubisco
E They are common in nature
47 Which of the following is true concerning the ETS in mitochondria (Electron Transport System/Chain)?
A Electrons from FADH2 enter at complex I
B Complexes I, III, and IV are all multiprotein subunits comprised of peripheral proteins
C More ATP is harnessed from the electrons from NADH than FADH2
D The electrons from NADH have less potential energy than the electrons from FADH2
E Electrons are fed in and the only reduction step is the final production of water
48 Select the best choice regarding the molecule shown to the right?
A It is found in DNA and RNA
B It contains a glycosidic bond
C It is the energy currency of the cell
D Only B and C are true
E A, B and C are true
49 In yeast cells living in an oxygen-free environment,
A glucose is produced from CO2
B ethanol is produced during the citric acid cycle
C ethanol is produced after glycolysis
D lactate is produced during glycolysis
E lactate is produced during anaerobic respiration
50 Where do the electrons from NADPH go in the Calvin cycle?
A They are put onto oxygen, just like in cellular respiration
B They are used to regenerate RuBP from G3P
C They are added to 3PGA
D They are transferred to rubisco
E They remain on NADPH to help drive the light reactions
END OF THE EXAM