中国大学MOOC慕课爱课程(3)--试卷(英语)及答案网课刷课

武汉大学生命科学学院
2012－2013学年度第一学期期末考试
《生物化学》试卷（A卷）正确答案
C o l l e g e o f L i f e S c i e n c e s,W u h a n U n i v e r s i t y
B i o c h e m i s t r y F i n a l E x a m
(2013.1.9)
Name__________Student No.Major__________Score__________ 1．Multiple choice (1 point each, 25 points total)
__1)According to the fluid mosaic model of cell membranes, which type of molecule spans the membrane from its inner to outer surface?
A.Cholesterol
B.Phospholipids
C.Protein
D.triacylglycerol
__2)If a mutant enzyme is found to have the same K m but a lower V max, it is most likely that energy of the transition state
A.has remained the same
B.has decreased
C.has increased
D.has decreased substrate binding
__3)In an erythrocyte undergoing glycolysis, a sudden increase in the concentration of the following would lead to the increase of glycolysis EXCEPT
A.[AMP]
B.[Citrate]
C.[fructose-1,6-bisphosphate]
D.[fructose-2,6-bisphosphate]
__4). Acetyl groups (e.g. for lipid biosynthesis) are transported out of the mitochondria indirectly using
A.acetyl carnitine.
B.acetyl phosphate.
C.citrate.
D.malate.
__5). The source of oxygen for O2 production during photosynthesis by higher plants is
A. CO2
B. HCO3 -
C. H2O
D. ATP
__6). HMG-CoA reductase is the rate limiting enzyme in synthesis of:
A.low molecular weight triglycerides
B.cholesterol
C.High molecular weight triglycerides
D.Chylomicrons
__7). The final electron acceptor in the electron transport chain is
A.FAD
B.NAD+
C.CoQ
D.Oxygen
__8). Absorbed lipid is transported away from the gut mucosal cells in the form of
A.VLDL
B.LDL
C.HDL
D.Chylomycrons
__9). During DNA replication the negative supercoiling of the bacterial chromosome is maintained by the action of
A.DNA gyrase.
B.DnaB helicase.
C.DNA ligase.
D.Primase.
__10). Which of the following is true?
A.Liquid and solid water have the same number of hydrogen bonds per molecule of
water
B.Liquid water has more hydrogen bonds per molecule than does solid water
C.Solid water has more hydrogen bonds per molecule than does liquid water
D.Hydrogen bonding is a major factor in the structure of gaseous water
__11). Electrons from complex I are transferred directly to which of the
following electron transport components?
plex II
plex III
C.cytochrome c
D.ubiquinone
12). Which diagram best depicts the state immediately following peptide bond formation between the initiating met and the second amino acid (aa2) of the peptide prior to the first translocation step (movement of the ribosome by one codon toward the 3' end)?
__13). For the first five steps of glycolysis, the appropriate sequence of enzymes is:
A.phosphofructokinase (PFK).
B.hexokinase / glucokinase.
C.fructose bisphosphate aldolase.
D.Phosphoglucoisomerase.
E.triose phosphate isomerase
A. A, C, B, E, D
B. B, D, C, E, A
C. B, D, A, C, E
D. D, B, A, C, E
__14). DNA replication originates at the indicated origin of replication. Which segment(s) serve as template(s) for lagging strand synthesis?
A. B and D
B. A and C
C. A and B
D. A and D
__15). Which of the following is meant by the statement that glucose and mannose are epimers?
A. One is an aldose and the other is a ketose
B. One is a pyranose and the other is a furanose
C. They are mirror images of each other
D. They differ only in the configuration about one carbon atom
16).The first three reactions of β-oxidation of saturated fatty acids are analogous to which sequence of metabolic reactions discussed in the TCA cycle?
A. succinate → fumarate → malate → oxaloacetate
B. isocitrate →α-ketoglutarate → succinate → fumarate
C. oxaloacetate → citrate → isocitrate →α-ketoglutarate
D. phosphoenolpyruvate → pyruvate → acetyl-CoA → citrate
__17). If glucose was labeled with 14C at carbon #6, after going through glycolysis, which carbon of pyruvate would have the 14C?
A. carboxyl carbon
B. ketone carbon
C. methyl carbon
D. the 14C would be lost as CO2
__18). The main source(s) of NADPH for fatty acid biosynthesis is (are):
A. TCA cycle.
B. oxidative phosphorylation.
C. malic enzyme and the pentose phosphate pathway.
D. glycolysis.
__19). For an enzyme-catalyzed reaction, the initial velocity was determined at two different concentrations of the substrate. Which of the following would be closest to the value of K m?
[S] (mM)Vo(mM/min)
1.0
2.0
4.0 2.8
A.0.17 mM
B.2.7 mM
C.0.60 mM
D.1.7 mM
20). Which amino acids are most likely to be found in the transmembrane spanning domain of a protein such as glycophorin?
A. Serine and threonine
B. Glutamine and asparagine
C. Lysine and arginine
E.Leucine and isoleucine
21). An obese individual is brought to the emergency room by a concerned friend. The patient has been on a self-imposed "starvation diet" for four months, and has lost 60 pounds while consuming only water and vitamin pills. If extensive blood studies were performed, which of the following would be expected to be elevated?
A. Acetoacetic acid
B. Alanine
C. Bicarbonate
D. Glucose
22) What is the importance of the purine nucleoside cycle?
A. It participates in the conversion of purines into pyrimidines.
B. It generates fumarate, which inhibits the formation of AMP from IMP.
C. It provides fumarate as an anaplerotic enhancement of the citric acid cycle.
D. It is used in energy metabolism in the liver.
23) Fatty acids are mobilized from adipose cells in response to all of the hormones EXCEPT:
A. ACTH (adrenocorticotropic hormone).
B. glucagon.
C. insulin.
D. epinephrine (adrenaline).
__24). The complete oxidation of a molecule of Palmitoyl-CoAin respiring mitochondria to CO2 and H2O would cause a net gain of how many ATP?
A.130
B.128
C.108
D.102
__25) The following compounds represent intermediates in β-oxidation:
The order of generation of these intermediates in one cycle of β-oxidation is:
A. III, IV, I, II
B. III, I, IV, II
C. III, IV, II, I
D. III, II, I, IV
2. Match with the appropriate subcellular locations (0.5 point each, 5 points total)
1) Glyoxylate cycle ___F____
2) Pentose phosphate pathway ___A____
3) Glycolysis ___A____
4) -oxidation ___G____
5) The electron transport chain ___C____
6) Pyruvate dehydrogenase ___G____
7) Ornithine transcarbamoylase ___G____
8) Final step of urea formation ___A____
9) Fatty acid biosynthesis __A____
10) Insulin receptor ___D____
A. Cytoplasm
B. Lysosome
C. Inner mitochondrial membrane
D. Cell membrane
E. Endoplasmic reticulum
F. Glyoxysome
G Mitochondrial matrix
H. Nuclear area or nucleoid
I. Cell wall
3. Fill-in (0.5 point for each blank, 15 points total)
1)Animal cells have evolved two important shuttles to transfer NADH across the inner
mitochondrial membrane:_the glycerol phosphate shuttle __ and_ the malate-aspartate shuttle
2)The two nitrogen and one carbon atoms in urea synthesis (urea cycle) are from _ NH4+,
CO2, and aspartate __.
3)____ Glutamate ___________ and ___ glutamine ____ are the primary nitrogen donor
molecules in a transamination reaction.
4)Isoprenoids are a large group of biomolecules with repeating units derived from
isopentenyl pyrophosphate.There are two types of isoprenoids, _ terpene_ and_ cholestrol_.
5)Nitrogen fixation is the formation of NH4+ from N2.
6)The first law of thermodynamics states that the total energy of an isolated system is
c onserve
d /unchanged/constant. Th
e second law states that the universe tends to become
more disorganized/disordered .
7)In photosynthesis, electrons flow from H2O to NADP+, driven by light energy absorbed
at the reaction centers.
8)Most aspartic proteases have a tertiary structure consisting of two lobes (N-terminal and
C-terminal) with approximate two-fold symmetry. But HIV-1 protease is a homodimer, with each subunit contributing a catalytic Asp residue.
9)The thousands of proteins in cells can be separated and purified on the basis of size and
electrical charge . Proteins tend to be least soluble at a pH value close to their isoelectric point .
10)Increasing ionic strength at first increases the solubility of proteins, then decreases it.
Protein subunit interactions depend on weak forces. Separation can be achieved with treatment of (name two conditions):_______, ________.
- extreme pH
- 8M urea
- 6M guanidine HCl
- high salt concentration (usually ammonium sulfate)
11) The major fuel depots in animals are glycogen in liver and muscle; triacylglycerols in adipose tissue; and protein, mostly in skeletal muscle. The usual order of preference for use of these is glycogen > triacylglycerol > protein
12) In ETC, c omplex II does not directly contribute to the proton concentration gradient across the inner mitochondrial membrane. Instead, it supplies electrons from the oxidation of succinate midway along the ETC.
4. Definition (2.5 points each, 15 points total)
1)Prosthetic group (as in enzymology): tightly bound co-enzyme
2)Transition state analogs:Transition state analogs (TSAs) are stable molecules that are
chemically and structurally similar to the transition state
3)Proteomics: large scale study of proteins
4)The Cori Cycle: the metabolic pathway in which lactate produced by anaerobic glycolysis
in the muscles moves to the liver and is converted to glucose, which then returns to the muscles and is converted back to lactate
5)Allosteric regulation is the regulation of an enzyme or other protein by binding an
effector molecule at the protein's allosteric site (that is, a site other than the protein's
active site).
6)Cell signalling is part of a complex system of communication that governs basic cellular
activities and coordinates cell actions.
5. Short questions (4 points each, 20 points total)
1) The biosynthesis and degradation pathways are different. Please discuss the major differences between fatty acid breakdown and biosynthesis
●Intermediates in synthesis are linked to
-SH groups of acyl carrier proteins (as compared to -SH groups of CoA)
●Synthesis in cytosol; breakdown in mitochondria
●Enzymes of synthesis are one polypeptide, the fatty acid synthase
●Biosynthesis uses NADPH/NADP+; breakdown uses NADH/NAD+
2) Name at least three different modes of enzyme regulation you can think of. Which type of modification of the protein is required in each case?Is the modification reversible or irreversible?
(1) Allosteric control. Binding (at a regulatory site) of a regulatory molecule in addition to the substrate. Reversible.
(2) Proteolytic activation. Peptide bonds in the protein are cleaved (hydrolysed) by a protease. Irreversible.
(3) Reversible covalent modification, e.g. phosphorylation. Phosphorylation is catalysed by protein kinases, which transfers a phosphate group from ATP to a Ser, Thr or Tyr residue on the enzyme. The reverse, i.e. removal of the phosphate group is performed by protein phosphatases (or protein phosphorylases).
(4) Binding of regulatory protein. Reversible.
(5) Gene regulation. Does not affect the properties of the enzyme, but the amount.
3) What would be the consequences of a carnitine deficiency for fatty acid oxidation?
A carniting deficiency would presumably result in defective or limited transport of fatty acids into the mitochondrial matrix and reduce rates of fatty acid oxidation.
4) What are the anaplerotic, or “Filling Up” reactions for TCA cycle? Please give an
example.
Anaplerotic reactions replenish the TCA cycle intermediates. Examples include PEP carboxylase and pyruvate carboxylase, both of which synthesize oxaloacetate from
pyruvate.
5) Make a list of the ways that DNA replication in eukaryotes differs from transcription
in prokaryotes.
1.Timing is limited to a specific period referred to as the S phase (vs throughout life
cycle).
2.Replication rate is slower, approximately 50 nucleotides/sec per rep fork (vs1000).
3.Multiple replicons (vs one) speed overall replication to just a few hours.
4.Okazaki fragments are 100-200 nucleotides long. (vs 1000-2000)
6. Questions (10 points each, 20 points total)
1)Demonstrate your knowledge of biochemistry by showing the sequence(with structures) of reactions u sing pyruvate (labeled with 14C in its keto group) via the pyruvate dehydrogenase reaction and the TCA cycle. Where would the carbon label be at the end of one turn of the TCA cycle? Where would the carbon label be at the end of the second turn of the cycle?
The carbonyl carbon of acetyl-CoA is fully retained through on turn of the cycle, but is lost completely in a second turn of the cycle.
2) The sequence of reactions from glucose to pyruvate is similar in most organisms and most types of cells. In contrast, the fate of pyruvate is variable. Discuss the fate of pyruvate under different metabolic conditions. Please show the biochemical reactions involved. 1) in yeast and several other microorganisms; 2) in muscle during intense activity; 3) inside mitochondria by the oxidative decarboxylation of pyruvate; 4) converstion to oxaloacetate; 5) transaminated to form Alanine.
Answer-
1. Ethanol is formed from pyruvate in yeast and several other microorganisms. The first step is the decarboxylation of pyruvate. This reaction is catalyzed by pyruvate decarboxylase, which requires the coenzyme thiamine pyrophosphate.
+.
2. Lactate is formed from pyruvate in a variety of microorganisms in a process called lactic acid fermentation. The reaction also takes place in the cells of higher organisms when the amount of oxygen is limiting, as in muscle during intense activity. The reduction of pyruvate
by NADH to form lactate is catalyzed by lactate dehydrogenase.
Figure-2- showing the conversion of pyruvate to Lactate
3. Acetyl co A – Only a fraction of the energy of glucose is released in its anaerobic conversion into ethanol or lactate. Much more energy can be extracted aerobically by means of the citric acid cycle and the electron-transport chain. The entry point to this oxidative pathway is acetyl coenzyme A (acetyl CoA), which is formed inside mitochondria by the oxidative decarboxylation of pyruvate.
4. Oxaloacetate- Pyruvate can be converted to oxaloacetate. Mitochondrial pyruvate carboxylase catalyzes the carboxylation of pyruvate to oxaloacetate, an ATP-requiring reaction in which the vitamin biotin is the coenzyme. Biotin binds CO2 from bicarbonate as carboxybiotin prior to the addition of the CO2 to pyruvate.
Figure –3- showing the conversion of pyruvate to oxaloacetate
The Oxaloacetate can be subsequently used for the synthesis of Aspartate, phosphoenol pyruvate or be utilized in the TCA cycle depending upon the need of the cell.
5. Alanine- Pyruvate can be transaminated to form Alanine as per need.
Figure-4- showing the conversion of Pyruvate to Alanine by transamination 课程答案网课刷课flyingjgh。