18 - biochemistry mcqs - 154 to 155

154) True about Heparin is

a. Basic in nature

b. Contains Glucronic Acid

c. LMW Heparin selectively inhibit Xa

d. no effect on platelet

Answer : c) LMW Heparin selectively inhibit Xa

Reference: Chaterjee 6^th Edition Page 39

155) About PGE₂

a. Synthesized in fetus

b. Closes the ductus arteriosus

c. Both

d. None

Answer : b) Closes the ductus arteriosus

Reference: Tripathi 5^th Edition Page 159

17 - biochemistry mcqs - 143 to 153

143) Urea synthesized mainly in

a. Liver

b. Heart

c. Kidney

d. brain

Answer : Liver

Reference: Chaterjee 6^th Edition Page 411

144) The End product of purine metabolism is

a. Urea

b. Creatinine

c. Uric Acid

d. GLycine

Answer : c) Uric Acid

Reference: Chaterjee 6^th Edition Page 212

145) Folic acid antagonist for Cancer is

a. Methotrxate

b. Vincristine

c. Cyclosporine

d. Azathioprine

Answer : a) Methotraxate

Reference: Tripathi 5^th Edition Page 772

146) In Galactosemia the Cataract is due to the production of

a. Sorbital

b. Galactose

c. Glucose

d. Galactositol

Answer : d) Galactositol

Reference: Chaterjee 6^th Edition Page 312

147) Following are causes of Vitamin B 12 deficiency except

a. Strict vegetarian

b. Blind loop Syndrome

c. Diphyllobothrium latum infection

d. Chronic Blood loss

Answer :D) Chronic Blood Loss

Reference: Chaterjee 6^th Edition Page 182

148) Hyaluronic acid is made up of

a. N-Acetyl Glusosamine

b. D- GLucuronic Acid

c. Both

d. None

Answer : C) Both

Reference: Chaterjee 6^th Edition Page 38

149) Fluoride inhibits

a. enolase

b. Glukokinase

c. Aldolase

d. Phosphofructokinase

Answer : a) Enolase

Reference: harper 24^th Edition Page 178

150) Thiamine rich in

a. Unpolished rice

b. Fish

c. Soyabean

d. All of these

Answer : a) Unpolished rice

Reference: Chaterjee 6^th Edition Page 159

151) The initial change seen in Hyperventilation regarding PCO₂ is

a. No changes

b. Increased PCO₂ with increased pH

c. Normal PCO₂ with increased pH

d. Decreased PCO₂ with increased pH

Answer : d) Decreased PCO2 with increased pH

Reference: Chaterjee 6^th Edition Page

152) Characteristics of Insulin resistant syndrome all except

a. Hypoglycemia

b. May be associated with PCOD

c. Obesity

d. Hyperglycemia

Answer : Hypoglycemia

Reference: Harrison 15^th Edition Chapter 77

153) FSH and LH are Produced by

a. Anterior pituitary

b. Hypothalamus

c. Placenta

d. Ovary

Answer : A) Anterior Pituitary

Reference: Ganong 22^nd Edition Page 397

16 - biochemistry mcqs - 132 to 142

132) Vitamin useful in the treatment of Hartnup’s disease is

a. Biotin

b. Niacin

c. Folic Acid

d. Thiamine

Answer : b) Niacin

Reference: Harrison 15^th Edition Chapter 353

133) Ketogenic amino acid

a. Leucine

b. Valine

c. Alanine

d. Tryptophan

Answer : Leucine

Reference: harper 24^th Edition Page 310

134) Maple Syrup Urine Disease is due to defect in the metabolism of

a. Unbranched aminoacid

b. Phenyl alanine

c. Branched Chain Amino Acid

d. Tyrosine

Answer : c) Branched Chain Amino Acid

Reference: Chaterjee 6^th Edition Page 456

135) Why muscle glycogen is not useful in elevation of Glucose level of blood because muscle does not contain

a. Glucose – 6 – phosphatase

b. Phosphorylase

c. Cyclic AMP

d. Protein Kinase

Answer : a) Glucose – 6 – phosphatase

Reference: Chaterjee 6^th Edition Page 291

136) Irreversible enzyme step all except –

a. phosphofructokinase

b. Phosphohexose isomerase

c. hexokinase

d. Pyruvate kinase

Answer : B) Phosphohexose isomerase

Reference: Chaterjee 6^th Edition Page 306

137) NADPH not produced for fatty acid synthesis from

a. HMP shunt

b. malic enzyme

c. lactic dehydrogenase

d. isocitrate dehydrogenase

Answer : c) lactic dehydrogenase

Reference: Chaterjee 6^th Edition Page 355

138) The main role of Vitamin K is

a. Carboxylation

b. Formatiuon of active succinate

c. Heme systhessis

d. Synthesis of Fatty acid

Answer : a) Carboxylation

Reference: Chaterjee 6^th Edition Page 155

139) Enterohepatic circulation of bile salt is affected and that leads to

a. Vitamin K deficiency

b. Hypertension

c. Hemolytic anemia

d. Diabetes Insipidus

Answer : a) Hemolytic Anemia

Reference: Chaterjee 6^th Edition Page 155

140) Bile salts is produced from

a. Cholesterol

b. Amino acids

c. Glycogen

d. Lecithin

Answer : a) Cholesterol

Reference: Ganong 22^nd Edition Page 501

141) Vitamin K deficiency occurs in

a. Obstructive Jaundice

b. Hemolytic Jaundice

c. Prehepatic Jaundice

d. Secondaries liver

Answer : a) Obstructive Jaundice

Reference: Chaterjee 6^th Edition Page 155

142) Antiracchitic Vitamin D is activated in the following organ

a. Muscle

b. Lungs

c. Kidney

d. Intestine

Answer : c) Kidney

Reference: Ganong 22^nd Edition Page 388

15 - biochemistry mcqs - 121 to 131

121) Stop Codons

a. UAG

b. UGA

c. UAA

d. All

Answer (d) All of the above

Reference: Harper 27^th Edition Page 366

122) Weakest bond

a. Vanderwalls bond

b. Covalent

c. Ionic

d. Gravitational

Answer (a) Vanderwalls bond

Reference: Harper 27^th Edition Page 7

123) All of the following are involved in various steps of Electron transport chain except:

a. NADP

b. NAD

c. Co Enzyme Q

d. CoA

Answer (a) NADP

Reference: Harper 27^th Edition Page 103

124) Consumption of Ethanol leads to increased levels of

a. Lactate

b. acetaldehye

c. NADH

d. All of the above

Answer: All of the above

Reference: Harper 27^th Edition Page 225

125) Un acceptable type of Missence Mutation is

a. Hb M

b. Hb Hikari

c. Hb S

d. None

Answer : (A) Hb M

Reference: Vasudevan 2^nd Edition Page 308

New Hb	Effect
Hb Bristol	No functional Change
Hb Sydney	No functional Change
Hb Hikari	Acceptable Mistake
Hb S	Partially Acceptable Mistake
Hb M	Unacceptable Mutations
Hb Tak	Nonsense Mutations
Hb Constant Spring	Production of “Run on Polypeptide”

126) Pentose Sugar in Nueclic acid

a. Ribose

b. Deoxyribose

c. Both

d. None

Answer (C ) Both

Reference: Chaterjee 6^th Edition Page 27 and Harper 27^th Edition Page 298

127) Vibration Property of Molecules is checked by

a. Infra red Spectroscopy

b. Electron Microscopy

c. Light Microscopy

d. None of the above

Answer: a) Infra red Spectroscopy

Reference: See Wikipedia, Infrared spectroscopy, http://en.wikipedia.org/wiki/Infrared_spectroscopy (optional description here) (as of Nov. 6, 2006, 21:27 GMT).

Infrared spectroscopy works because chemical bonds have specific frequencies at which they vibrate corresponding to energy levels. The resonant frequencies or vibrational frequencies are determined by the shape of the molecular potential energy surfaces, the masses of the atoms and, eventually by the associated vibronic coupling. In order for a vibrational mode in a molecule to be IR active, it must be associated with changes in the permanent dipole. In particular, in the Born-Oppenheimer and harmonic approximations, i.e. when the molecular Hamiltonian corresponding to the electronic ground state can be approximated by a harmonic oscillator in the neighborhood of the equilibrium molecular geometry, the resonant frequencies are determined by the normal modes corresponding to the molecular electronic ground state potential energy surface. Nevertheless, the resonant frequencies can be in a first approach related to the strength of the bond, and the mass of the atoms at either end of it. Thus, the frequency of the vibrations can be associated with a particular bond type.

Simple diatomic molecules have only one bond, which may stretch. More complex molecules may have many bonds, and vibrations can be conjugated, leading to infrared absorptions at characteristic frequencies that may be related to chemical groups. The atoms in a CH₂ group, commonly found in organic compounds can vibrate in six different ways, symmetrical and asymmetrical stretching, scissoring, rocking, wagging and twisting.

In order to measure a sample, a beam of infrared light is passed through the sample, and the amount of energy absorbed at each wavelength is recorded. This may be done by scanning through the spectrum with a monochromatic beam, which changes in wavelength over time, or by using a Fourier transform instrument to measure all wavelengths at once. From this, a transmittance or absorbance spectrum may be plotted, which shows at which wavelengths the sample absorbs the IR, and allows an interpretation of which bonds are present. This technique works almost exclusively on covalent bonds, and as such is of most use in organic chemistry. Clear spectra are obtained from samples with few IR active bonds and high levels of purity. More complex molecular structures lead to more absorption bands and more complex spectra. The technique has been used for the characterization of very complex mixtures however.

128) The investigation for Thiamine deficiency is

a. RBC Transketalose

b. Blood Sugar

c. Serum Creatinine

d. All of the above

Answer : A) RBC Transketolase

Reference: Harper 27^th Edition Page 497

129) Casals Necklace Pattern is seen in

a. Thiamine Deficiency

b. Riboflavin Deficiency

c. Niacin Deficiency

d. All of the above

Answer C) Niacin Deficiency

Reference: Achar 3^rd Edition Page 89

130) All are examples of detoxication reactions except

a. Oxidation

b. Reduction

c. Hydrolysis

d. None of the above

Answer (d)None of the above

Reference: Chaterjee 6^th Edition Page 483

131) Vitamins needed for the synthesis of Co Enzyme A

a. Pyridoxine

b. Pantothenic Acid

c. Both

d. None

Answer C) Both

Reference: Chaterjee 6^th Edition Page 167

14 - biochemistry mcqs - 108 to 120

108) If the pH is 7.4 then the Hydrogen Ion concentration is

a. 40 mmol/ml

b. 7.4

c. 50

d. None of the above

Answer (a) 40 mmol/ml

Reference: Harper 27^th Edition Page 9

Ä When pH is 7.4, the H+ ion concentration is 40 nanomoles/L

109) Anion gap

a. Is the difference between the unmeasured anion and cation

b. Is the difference Measured cations and Anion

c. Both

d. None

Answer (c) Both of the above

Reference: Chaterjee 6^th Edition Page 630

110) Trypsin is a

a. Serine Protease

b. Maltase

c. Lipase

d. None of the above

Answer : a) Serine Protease

Reference: Chaterjee 6^th Edition Page 397

111) Scurvy is due to deficiency of

a. Vitamin A

b. Vitamin C

c. Vitamin B₁

d. Vitamin B₂

Answer (b) Vitamin C

Reference: Chaterjee 6^th Edition Page 158

112) All of the following components are the common substance with Anti Oxidant properties Except

a. Vitamin D

b. Vitamin C

c. Vitamin E

d. Selenium

Answer a) Vitamin D

Reference: Chaterjee 6^th Edition Page 128, 129

113) In India the major source of Vitamin D is

a. Sunlight

b. Injections

c. Diet

d. None of the above

Answer (a) Sunlight

Reference: KD Tripathi 5^th Edition Page 303

114) A person on a fat free carbohydrate rich diet continues to grow obese. Which of the following lipoproteins is likely to be elevated in his blood?

a. Chylomicrons.

b. VLDL.

c. LDL.

d. HDL.

Answer: 2. VLDL.

Reference : Harper 25th Edition Page 296, Harrison 15th Edition Page 2250

115) Enzyme defcint in Alkaptanuria is

a. Homogentiase Oxidase Deficiency

b. Folate Synthetase

c. DNA Gyrase

d. Transpeptidases

Answer (a) Homogentiase Oxidase Deficiency

Reference: Harper 27^th Edition Page 259

116) The enzyme deficient in Criggler - Najjar Syn Type I is

a. Folate Synthetase

b. DNA Gyrase

c. Transpeptidases

d. Udp Glucornyl Transferase

Answer: (d) Udp Glucornyl Transferase

Reference: Harper 27^th Edition Page 270

117) Which of the following is not a HomopolySaccaride

a. Heparin

b. Dextran

c. Inulin

d. Starch

Answer Heparin

Reference: Chaterjee 6^th Edition Page 35

118) Fatty acid synthesis complex does not contain this enzyme used in fatty acid synthesis

a. Acetyl coa carboxylase

b. Enoyl reductase

c. Ketoacyl reductase

d. Hydratase

Answer (a) Acetyl coa carboxylase

Reference: Harper 27^th Edition Page 197

119) Metabalic alkalosis occurs in

a. Recurrent vomiting

b. Diabetic Ketosis

c. Diarrhoea

d. All of the above

Answer (a) Recurrent Vomiting

Reference: Harrison 16^th Edition Page 268

120) Major anion in ECF

a. Protein

b. Cl-

c. HCO3

d. None of the above

Answer (B) Cl^-

Reference: Ganong 22^nd Edition Figure 1.27

13 - biochemistry mcqs - 98 TO 107 - glycolysis

98 - Thiamine pyrophosphate , functions as an ________ sink that acts to stabilize the carbon ion adduct formed during the decarboxylation of pyruvate .

answer is electron sink .

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99 - phosphoglycerate kinase converts 1 , 3 bisphosphoglycerate to 3 phosphoglycerate and forms an ATP .

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100 - the irreversible rate determining step in glycolysis is catalysed by ?

answer is PFK .

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101 - pentose phosphate pathway is also called hexose monophosphate shunt .

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102 - the molecule which conserves the free energy of metabolite oxidation for ATP synthesis ?

NADH .

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103 - The molecule which conserves the free energy of metabolite oxidation for reductive biosynthesis ?

NADPH .

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104 - 6 phosphogluconolactonase ------- 6 - phosphogluconate

6 phosphogluconate dehydrogenase ------------ RU5P

glucose 6 phosphate dehdrogenase -------- first committed step in HMP pathway

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105 - The process of fermentation has greater thermodynamic efficacy under physiological conditions than under standard biochemical conditions ?

the above statement is true .

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106 - under aerobic conditions glucose is oxidised during glycolysis and the coenzyme _________ is reduced and subsequently oxidised in a process known as electron transport ?

NAD +

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107 - in muscle a 10 % decrease in ATP concentration , results in a 100 % increase in ADP concentration and 400 % increase in AMP concentration .

true .


TO READ COMPLETELY ABOUT GLYCOLYSIS CLICK HERE

TO KNOW MORE ABOUT HMP SHUNT CLICK HERE

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12 - biochemistry mcqs - 87 to 97 - glycolysis

87 - lactose build up in the muscle during vigorous activity causes muscle fatigue and soreness .

the above statement is false . it is glycolytically generated acid that causes muscle fatigue and soreness .

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88 - when NADPH is needed from the pentose phosphate pathway , excess ________ is converted to glycolytic intermediates by a sequence of reactions which can operate in reverse .

ribulose - 5 - phosphate .

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89 - which state of PFK , does AMP preferentially bind ?

a- to the R state
b- to the T state
c- to both states without any preference
d- to neither

answer is a . to the R state .

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90 - yeast alcohol dehydrogenase and mammalian liver alcohol dehydrogenase , both require ____

a- Mg + 2
b- Zn + 2
c- calcium
d- iron

answer is b . ZINC .

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91 - glyceraldehyde 3 phosphate is phosphorylated to produce 1 , 3 bisphosphoglycerate to produce one molecule of NADH in the presence of the enzyme GA3P dehydrogenase .

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92 - alcoholic fermentation results in the regenration of NAD + along with the conversion of pyruvate to _______ and CO2 .

answer is ethanol.

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93 - the deficiency of which vitamine results in a condition called beri beri ?

thiamine is the answer .

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94 - transketolase has a thiamine pyrophosphate cofactor and catalyses the transfer of a c2 unit from XU5P to R5P .

true .

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95 - the three products of glycolysis are ATP , NADH and pyruvate .

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96 - what does ATP do to PFK , at high concentrations?

- it acts as an allosteric inhibitor , by binding to the T state .

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97 - the level of available ______, regulates hemoglobin's oxygen affinity ?

answer is 2 ,3 BPG.


TO READ COMPLETELY ABOUT GLYCOLYSIS CLICK HERE

TO KNOW MORE ABOUT HMP SHUNT CLICK HERE

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11 - biochemistry mcqs - 76 to 86 - glycolysis

76 - an enzyme that transfers phosphoryl groups between ATP and a metabolite ?

a- kinase
b- aldolase
c- enolase
d- mutase

answer is a .


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77 - the ion essential for kinase activity ?

answer - magnesium .

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78 - the enzyme which catalyses the transfer of a functional group from one position to other ?

a- mutase
b- enolase
c- aldolase
d- kinase

answer is a . mutase . phosphoglycero mutase converts the 3 phosphoglycerate to 2 phosphoglycerate .


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79 - compounds with high phosphoryl group transfer potentials are formed during glycolysis .

the above statement is true .

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80 - when the need for ribose 5 phosphate exceeds that of NADPH , reversal of the transaldolase and transketolase reactions , diverts ribose 5 phosphate from the glycolytic pathway .

the above statement is true .

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81 - after phosphorylation , galactose reacts with the UDPG to form glucose 1 phosphate and ___________ before an epimerization reaction ?

answer is UDP - GALACTOSE

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82 - fructose metabolism in muscle requires only one step before it can enter into glycolysis ?

the above statement is true .

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83 - it has been demonstrated that triose phosphate isomerase has a reaction rate that is diffusion controlled and is therefore an example an enzyme that has reached catalytic perfection ?

the above statement is true .

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84 - enolase catalyses a reaction that results in the formation of a high energy intermediate .

the above statement is true . the enzyme enolase catalyses the conversion of the 2 - phosphoglycerate to phosphoenolpyruvate .

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85 - the statement which describes glycolysis stage II , the stage of energy recovery are ?

answer is --- two molecules of glyceraldehyde 3 phosphate are converted to pyruvate and four molecules of ATP are generated .

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86 - ribulose 5 phosphate is converted to xylulose 5 phosphate by the action of the enzyme ?

a- isomerase
b- epimerase
c- kinase
d- aldolase

answer is b .

TO READ COMPLETELY ABOUT GLYCOLYSIS CLICK HERE

TO KNOW MORE ABOUT HMP SHUNT CLICK HERE

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10 - HMP shunt or pentose phosphate pathway

CLICK ON THE IMAGE FOR A BIGGER IMAGE .

The main purpose of the pentose phosphate pathway is to regenerate NADPH from NADP⁺ through an oxidation/ reduction reaction. This reaction is coupled to the formation of ribose 5-phosphate from glucose 6-phosphate. NADPH is used for reductive reactions in anabolism, especially in fatty acid synthesis. In red blood cells, the major role of NADPH is to reduce the disulfide form of glutathione to the sulfhydryl form. The reduced glutathione is pertinent for maintaining the normal structure of red blood cells and for keeping hemoglobin in the ferrous state [Fe(II)]. The nonoxidative portion of the pathway creates carbon chain molecules ranging from 3 to 7 carbons. These compounds are intermediates in glycolysis and gluconeogenesis or other biosynthetic processes. The pentose phosphate pathway primarily produces NADPH, ribose 5-phosphate, fructose 6-phosphate, and glyceraldehyde 3-phosphate.

9 - biochemistry mcqs - 65 to 75 - glycolysis

65 - which enzyme is the major control point for glycolysis in muscle under most conditions .

a- glucokinase
b- hexokinase
c- phosphofructokinase
d- pyruvate kinase

answer is c .

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66 - ATP in fast twitch muscle fibres is supplied predominantly by which type of glycolysis

a- aerobic
b- anaerobic

answer is b . anaerobic glycolysis .

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67 - the rate of ATP production by anaerobic glycolysis can be upto 100 times faster than that of oxidative phosphorylation .

the above statement is true .

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68 - under which conditions is the complete oxidation of pyruvate mediated by citric acid cycle ?

a- aerobic
b- anaerobic

answer is a .

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69 - impaired substrate cycling may lead to a lack of nonshivering thermogenesis and result in cold sensitivity in obese individuals .

the above statement is true .

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70 - which molecule acts as a signal amplifier when concentrations of ATP are low to increase the phosphofructokinase activity ?

a- ADP
b- ATP
c- AMP
d- NADH

answer is c . AMP .

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71 - Ribulose 5 phosphate ( RU5P ) is converted to ribose 5 phosphate ( R5P ) by the enzyme ?

a- ribulose 5 phosphate dehydrogenase
b- ribose 5 phosphate dehydrogenase
c- RU5P ISOMERASE
d- R5P ISOMERASE

the answer is C .

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72 - which aminoacid side chain forms the schiff base with the substrate in the aldolase reaction ?

a- arginine
b- serine
c- tyrosine
d- lysine

answer is d.

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73 - lactate formed in skeletal muscle cells during anaerobic glycolysis is carried back to the liver , where it is used to synthesize

a- glucose
b- fructose
c- fatty acids
d- amino acids

answer is a .

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74 - flouride ion inhibits glycolysis by inhibiting the action of which enzyme ?

answer - enolase
aldolase

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75 - what is the enzyme which catalyses the formation of glyceraldehyde 3 phosphate and dihydroxy acetone phosphate ?

a- aldolase
b- enolase
c- kinase
d- mutase

answer is a . aldolase .


TO READ COMPLETELY ABOUT GLYCOLYSIS CLICK HERE

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8 - biochemistry mcqs - 54 to 64 - glycolysis

54- in glycolysis ?

ans- glucose is converted inot 2 molecules of pyruvate by the synthesis of two NADH and 2 ATP molecules and utilisation of 2ATP molecules too .

- i dont wanna give u choices in this question because it confuses u a lot , so stick to the above statement .

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55 - the compound which reduces the affinity of pyruvate kinase for its substrate ?

a- phosphoenol pyruvate
b- pyruvate
c- NADH
d- ATP

answer is ATP .

The pyruvate kinase converts phosphoenol pyruvate to pyruvate and in this reaction ATP is synthesized .

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56 - in muscle , glycolytic flux is subject to regulation by substrate cycling .

the above statement is true .

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57 - a deficiency of type B aldolase , results in __________ intolerance , a self limiting genetic disease ?

a- fructose intolerance
b- glucose intolerance
c- galactose intolerance
d- ribose intolerance

the answer is a .

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58 - the isomerisation of glucose-6-phosphate to fructose-6-phosphate is catalysed by which enzyme ?

a- hexokinase
b- glucokinase
c- phosphoglucose isomerase
d- phosphofructo kinase

answer is c . phosphoglucose isomerase.

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59 - the glyceraldehyde 3 phosphate dehydrogenase reaction is exergonic and will therefore proceed in the forward direction ?

the above statement is false . the glyceraldehyde 3 phosphate dehydrogenase reaction is slightly endergonic , but is pulled forward by the subsequent reaction of phosphoglycerate kinase . phosphoglycerate kinase converts 1 , 3 bisphosphoglycerate to 3 phosphoglycerate .

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60 - the rate of NADPH production is controlled by the rate of glucose-6-phosphate dehydrogenase reaction .

the above statement is true .

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61 - the exclusion of water from the active site of hexokinase is responsible for preventing the hydrolysis of ATP from being the dominant reaction during catalysis .

the above statement is true .

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62 - phosphoglycerate kinase catalyses a step in glycolysis , which results in the formation of ATP .

the above statement is true . the enzyme phosphoglycerate kinase catalyses the conversion of 1 , 3 bisphosphoglycerate to 3 phosphoglycerate to produce one ATP .

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63 - The hexokinase has very low affinity for hexoses .

the statement is true .

---------------------------------------------------------

64 - in two steps mannose is converted to ______, to enter into the glycolytic pathway ?

a- fructose 6 phosphate
b- glucose 6 phosphate
c- fructose
d- glucose

answer is a .


TO READ COMPLETELY ABOUT GLYCOLYSIS CLICK HERE

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7 - glycolysis

Glycolysis is the sequence of reactions that converts glucose into pyruvate with the concomitant production of a relatively small amount of adenosine triphosphate (ATP). The word is derived from Greek γλυκύς (sweet) and λύσις (letting loose).

It is the initial process of most carbohydrate catabolism, and it serves three principal functions:

1. The generation of high-energy molecules (ATP and NADH) as cellular energy sources as part of aerobic respiration and anaerobic respiration; that is, in the former process, oxygen is present, and, in the latter, oxygen is not present
2. Production of pyruvate for the citric acid cycle as part of aerobic respiration
3. The production of a variety of six- and three-carbon intermediate compounds, which may be removed at various steps in the process for other cellular purposes.

As the foundation of both aerobic and anaerobic respiration, glycolysis is the archetype of universal metabolic processes known and occurring (with variations) in many types of cells in nearly all organisms. Glycolysis, through anaerobic respiration, is the main energy source in many prokaryotes, eukaryotic cells devoid of mitochondria (e.g., mature erythrocytes) and eukaryotic cells under low-oxygen conditions (e.g., heavily-exercising muscle or fermenting yeast).

In eukaryotes and prokaryotes, glycolysis takes place within the cytosol of the cell. In plant cells, some of the glycolytic reactions are also found in the Calvin-Benson cycle, which functions inside the chloroplasts. The wide conservation includes the most phylogenetically deep-rooted extant organisms, and thus it is considered to be one of the most ancient metabolic pathways.

The most common and well-known type of glycolysis is the Embden-Meyerhof pathway, initially explained by Gustav Embden and Otto Meyerhof. The term can be taken to include alternative pathways, such as the Entner-Doudoroff Pathway. However, glycolysis will be used here as a synonym for the Embden-Meyerhof pathway.

6 - biochemistry mcqs - 41 to 53 - citric acid cycle

41 - the most crucial regulators of the citric acid cycle are its substrates , acetyl co A and oxaloacetate , and its product , NADH .

the above statement is true .

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42 - which enzyme of the citric acid cycle is very similar structurally and mechanistically to lactate dehydrogenase and alcohol dehydrogenase ?

a- alpha ketoglutarate dehydrogenase
b- succinate dehydrogenase
c- NAD + dependent isocitrate dehydrogenase
d- malate dehydrogenase

answer is d .

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43 - the thiamine pyrophosphate ( TPP ) a cofactor is bound to E1 and decarboxylates pyruvate , yielding a hydroxyethyl TPP carbon ion .

the above statement is true .

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44 - several biosynthetic pathways use citric acid cycle intermediates as starting material for anabolic reactions .

the above statement is true .

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45 - lipoamide consists of lipoic acid covalently joined to the epsilon - amino group of a lysine residue via an amide bond .

the above statement is true .

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46 - how is flux through out the citric acid controlled ?

a- primarily by control of citrate synthase
b- primarily by control of isocitrate dehydrogenase
c- primarily by control of alpha ketoglutarate dehydrogenase
d- at many points , including all the above

answer is d .

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47 - alpha ketoglutarate dehydrogenase is a multienzyme complex containing alpha ketoglutarate dehydrogenase ( E 1 ) , dihydro lipoyl trans succinylase ( E2 ) and dihydro lipoyl dehydrogenase .

the above statement is true .

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48 - in pyruvate dehydrogenase which cofactor is used to decarboxylate pyruvate?

a- TPP
b- lipoic acid
c- co A
d- FAD

the answer is a .

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49 - describe the regulatio of the conversion of isocitrate to alpha keto glutarate ?

a- calcium and ADP stimulate , NADH AND ATP inhibit .

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50 - Isocitrate lyase and malate sythase occur in both plants and animals .

the above statement is false . these enzymes occur only in plants .

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51 - acetyl co A is formed from pyruvate through oxidative decarboxylation by a multienzyme complex named ?

answer is pyruvate dehydrogenase .

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52 - which three compounds associated with the citric acid cycle inhibit their own synthesis ?

answer is acetyl co A , citrate and succinyl co A .

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53 - the tight coupling of oxygen consumption , NADH reoxidation and ATP production in the citric acid cycle requires regulation by feedback mechanisms that coordinate NADH Production with energy expenditure .

true.

TO VIEW THE CITRIC ACID CYCLE CLICK HERE

5 - biochemistry mcqs - 31 to 40 - citric acid cycle

31 - for every NADH that passes its electrons on to the electron transport chain , approximately how many ATP are produced from the ADP and phosphate ?

answer is 3.

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32 - isocitrate lyase cleaves isocitrate to succinate and __________ in the glyoxylate pathway ?

answer is glyoxylate .

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33 - in a net reaction of the citric acid cycle , what are the reactants ?

answer is ---------- 3 NAD + plus FAD plus GDP plus PHOSPHATE plus acetyl co A .

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34 - which segment of the citric acid cycle is used in the glyoxylate pathway ?

answer is succinate to oxaloacetate .

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35 - gluconeogenesis takes place in the cytosol and the oxaloacetate must be converted for transport out of the mitochondrion .

the above statement is true .

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36 - which substrate in the citric acid cycle is coupled to the reduction of FAD to FADH2 ?

a- citrate
b- isocitrate
c- succinate
d- fumarate

answer is c .

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37 - which enzyme complex of e coli is a particle of about 4600 kD , with a diameter of 300 .

answer is pyruvate dehydrogenase .

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38 - when glucose is converted to lactate or ethanol , a relatively reduced product leaves the cell.

the above statement is true .

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39 - albert szent - gyorgyi found that cellular respiration is dramatically decreased by small amounts of succinate , fumarate , malate or oxaloacetate .

the above statement is false . the cellular respiration actually increases after adding these compounds .

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40 - the biosynthesis of which compounds uses the alpha ketoglutarate and oxaloacetate as starting materials ?

answer is amino acid biosynthesis .


TO VIEW THE CITRIC ACID CYCLE CLICK HERE

4 - biochemistry mcqs - 21 to 30 - citric acid cycle

21 - the enzyme of the citric acid cycle that is inhibited by NADH ?

Answer is citrate synthase .

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22 - which citric acid cycle intermediates can be used for the synthesis of amino acids and can be regenerated by the same amino acids ?

a- succinyl co A and succinate
b- succinate and fumarate
c- malate and oxaloacetate
d- alpha ketogluatarate and oxaloacetate .

the correct answer is d . alpha ketoglutarate and oxaloacetate .

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23 - what is formed in a second concerted acid - base catalysed step of citrate synthase , in which the acetyl co A enol attacks oxaloacetate ?

answer is citryl co A .

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24 - which is the thiamine pyro phosphate requiring enzyme that decarboxylates pyruvate with the formation of a hydroxyethyl - TPP intermediate ?

answer is pyruvate dehydrogenase .

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25 - what is the name of the catalytically inactive E2 like protein existing in six copies that may help bind E3 to the complex .

answer is PROTEIN X .

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26 - What is the name of the cofactor that is bound to E3 and is reduced by lipoamide?

answer is FAD.

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27 - this cofactor accepts the acetyl group from the lipoamide in the pyruvate dehydrogenase complex ?

answer is coenzyme A .

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28 - This reaction is catalysed by E 3 , in which an acetyl group is transfered to co A , yielding acetyl co A and dihydrolipoamide E2 .

answer is TRANSESTERIFICATION .

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29 - Oxaloacetate undergoes transamination with alanine to produce what ?

a- glutamate and pyruvate
b- glutamate and alpha keto glutarate
c- aspartate and pyruvate
d- aspartate and alpha ketoglutarate

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30 - which enzyme produces the second CO 2 and NADH of the citric acid cycle ?

answer is alpha ketoglutarate dehydrogenase .

TO VIEW THE CITRIC ACID CYCLE CLICK HERE

3 - biochemistry mcqs - 11 to 20 - citric acid cycle

11 - citrate has the ability to inhibit this enzyme by competing with oxaloacetate ?

answer is CITRATE SYNTHASE .

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12 - The molecule which inhibits isocitrate dehydrogenase ?

answer is CALCIUM . Ca +2.

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13 - this molecule regulates the citric acid cycle at many points , including the activation of pyruvate dehydrogenase phosphatase , isocitrate dehydrogenase and alpha ketoglutarate dehydrogenase .

answer is SERINE .

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14 - In e coli , this enzyme is inactivated by the phosphorylation of a serine residue in the active site ?

answer is isocitrate dehydrogenase .

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15 - covalent modification of E 1 occurs by the specific phosphorylation of WHICH residue in a reaction catalysed by pyruvate dehydrogenase kinase ?

answer is ATP .

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16 - various dicarboxylates ( alpha ketoglutarate , succinate and malate ) and a tricarboxylate ( citrate ) are rapidly oxidised by muscle tissue during respiration.

this statement is true .

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17 - which citric acid cycle intermediate can be used for the synthesis of porphyrins ?

a - succinate
b- succinyl co A
c- fumarate
d- malate

answer is b .

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18 - which possess the enzymes that mediate the net conversion of acetyl co A to oxaloacetate , which can be used for gluconeogenesis .

answer is PLANTS OR GLYOXYSOMES .

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19 - Which is the cofactor that is the substrate for E 3 and is reduced by FADH2?

Answer is NAD+

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20 - The citric acid cycle acts as a multistep catalyst that can oxidize an unlimited number of ______ groups ?

answer is acetyl groups .

TO VIEW THE CITRIC ACID CYCLE CLICK HERE

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2 - biochemistry mcqs - 1 to 10 - citric acid cycle

1 - for every FADH2 synthesised by the citric acid cycle , approximately how many number of ATP are produced from the ADP AND PHOSPHATE ?

answer is two .

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2 - which substrates in the citric acid cycle are coupled to the production of NADH ?

answers are ISOCITRATE , ALPHA KETOGLUTARATE AND MALATE .

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3 - the citric acid cycle oxidises the acetyl group of acetyl coA to how many molecules of CO2?

answer is 2 . one molecule of CO2 during the conversion of the isocitrate to alpha ketoglutarate in the presence of the enzyme isocitrate dehydrogenase , and the other during the conversion of the alpha keto glutarate to succinyl co A in the presence of the enzyme alpha keto glutarate dehydrogenase .

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4 - the enzyme which couples the cleavage of the high energy succinyl co-A to the synthesis of a high energy nucleoside triphosphate is ?

answer is SUCCINYL CO A SYNTHETASE .

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5 - the enzyme which catalyses the final reaction of the citric acid cycle regenerating the oxaloacetate is ?

answer is MALATE DEHYDROGENASE .

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6 - The enzyme which catalyses the hydration of a double bond of fumarate to form malate ?

answer is fumarase .

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7 - the enzyme which catalyses the stereospecific dehydrogenation of succinate to fumarate ?

answer is SUCCINATE DEHYDROGENASE.

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8 - in eukaryotes , all the enzymes for the citric acid cycle are located in the ?

answer is MITOCHONDRION .

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9 - lipoyllysyl arm acts as a long tether that swings the disulfide group from E1 to the E 2 active site , and finally to E 3 , where the oxidised disulfide is reduced .

the above statement is FALSE .The reduced disulfide at E3 is reoxidised .

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10 - in addition to pyruvate what are the two additional sources of acetyl co A ?

a- glucose and amino acids
b- amino acids and fatty acids
c- amino acids and glucose
d- glycogen and fatty acids

answer is B . amino acids and fatty acids .

TO VIEW THE CITRIC ACID CYCLE CLICK HERE

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1- citric acid cycle

click on this image for a beautiful large image .

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Fig. 1: The Citric Acid Cycle
(Also Known as the Tricarboxylic Acid Cycle and the Krebs Cycle)

1. Before the pyruvates from glycolysis can feed into the citric acid cycle, they must undergo a transition reaction. The pyruvate is converted into a 2-carbon acetyl group as the third carbon is lost as CO₂. The acetyl group is attached to coenzyme A to form acetyl-CoA.
2. The 2-carbon acetyl-CoA combines with the 4-carbon oxaloacetate of the citric acid cycle to form 6-carbon citrate.
3. Citrate is converted to isocitrate.
4. The 6-carbon isocitrate is oxidized by NAD⁺ to produce reduced NADH and 5-carbon alpha-ketoglutarate. (One carbon is lost as CO₂.)
5. The 5-carbon alpha-ketoglutarate is oxidized by NAD⁺ to produce reduced NADH and 4-carbon succinyl-CoA. (One carbon is lost as CO₂.)
6. Oxidation of succinyl-CoA produces succinate and one GTP that is converted to ATP.
7. Oxidation of succinate by FAD produces reduced FADH₂ and fumarate.
8. Fumarate is converted into malate.
9. Oxidation of malate by NAD⁺ produces reduced NADH and oxaloacetate.

The two molecules of acetyl-CoA from the transition reaction enter the citric acid cycle. This results in the formation of 6 molecules of NADH, two molecules of FADH2, two molecules of ATP, and four molecules of CO2. The NADH and FADH2 molecules then carry electrons to the electron transport system for further production of ATPs by oxidative phosphorylation.