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Biochemistry MCQs Exam 2- PMU 2nd Year

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Biochemistry Exam 2- PMU 2nd Year
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Pregunta 1

Pregunta
The enzymes that catalyze oxidation and reduction reactions belong to class 1- oxidoreductases. Which are the subclasses of this class
Respuesta
  • oxidases
  • hydrolases
  • hydroperoxidases
  • oxygenases
  • transferases
  • dehydrogenases

Pregunta 2

Pregunta
Which enzymes play major role in the formation of energy in the respiratory chain:
Respuesta
  • dehydrogenases
  • oxidases
  • oxygenases
  • lyases
  • ligases

Pregunta 3

Pregunta
Which of the following vitamins is not part of the multienzyme pyruvate dehydrogenase (PDH) complex?
Respuesta
  • lipoic acid
  • thiamine
  • biotin
  • niacin
  • riboflavin

Pregunta 4

Pregunta
Which of the following is TRUE:
Respuesta
  • PDH is active in its dephospho form
  • PDH is inhibited by increased [NADH]/[NAD+] ratio
  • PDH is inhibited by increased [ATP]/ [ADP] ratio
  • PDH is activated by its product acetyl-CoA

Pregunta 5

Pregunta
Which of the following is TRUE:
Respuesta
  • the respiratory chain is localized in the inner mitochondrial membrane
  • the respiratory chain is localized in the cytosol
  • the respiratory chain generates energy (ATP) from the oxidation of the major foodstuffs: fats, carbohydrates, amino acids
  • the respiratory chain consists of four protein complexes embedded in the inner mitochondrial membrane

Pregunta 6

Pregunta
Which of the following redox systems are not part of the respiratory chain:
Respuesta
  • CoQ/CoQ H2
  • NAD+/NADH
  • cyt. P450
  • cyt.c (Fe2+)/cyt.c (Fe3+)
  • FAD/FADH2

Pregunta 7

Pregunta
Which of the following enzymes catalyze the reduction of O2 to H2O
Respuesta
  • NADH- CoQ oxidoreductase
  • CoQ- cyt c oxidoreductase
  • cyt c oxidase
  • ATP synthase

Pregunta 8

Pregunta
Which of the following drugs and chemicals inhibit the electron transport in the respiratory chain:
Respuesta
  • Barbiturates
  • Antimycin A
  • CO
  • CN- (cyanide)
  • Rotenone
  • Oligomycin

Pregunta 9

Pregunta
Which of the following about ATP synthase is TRUE:
Respuesta
  • ATP synthase is embedded in the inner mitochondrial membrane, together with the other respiratory chain complexes
  • ATP synthase is located in the intermembrane space
  • The enzyme complex consists of F1 and F2 subcomplexes
  • Be flow of protons through ATP synthase causes the production of ATP

Pregunta 10

Pregunta
Which of the following about citric acid cycle is TRUE:
Respuesta
  • The cycle occurs in the cytosol
  • The cycle occurs in the mitochondria
  • The citric acid cycle is the final step for oxidation of carbohydrates, lipids and proteins
  • NADH and FADH2 obtained in the cycle are oxidized in the respiratory chain and ATP is formed
  • The cycle occurs in the endoplasmic reticulum

Pregunta 11

Pregunta
Which of the following enzymes participate in citric acid cycle:
Respuesta
  • hexokinase
  • transketolase
  • citrate synthase
  • succinate dehydrogenase
  • pyruvate carboxylase

Pregunta 12

Pregunta
Which of the following drugs and chemicals act as inhibitors of the electron transport in the respiratory chain:
Respuesta
  • Rotenone
  • Barbiturates (e.g. amobarbital)
  • Oligomycin
  • CO and CN+

Pregunta 13

Pregunta
Which of the following about citric acid cycle is TRUE:
Respuesta
  • the initial reaction between acetyl-CoA and oxaloacetate to form citrate is catalyzed by aconitase
  • the α-ketoglutarate dehydrogenase complex requires the same cofactors as the PDH complex
  • succinate dehydrogenase contains FAD
  • as a result of the action of the dehydrogenases in the cycle 4 NADH and 1 FADH2 are produced per turn of the citric acid cycle

Pregunta 14

Pregunta
Which of the following metabolites are not intermediates of the citric acid acid cycle:
Respuesta
  • fumarate
  • succinyl-CoA
  • lactate
  • oxaloacetate
  • phosphoenolpyruvate

Pregunta 15

Pregunta
Which of the following about α-ketoglutarate dehydrogenase complex is TRUE:
Respuesta
  • it is inhibited by ATP, NADH, succinyl-CoA
  • it is activated by ATP, NADH, succinyl-CoA
  • it is activated by Ca2+
  • one of its cofactors lipoic acid

Pregunta 16

Pregunta
What is this?
Image:
5649ead3-4105-47e9-84e5-79f5f4f410e7 (image/png)
Respuesta
  • ATP

Pregunta 17

Pregunta
Which of the following cytochromes are not part of the mitochondrial respiratory chain:
Respuesta
  • cyt. P450
  • cyt. c1
  • cyt. c
  • cyt. b5
  • cyt, a

Pregunta 18

Pregunta
Which of the following statements about respiratory chains are true?
Respuesta
  • They are located in the inner mitochondrial membrane
  • They are located in the endoplasmic reticulum
  • They should be coupled with ATP synthase
  • Cyanides and CO can block forth complex of respiratory chain
  • Barbiturates can block second complex of respiratory chain

Pregunta 19

Pregunta
Which of the following about Krebs cycle are true?
Respuesta
  • It is a terminal common pathway for oxidation of all the substrates produced by the biological oxidation
  • Four metabolites from Krebs cycle donate H2 for the respiratory chains
  • Some of its metabolites can be used for biosynthesis
  • It can occur both in aerobic and anaerobic conditions

Pregunta 20

Pregunta
How many molecules of ATP will be provided by succinate dehydrogenase reaction from Krebs cycle?
Respuesta
  • 0
  • 1
  • 2
  • 3
  • 4

Pregunta 21

Pregunta
Examples of oxidative phosphorylation at substrate level are:
Respuesta
  • Isocitrate dehydrogenase reaction
  • Oxidative decarboxylation of α-ketoglutarate
  • Glyceraldehyde-3-phosphate dehydrogenase reaction
  • Malate dehydrogenase reaction
  • Enolase reaction

Pregunta 22

Pregunta
Which of the following statements oxidoreductases of biological oxidation are true?
Respuesta
  • They are always two-component enzymes
  • The Cofactor is always a redox system
  • They can be simple enzymes
  • Oxygenases are oxidoreductases
  • Dehydrogenases are oxidoreductases
  • Kinases are oxidoreductases

Pregunta 23

Pregunta
All the cytochromes contain as prosthetic group
Respuesta
  • NAD
  • FAD
  • Iron (Fe)- containing heme
  • Biotin
  • Vit. C

Pregunta 24

Pregunta
ADP/ATP system plays a key role in bioenergetics because:
Respuesta
  • ATP is the richest in energy compound
  • ATP can donate macroergic phosphoryl group to low-energy compounds and thus activate them
  • ADP can affect macroergic phosphoryl group from richer than ATP energy compunds
  • ATP has the middle position between the high and the low energy compounds according to the energy released during the hydrolysis of their bonds

Pregunta 25

Pregunta
Which of the following component of respiratory chain act as H+ pumps?
Respuesta
  • Cyt bc1 oxido-reductase
  • Cyt NADH- Co Q oxido-reductase
  • Cyt c oxidase
  • Succinate - Co Q. oxido-redudase

Pregunta 26

Pregunta
Which of the following statements about Pyruvate dehydrogenase complex are true
Respuesta
  • One of its enzymes is pyruvate carboxylase
  • One of its cofactors. is pyridoxal phosphate
  • It is active in its dephosphorylated form
  • It is located in the cytoplasm
  • It is an example of oxidative phosphorylation at substrate level

Pregunta 27

Pregunta
Which of the following act as uncouplers of the respiratory chain:
Respuesta
  • Barbiturates
  • Antimycin A
  • Oligomycin
  • Thyroid Hormones
  • 2.4-dinitrophenol

Pregunta 28

Pregunta
Which of the following about ATP synthase is TRUE:
Respuesta
  • ATP synthase is embedded in the inner mitochondrial membrane, together with the other respiratory chain complexes
  • ATP Synthase is located in the intermembrane space
  • The enzyme complex consists of F0 and F1 subcomplexes
  • The flow of protons through ATP synthase causes the production of ATP

Pregunta 29

Pregunta
Which of the following enzymes participate in citric acid cycle:
Respuesta
  • pyruvate kinase
  • succinate dehydrogenase
  • citrate synthase
  • fumarase
  • glucokinase

Pregunta 30

Pregunta
Which of the following about citric acid cycle represent its amphibolic role:
Respuesta
  • it provides substrates for gluconeogenesis
  • the citric acid cycle is only for oxidation of acetyl-CoA
  • it provides substrates for amino acids synthase
  • the citric acid cycle is the final step for oxidation of carbohydrates, lipids and proteins
  • it takes part in fatty acid synthesis

Pregunta 31

Pregunta
Which of the following are high energy compounds:
Respuesta
  • Creatine phosphate
  • GTP
  • Acetyl~CoA
  • Glucose-6-phosphate
  • Citrate

Pregunta 32

Pregunta
Which of the following vitamins is not part of the multi-enzyme pyruvate dehydrogenase (PDH) complex?
Respuesta
  • lipoic acid
  • thiamine
  • niacin
  • folic acid
  • riboflavin

Pregunta 33

Pregunta
What is this?
Image:
fdbb57d4-79a2-4694-9c8f-0f69840cf8c0 (image/jpeg)
Respuesta
  • Creatine Phosphate

Pregunta 34

Pregunta
Which of the following is TRUE:
Respuesta
  • the respiratory chain is localized in the inner mitochondrial membrane
  • the respiratory chain is localized in the endoplasmic reticulum
  • the respiratory chain generates energy (ATP) from the oxidization of the major foodstuffs: fats, carbohydrates, amino acids
  • one of the cytochromes in the respiratory chain is cyt. P450

Pregunta 35

Pregunta
Respiratory chain:
Respuesta
  • Can function only in aerobic conditions
  • Can function independently on the presence of oxygen
  • Is located in the inner mitochondria! membrane
  • Is located in the outer mitochondrial membrane
  • Is located in the mitochondrial matrix

Pregunta 36

Pregunta
Energy can be created in reactions catalyzed by:
Respuesta
  • Transferases
  • Lygases
  • Oxidoreductases
  • lsomerases

Pregunta 37

Pregunta
Oxidative phosphorylation:
Respuesta
  • Can be executed only at substrate level
  • Can be executed only in respiratory chains
  • Can be executed both at substrate level and in respiratory chains
  • Doesn't create energy
  • Is the process of accumulation energy in ATP-form at the expense of oxidation of a substrate

Pregunta 38

Pregunta
Which of the following statements about Pyruvate dehydrogenase complex are true?
Respuesta
  • It is composed of 3 enzymes, working together with 5 Cofactors
  • It located in the cytoplasm
  • ls one of the major donors of Acetyl Co A for Krebs cycle
  • ls activated by pyruvate, NAD and CoA, inhibited by NADH, and Acetyl Co A
  • ls regulated through reversible covalent modification

Pregunta 39

Pregunta
Which of the following about the processes of oxidation and reduction is true:
Respuesta
  • A chemical compound which is oxidized during the process of oxidation is known to be a reducer
  • A chemical compound which is oxidized during the process of oxidation is an oxidizer
  • A chemical compound which is reduced during the process of reduction is known to be a reducer
  • A chemical compound which is reduced during the process of reduction is known to be an oxidizer
  • Oxidation and reduction are coupled processes, mostly

Pregunta 40

Pregunta
Which of the following is low energy phosphate
Respuesta
  • Phosphoenolpyruvate
  • Creatine Phosphate
  • Glucose 6-phosphate
  • Fructose 6-phosphate
  • Glycerol 3-phosphate

Pregunta 41

Pregunta
Which of the following about FAD and FMN is true?
Respuesta
  • FAD and FMN are vitamin PP derivatives
  • FAD and FMN are vitamin B2 derivatives
  • FAD and FMN are vitamin B6 derivatives
  • FAD and FMN participate in bioenergetics as electron carriers
  • FAD and FMN are coenzymes of enzymes called dehydrogenase and oxidases mostly

Pregunta 42

Pregunta
Which of the following is true?
Respuesta
  • hydroperoxidases are two types of enzymes: peroxidases and catalase
  • hydroperoxidases use hydrogen peroxide as electron donor
  • hydroperoxidases contain NAD or NADP as coenzyme
  • hydroperoxidases contain FAD or FMN as coenzyme
  • hydroperoxidases contain heme or protoheme as coenzyme

Pregunta 43

Pregunta
How many molecules of ATP are synthesized in the citric acid cycle per turn?
Respuesta
  • 1
  • 6
  • 12
  • 36
  • 38

Pregunta 44

Pregunta
Complex 3 of the respiratory chain
Respuesta
  • accepts electrons and protons from coenzyme Q
  • is consisted of enzymes which operate with cytochromes as coenzymes
  • transfers electrons and protons from coenzyme Q to cytochrome C
  • transfers electrons and protons directly to oxygen
  • is "loaded" with electrons and protons from different substrates via NAD

Pregunta 45

Pregunta
How many molecules of NAD are reduced per turn in the citric acid cycle?
Respuesta
  • 1
  • 2
  • 3
  • 4
  • 5

Pregunta 46

Pregunta
Which of the following is true?
Respuesta
  • all enzymes of citric acid cycle are placed in mitochondria
  • there is an enzyme, involved in the citric acid cycle, which is anchored to the inner mitochondrial membrane
  • all enzymes of citric acid cycle are placed in cytosol
  • all enzymes of the citric acid cycle are place in the mitochondrial matrix
  • some of the enzymes of the citric acid cycle are places in the cytosol and other are placed in mitochondrion
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