Download Middle-Term Test Paper on Biochemistry

Examination on Biochemistry
Name:
Student’s number:
1. Choose the best answer for each of the followings, only one choice for each item (30×1 =
30 marks ) :
1) The amino acid with two carboxylic groups is:
A. Lys
B. Gly
C. His
D. Glu
E. Cys
2) Which of the followings about the description on theβ-pleated sheet is correct:
A. The hydrogen bonds in β-pleated sheet are parallel to the length axis of the peptide chain
B. The formation of hydrogen bonds only exists between different peptides
C. The planes of peptide unit in β-pleated sheet are of indentation
D. β-pleated sheet is called as β-turn too
E. Glycine and alanine are not beneficial to the formation of β-pleated sheet
3) Which is incorrect about the depiction of hemoglobin (Hb) and myoglobin (Mb)
A. Both of Hb and Mb contain ferrium
B. Both can combine with oxygen
C. Both are conjugated protein with prosthetic group
D. Both have quaternary structure
E. Both belong to hemoproteins
4) The protein that is eluted first from the chromatography column of gel filtration should be
A. Insulin ( Mr 5 700 )
B. Myoglobin ( Mr 16 900 )
C. cattleβ-lactoglobulin ( Mr 35 000 )
D. Albumin in serum ( Mr 68 500 )
E. Hydrogen peroxidase in horse liver ( Mr 247 500 )
5) The inhibition effect of malonate on succinate dehydrogenase is:
A. Vmax unchanged, Km increased
B. Vmax decreased, Km decreased
C. Vmax increased, Km increased
D. Vmax unchanged, Km decreased
E. Vmax decreased, Km increased
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6) Which is incorrect about the covalent regulation on enzymes:
A. It occurs under the catalysis of another group enzymes
B. The activities of the enzyme definitely increase after it is covalently modified
C. The part of enzyme that is covalently modified is its apoenzyme
D. The major model of covalent modification on enzymes is phosphorylation/
dephosphorylation
E. It is more efficient for the metabolic regulation because of the cascade amplificatory effect
7) Which belongs to synthases (ligases ) class according its EC 4 digitals:
A. A enzyme, EC 1.3.4.2
B. B enzyme, EC 2.4.3.1
C. C enzyme, EC 3.2.1.1
D. D enzyme, EC 5.2.2.3
E. E enzyme, EC 6.2.1.2
8) The denaturation of enzymes will give rise to:
A. The peptide bonds broken, the secondary structure damaged
B. To produce free amino acids or small fragments of peptide
C. Don’t change the primary structure and keep bioactivities
D. The apoenzyme will certainly precipitate in solution
E. The spatial conformation damaged, the stability decreased and bioactivities lost
9) All the statements about the structure of enzyme molecule are true except that _________:
A. Conjugated enzyme consists of apoenzyme and cofactors
B. The specificity of the action of an enzyme depends on its apoenzyme
C. All of cofactors of enzymes are called as coenzyme
D. The combination of some of cofactors with apoenzymes are loose
E. There are some groups among diverse coenzymes that can proceed with the reversible
change
10) Which is error about the narration on glycolysis
A. Glycolysis in diverse tissues only proceed under the anaerobic condition or oxygen
unavailable
B. The location of glycolysis is in cytoplasm
C. The final products of glycolysis are lactate and a few of ATPs
D. There are the same intermediates during the process of glycolysis or aerobic oxidation of
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glucose
E. The only mode to yield ATP during glycolysis is phosphorylation at the substrate level
11) Which is the most key enzyme for the glycolysis as following:
A. Hexokinase
B. Fructose-6-phosphokinase-1
C. Glucose kinase
D. Pyruvate kinase
E. Fructose-6-phosphokinase-2
12) All the following narrations on glycogen in body are correct except that ________:
A. The one of models to storage sugar in animals is glycogen
B. Liver glycogen can release free glucose into bloodstream and compensate blood sugar level
C. The excess glucose absorbed into body can be only converted to glycogen to storage
D. The liver glycogen in human body will be used up after starvation for 24 hours
E. The lactate yielded from muscle glycogen can be used to synthesize glucose in liver via
Cori cycle
13) About the gluconeogenesis, the error is:
A. The process that nonsaccharides are converted to glucose in liver or kidney is called
gluconeogenesis
B. Both amino acids and fatty acids can be converted to glucose
C. Gluconeogenesis doesn’t proceed in muscle tissue
D. Gluconeogenesis is an important pathway which compensate blood glucose level
E. Glucose-6-phosphatase is the enzyme which must need for gluconeogenesis to complement
blood glucose
14) Which fatty acid in the following can not be synthesized by human bodies self?
A. Palmitate
B. Linolenate
C. Oleate
D. Stearate
E. Myristate
15) Which of the following enzymes belongs to the key enzyme for fat mobilization:
A. Protein kinase
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B. Monoglyceride lipase
C. Diglyceride lipase
D. glycerol kinase
E. Hormone-sensitive triglyceride lipase
16) The enzyme which can present both in the pathway of glycolysis or gluconeogenesis is
A. Hexokinase
B. Pyruvate kinase
C. Pyruvate carboxylase
D. Fructose-1,6-diphosphatase
E. Phosphoglycerate kinase
17) All the narrations on the synthesis of fatty acids are correct except that _______:
A. The fatty acid synthase complex exists in cytoplasm
B. Biotin is one of cofactors participating in synthesis of fatty acids
C. During the process of fatty acid synthesis, NADPHs are needed
D. ATPs are not required for the process of synthesis of fatty acids
E. Malonyl CoA is the intermediate in the pathway of fatty acid synthesis
18) The error of the narration related to ketone bodies is:
A. Ketone bodies are the incomplete decompositions of fatty acids in adipose tissue
B. It can feed some small molecules with energy to the extrahepatic tissues
C. Ketone bodies have relatively high solubility in water
D. Ketone bodies can be transported into brain cross the barrier of blood-brain
E. Ketone bodies can replace glucose to be oxidized to yield energy when blood sugar level is
low
19) The enzyme that doesn’t need for -oxidation of fatty acids is:
A. Acyl CoA dehydrogenase
B. β-hydroxyacyl CoA dehydrogenase
C. enoyl CoA hydratase
D. β-ketoacyl CoA transferase
E. β-ketoacyl CoA thiolase
20) Which of the following can participate in substrate level phosphorylation and release
energy?
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A. Succinyl CoA
B. Glucose-6-phosphate
C. UDPG
D. Fructose-1,6-bisphosphate
E. 2,3-bisphosphoglycerate
21) The protein denaturation doesn’t include that______:
A. Hydrogen bonds broken
B. Peptide bonds broken
C. Hydrophobic bonds broken
D. Salt bond ( electrostatic forces ) broken
E. Disulfide bonds broken
22) In the small intestine, the activation of chymotrypsinogen or proelastase mainly depends on :
A. Hydrogen ion ( H+ )
B. Trypsin
C. Pepsin
D. peptidase
E. chymotrypsin
23) If the behavior of an enzyme conform to the kinetics of typical Michaelis-Menten model,
when a double reciprocal or Lineweaver-Burk plot of 1/V0 against 1/[S] is make, Km of the
enzyme will be:
A. The slope of the straight line
B. The absolute value of intercept of the straight line on the 1/V axis
C. The absolute value of intercept of the straight line on the 1/[S] axis
D. The reciprocal of the absolute value of intercept of the straight line on the 1/V axis
E. The reciprocal of the absolute value of intercept of the straight line on the 1/[S] axis
24) About the following narrations of the characters of enzyme actions, which is wrong?
A. The catalytic abilities are quite high
B. There are no by-products
C. The activities may be inhibited
D. There are high specificity
E. The activities are stable
25) About the temperature effects on the velocity of enzyme catalytic reactions, which is
correct in the following:
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A. The enzyme catalytic reactions conform with the rules of temperature effects on chemical
reactions
B. The enzyme activities will lose or decrease when the temperature is too low or too high
C. The higher the temperature, the quicker the velocity of enzyme reaction
D. The optimum temperature is not the characteristic constant of an enzyme
E. Generally, the effects of temperature on the velocity of enzyme reaction is insignificant
26) Which in the following couldn’t be treated as the raw material to participate in
gluconeogenesis
A. Succinate
B. Lactate
C. Alanine
D. Acetyl CoA
E. Pyruvate
27) The degraded products of liver glycogen are:
A. Glucose-1-phosphate and fructose
B. Glucose-1-phosphate and glucose
C. Glucose-6-phosphate and glucose
D. Glucose and fructose-6-phosphate
E. Lactate
28) About the glycolysis, which in the following narrations is correct?
A. It means the process in which glucose is converted to lactate under anaerobic condition
B. Glycolysis is still the major pathway of supplying energy in human body
C. Basically the process of glycolysis is still reversible
D. The hydrogen atoms which are required for the reduction of pyruvate to lactate are
supplied by NADPH + H+
E. The velocity of glycolysis will decrease during the vigorous exercise
29) The reasons which insulin decease blood sugar level involve in various aspects, but not
including:
A. Boost the transportation of glucose
B. Enhance the synthesis of glycogen
C. Accelerate the aerobic oxidation of glucose
D. Decrease the degradation of glycogen
E. Activate the mobilization of fat in adipose tissue
30) About the narrations related to the acetyl CoA in the following, which is not correct:
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A. It may participate in the synthesis of triglyceride
B. It may take part in the synthesis of cholesterol
C. It is concerned with the absorption and transportation of glucose
D. It may be oxidized further to release energy
E. It may be joined with another molecule of acetyl CoA
2. Fill in the missing words and phrases ( 0.5 mark for each blank, 20×0.5 = 10 marks):
1) As you know, there are ________, _________etc belonging to allosteric proteins.
2) The secondary structures of proteins include _________,
_________,
___________,
___________. It is _________ bonds to keep the secondary structure of proteins stable.
3) The methods of protein purification are __________, ____________, ____________etc
4) Update, as you know, there are ___________,
___________ etc which belong to
biocatalysts.
5) The models that can rapidly regulate enzyme activities are ___________, ___________ .
6) Cholesterols can convert to ___________, ___________
and ___________ in human
bodies.
7) Generally, lipoproteins can be classified to five groups, including _________, __________
and __________ etc. ( note: It is ok if you can write down any three of five groups )
3. Explain the concepts as following ( 4 marks for each concept, 8×4 = 32 marks):
1) peptide bond
2) isoenzyme
3) zymogen and its activation
4) active site of enzymes
5) triacylglycerol mobilization
6) ketone bodies
7) tertiary structure of proteins
8) Glycogen synthesis
4. Answer the following questions ( 6 marks for each item, 3×6=18 marks ):
1) Can you list the fates of glucose-6-phosphate in human bodies? Write down the key
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enzymes for each pathway.
2) Why do some patients who are deficiency of G-6-PD ( glucose-6-phosphate dehydrogenase )
can incur hemolysis when they have been administered some anti-malaria drugs ?
3) What are the fates of acetyl CoA in eukaroytes? Where is the location of these pathways in
cells, respectively?
5. Answer the following question in detail (10 marks ):
Why will it be obese when carbohydrates have been fed up too much? Could you explain
the reasons according to the biochemical knowledge that you have learned?
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Middle-Term Test Paper on Biochemistry
For the class of oversea undergraduates
Keys to Test Paper
1. Multiple choice
1)-D
2)-C
3)-D
4)-E
11)-B
12)-C
13)-B 14)-B 15)-E
16)-E
17)-D 18)-A 19)-D
20)-A
21)-B
22)-B
23)-E
26)-D
27)-C 28)-A 29)-E
30)-C
24)-E
5)-A 6)-B
25)-D
7)-E
8)-E
9)-C
10)-A
2. Fill in blanks
1) Hb, Protein kinase A ( or other proteins with quaternary structure )
2) -helix, -pleated sheet, -turn, random coil, hydrogen bonds
3) gel filtration chromatography, ion exchange chromatography, affinity chromatography
(or ammonium sulfate precipitation, dialysis, ultracentrifugation, native PAGE, isoelectric
focusing, so on )
4) enzymes, ribozymes ( or any two enzymes , deoxyribozymes )
5) allosteric regulation, covalent modification ( chemical modification )
6) bile salts, steroid hormones, vitamin D3
7) CM ( chylomicrons), VLDL ( very low density lipoproteins ), LDL (low density lipoproteins )
( or IDL----intermediate density lipoproteins, HDL----high density lipoproteins )
3. Explain the following concepts
1) Peptide bond
Peptide bond is a covalent bond between the -amino group of one amino acid and the
-carboxyl group of another. ( Peptide bonds are the main linkage bonds in peptide chain of
protein )
2) isoenzymes
Isoenzymes ( isozymes ) are different forms of an enzyme which catalyze the same reaction, but
exhibit different physical or kinetic properties, such as isoelectric point, pH optimum, substrate
affinity or effect of inhibitors.
3) zymogen and its activation
Several enzymes are synthesized as larger inactive precursor forms called proenzymes or
zymogens.
That process involved irreversible hydrolysis of one or more peptide bonds on a zymogen is
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termed the activation of zymogen.
4) active site of enzymes
The active site of an enzyme is the region of the enzyme which binds the substrate to form an
enzyme-substrate complex, and transforms it into product.
The active site is a three-dimensional entity, often a cleft or crevice on the surface of the protein,
in which the substrate is bound by multiple weak interactions.
5) triacylglycerol mobilization
The process which triacyglycerols in adipose tissue are hydrolyzed by a suitable lipase to their
constituent fatty acids and glycerol with release of free fatty acids and glycerol into plasma is
termed as mobilization of triglyceride ( or lipolysis ).
6) ketone bodies
Ketone bodies are products of fatty acids breakdown incompletely in liver, including
β-hydroxybutyrate, acetoacetate, acetone.
7) tertiary structure of proteins
The tertiary structure of a protein refers to spatial relationship among all
amino acids in a polypeptide; it is the complete three-dimensional structure
of the polypeptide.
8) Glycogen synthesis
G
G-1-P
G-6-P
hexokinase
Phosphoglucomutase
UDP-glucose
pyrophosphorylase
UDP-G + PPi
UTP
Glycogen
synthase
Gn
Glycogen
(Gn+1)
Glycogen synthesis is the process of glycogen formation from glucoses catalyzed by glycogen
synthase and other enzymes related to glycogen synthesis.
4. Answer the following questions ( 6 marks for each item, 3×6=18 marks ):
1) Can you list the fates of glucose-6-phosphate in human bodies? Write down the key enzymes
for each pathway.
! glucose-6-phosphate  glucose-1-phosphate glycogen synthesis; key enzyme is
glycogen synthase (2 marks )
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!! glucose-6-phosphate  fructose-6-phosphate    pyruvate  lactate
acetyl CoA  TAC
key enzymes: hexokinase, phosphofructokinase, pyruvate kinase;
above enzymes + pyruvate dehydrogenase complex, citrate synthase, isocitrate dehydrogenase,
-ketoglutarate dehydrogenase complex ( 2 marks )
!!! glucose-6-phosphate  glucose + phosphate ( gluconeogenesis )
key enzyme: glucose-6-phosphatase ( 1 mark )
!V glucose-6-phosphate   6-phosphoglucono--lactone  pentose phosphate pathway
key enzyme: glucose-6-phosphate dehydrogenase 1mark )
2) Why do some patients who are deficiency of G-6-PD ( glucose-6-phosphate dehydrogenase )
can incur hemolysis when they have been administered some anti-malaria drugs ?
Because of the deficiency of G-6-PD  pentose phosphate pathway  (G-6-PD is the key
1 mark
enzyme of the pentose phosphate pathway )  NADPH  GSH  ( GSH needs NADPH to
1 mark
1 marks
1 marks
maintain its concentration )  when the patient has taken anti-malaria drugs ( containing
1 mark
oxidative property ), the cell membrane of erythrocytes are easily damaged (because of lack of
1 mark
GSH )  hemolysis
3) What are the fates of acetyl CoA in eukaroytes? Where is the location of these pathways in
cells, respectively?
! acetyl CoA  TAC
1 mark
!! acetyl CoA    ketone bodies
1 mark
in mitochondria
0.5 mark
!!! acetyl CoA    fatty acids
1 mark
in cytoplasm
0.5 mark
!V acetyl CoA    cholesterols
1 mark
in cytoplasm
in mitochondria
0.5 mark
0.5 mark
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5. Answer the following question in detail (10 marks ):
Why will it be obese when carbohydrates have been fed up too much? Could you explain
the reasons according to the biochemical knowledge that you have learned?
The key to the question:
During the synthesis of triacylglycerol, it needs acyl CoA + -phosphate glycerol,
1.5 marks
The process of the synthesis of TAG
1.5 marks
The
1.5
How
How
How
synthesis of acyl CoA come from acetyl CoA,and NADPH, as well as energy
marks
does the acyl CoA come from glucose, 1.5 marks
dos the NADPH come from pentose phosphate pathway 1.5 marks
does the energy come from glucose metabolism
1.5 marks
-phosphate glycerol comes from dihydroxyacetone phosphate from glucose 1 mark
When the glucose is in excess, it will convert to fat through the above pathways
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