Category: Biochemistry Objective Questions

Biochemistry Multiple Choice Questions on “Phosphoryl Group Transfers and ATP”.

1. Anabolism and catabolism are chemically linked in the form of __________
A. ADP
B. ATP
C. Phosphodiester linkage
D. ASP
Answer: B
Clarification: Anabolism is an energy intake process where small molecules build upto large molecules whereas catabolism involves the release of energy where large molecules tear down to smaller molecules.

2. Which of the following statements is false about ATP hydrolysis?
A. It is highly exergonic
B. Activation energy is relatively high
C. ∆G^‘°=-30.5kJ/mol
D. ∆G^‘°=30.5kJ/mol
Answer: D
Clarification: ∆G^‘° should be negative for an exergonic process.

3. An endergonic reaction ____________
A. Proceeds spontaneously
B. Does not require activation energy
C. Releases energy
D. Requires energy
Answer: D
Clarification: Endergonic reaction involves intake of energy.

4. An exergonic reaction ____________
A. Proceeds spontaneously
B. Does not require activation energy
C. Releases energy
D. Requires energy
Answer: C
Clarification: Exergonic reaction involves release of energy.

5. Phosphoryl groups are derivatives of ____________
A. Phosphorous acid
B. Phosphoric acid
C. Acetic acid
D. Citric acid
Answer: B
Clarification: Phosphoryl groups are derivatives of phosphoric acid.

6. Water does a nucleophilic attack on phosphate monoester by producing ____________
A. Phosphorous chloride
B. Phosphorous sulfide
C. Inorganic phosphate
D. Organic phosphate
Answer: C
Clarification: Inorganic phosphate is produced when a nucleophilic attack is done by water on phosphate monoester.

7. The phosphate groups used during glycolysis are ____________
A. Organic
B. Inorganic
C. Neutral
D. None
Answer: B
Clarification: Phosphorous can only be produced from inorganic phosphate.

8. Which of the following is false about acetyl-coA?
A. It is a thioester
B. It has a large, negative standard free energy of hydrolysis
C. It contains phosphorous atom in the position occupied by an oxygen atom in oxygen esters
D. It contains a sulfur atom in the position occupied by an oxygen tom in oxygen esters
Answer: C
Clarification: Acetyl-coA is a thioester containing phosphorous atom in the position occupied by an oxygen atom in oxygen esters.

9. Which is an example of chemical to osmotic energy conversion that occurs in living organisms?
A. ATP-driven muscle contraction
B. ATP-dependent photon emission in fireflies
C. light-induced electron flow in chloroplasts
D. ATP-driven active transport across a membrane
Answer: D
Clarification: ATP-driven muscle contraction is an example for chemical to mechanical energy conversion.
ATP-dependent photon emission in fireflies is an example for chemical to electromagnetic energy conversion.
Light-induced electron flow in chloroplasts is an example for electromagnetic to electrical energy conversion.

10. Which is an example of chemical to electromagnetic energy conversion that occurs in living organisms?
A. ATP-driven muscle contraction
B. ATP-dependent photon emission in fireflies
C. light-induced electron flow in chloroplasts
D. ATP-driven active transport across a membrane
Answer: B
Clarification: ATP-driven muscle contraction is an example for chemical to mechanical energy conversion.
Light-induced electron flow in chloroplasts is an example for electromagnetic to electrical energy conversion.
ATP-driven active transport across a membrane is an example for chemical to osmotic energy conversion.

11. Which is an example of chemical to mechanical energy conversion that occurs in living organisms?
A. ATP-driven muscle contraction
B. ATP-dependent photon emission in fireflies
C. light-induced electron flow in chloroplasts
D. ATP-driven active transport across a membrane
Answer: A
Clarification: ATP-dependent photon emission in fireflies is an example for chemical to electromagnetic energy conversion.
Light-induced electron flow in chloroplasts is an example for electromagnetic to electrical energy conversion.
ATP-driven active transport across a membrane is an example for chemical to osmotic energy conversion.

12. Which is an example of electromagnetic to electrical energy conversion that occurs in living organisms?
A. ATP-driven muscle contraction
B. ATP-dependent photon emission in fireflies
C. light-induced electron flow in chloroplasts
D. ATP-driven active transport across a membrane
Answer: C
Clarification: ATP-driven muscle contraction is an example for chemical to mechanical energy conversion.
ATP-dependent photon emission in fireflies is an example for chemical to electromagnetic energy conversion.
ATP-driven active transport across a membrane is an example for chemical to osmotic energy conversion.

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Biochemistry Multiple Choice Questions on “Lipids as Signals, Cofactors, and Pigments”.

1. Phosphorylation of phosphatidylinositol yields __________
A. Phosphatidylinositol 4, 5-biphosphate
B. Phosphatidylinositol 3, 5-biphosphate
C. Phosphatidylinositol 3, 4-biphosphate
D. Phosphatidylinositol 5, 6-biphosphate
Answer: A
Clarification: Phosphorylation of phosphatidylinositol yields phosphatidylinositol 4, 5-biphosphate.

2. Which of the following vitamin is derived from cholesterol?
A. A
B. B
C. C
D. D
Answer: D
Clarification: Vitamin-D is derived from cholesterol.

3. What leads to the activation of protein kinase C?
A. Release of intracellular Ca⁺² + diacylglycerol
B. Release of intracellular Mg+ + diacylglycerol
C. Release of intracellular Ca⁺² + glycerol
D. Release of intracellular Ca⁺² + triacylglycerol
Answer: A
Clarification: Release of intracellular Ca⁺² + diacylglycerol causes activation of protein kinase C.

4. Which of the following serves as a specific binding site for the proteins involved in membrane fusion during exocytosis?
A. Phosphatidylinositol
B. Phosphatidylinositol 4, 5-biphosphate
C. Phosphatidylinositol 3, 5-biphosphate
D. Phosphatidylinositol 3, 4-biphosphate
Answer: B
Clarification: Phosphatidylinositol 4, 5-biphosphate in the cytoplasmic face of plasma membranes serves as a specific binding site for certain cytoskeletal proteins and for some soluble proteins involved in membranes fusion during exocytosis.

5. Which of the following hormone is responsible for the activation of phospholipase C?
A. Serotonin
B. Cortisol
C. Vasopressin
D. Adrenaline
Answer: C
Clarification: Vasopressin, when it binds to the plasma membrane receptors on the epithelial cells of the renal collecting duct, a specific phospholipase C is activated.

6. An example of glycerophospholipid involved in cell signaling is __________
A. Cardiolipin
B. Phosphatidic acid
C. Phosphatidylcholine
D. Phosphatidylinositol
Answer: D
Clarification: Phosphatidylinositol is involved in cell signaling.

7. Which of the following type structure contains all the three glycosphingolipids?
A. B structure
B. A structure
C. O structure
D. AB structure
Answer: C
Clarification: Type O structure has all three glycosphingolipids.

8. The lipids with potent bio activities derived from isoprenoid precursors are common in __________
A. Vitamin A, K, ubiquinone and dolichol
B. Vitamin A, D, ubiquinone and dolichol
C. Vitamin A, B, D and K
D. Vitamin A, B, K and dolichol
Answer: A
Clarification: Vitamin A, K, ubiquinone and dolichol have in common the lipids with potent bio activities derived from isoprenoid precursors.

9. Which of the following vitamin is responsible for Ca⁺² and phosphate metabolism?
A. A
B. K
C. E
D. D
Answer: D
Clarification: Vitamin A –vision
Vitamin K-blood clotting
Vitamin E-prevention of oxidative damage.

10. How many products are obtained by the hydrolysis of phosphatidylinositol by phospholipase C?
A. 1
B. 2
C. 3
D. 4
Answer: B
Clarification: Inositol 1, 4, 5-triphosphate and diacylglycerol are the two products obtained by the hydrolysis of phosphatidylinositol by phospholipase C.

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Biochemistry Multiple Choice Questions on “Examples Of Enzymatic actions”.

1. By what factor chymotrypsin enhances the rate of peptide bond hydrolysis?
A. 10⁷
B. 10⁸
C. At least 10⁹
D. 10⁶
Answer: C
Clarification: Chymotrypsin enhances the rate of peptide bond hydrolysis by a factor of at least 10⁹.

2. The active site of chymotrypsin consists of a catalytic triad of which of the following amino acid residues?
A. Serine, histidine and aspartate
B. Serine, histidine and glutamate
C. Threonine, histidine and aspartate
D. Methionine, histidine and aspartate
Answer: A
Clarification: Aspartate holds the histidine side chain in the correct direction to accept proton from serine.

3. Which of the following statements are true about the reactions at the active center of chymotrypsin?
A. The aspartate residue gives an electron to histidine
B. The aspartate residue gives a proton to histidine
C. The aspartate residue keeps the histidine in the correct direction
D. A proton moves from the aspartate to serine to histidine in the catalytic triad of chymotrypsin
Answer: C
Clarification: Aspartate residue accepts a proton from serine.

4. The polypeptide chains in chymotrypsin are linked by ___________
A. Hydrogen bonds
B. Ionic bonds
C. Disulfide bond
D. SH-SH bond
Answer: C
Clarification: The protein consists of three polypeptide chains linked by disulfide bonds.

5. Which of the following is false about chymotrypsin?
A. Hydrolytic cleavage of a peptide bond by chymotrypsin has two phases
B. It is activated in the presence of trypsin
C. It is synthesized in the thyroid gland
D. Polypeptide chains in chymotrypsin are linked by S-S bonds
Answer: C
Clarification: Chymotrypsin is synthesized in the pancreas.

6. Which of the following is true about the structure of hexokinase?
A. U-shaped
B. T-shaped
C. E-shaped
D. G-shaped
Answer: A
Clarification: Hexokinase has a U-shaped structure.

7. Which of the following is true?
A. Xylose is stereo chemically similar to glucose but one carbon shorter
B. Xylose binds to hexokinase in a position where it can be phosphorylated
C. Addition of xylose increases the rate of ATP hydrolysis
D. The binding of xylose is sufficient to induce a change in hexokinase to its active conformation
Answer: B
Clarification: Xylose binds to hexokinase at a position where it cannot be phosphorylated.

8. Which of the following catalyzes the reversible degradation of 2-phosphoglycerate to phosphoenolpyruvate?
A. Chymotrypsin
B. Hexokinase
C. Enolase
D. Trypsin
Answer: C
Clarification: Enolase catalyzes the reversible degradation of 2-phosphoglycerate to phosphoenolpyruvate.

9. Which of the following catalyzes the reversible reaction of β-D-Glucose to glucose 6-phosphate?
A. Chymotrypsin
B. Hexokinase
C. Enolase
D. Trypsin
Answer: B
Clarification: Hexokinase catalyzes the reversible reaction of β-D-Glucose to glucose 6-phosphate.

10. Which of the following is false about lysozyme?
A. It is an antibacterial agent found in tears and egg white
B. The substrate of lysozyme is peptidoglycan
C. Lysozyme cleaves (β1 → 4) glycosidic C-O bonds between two types of sugar residue in the molecule NAM and NAG
D. It is a bisubstrate enzyme
Answer: D
Clarification: Hexokinase is the bisubstrate enzyme.

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Biochemistry Multiple Choice Questions on “Weak Interactions in Aqueous Systems”.

1. What makes water a liquid at room temperature?
A. Hydrogen bonds between water molecules
B. Covalent bonding
C. Noncovalent interactions
D. Van der Waals forces of attraction
Answer: A
Clarification: Hydrogen bonds between water molecules provide the cohesive forces that make water a liquid at room temperature.

2. ΔG is negative for which of the following processes?
A. Melting of ice and evaporation of water
B. Oxidation of nitrogen
C. Oxidation of gold
D. Burning of chlorine
Answer: A
Clarification: The Gibb’s free energy change (ΔG) must have a negative value for a process to occur spontaneously.
Melting of ice and evaporation of water are the two spontaneous processes at room temperature.

3. ΔH is positive for which of the following processes?
A. Oxidation of nitrogen
B. Melting of ice and evaporation of water
C. Oxidation of gold
D. Burning of chlorine
Answer: B
Clarification: Enthalpy change (ΔH) is positive for endothermic reactions, the reactions which involves absorption of energy.
Melting of ice and evaporation of water involves absorption of energy.

4. What is the factor that is responsible for salts like NaCl to dissolve in water easily?
A. Decrease in entropy
B. Increase in entropy
C. Increase in enthalpy
D. Decrease in enthalpy
Answer: B
Clarification: As a salt such as NaCl dissolves, the Na⁺ and Cl^– ions leaves the crystal lattice resulting in an increase in entropy(randomness) of the system which is largely responsible for the ease of dissolving salts such as NaCl in water.

5. What is the heat of vaporization of water?
A. 2260 J/g
B. 2260 kJ/g
C. 1260 J/g
D. 1260 kJ/g
Answer: A
Clarification: The amount of energy needed to change one gram of water to its vapor form at constant temperature is 2260 J/g.

6. The bond dissociation energy of hydrogen bonds in a water molecule is ______________
A. 470 kJ/mole
B. 470 J/mole
C. 23 kJ/mole
D. 23 J/mole
Answer: C
Clarification: The energy required to break the hydrogen bonds (H-H) in water molecule is 23 kJ/mole.

7. The bond dissociation energy of O-H bond in a water molecule is _____________
A. 23 kJ/mole
B. 470 kJ/mole
C. 470 J/mole
D. 23 J/mole
Answer: B
Clarification: The energy required to break O-H bond in a water molecule is more than that required for breaking hydrogen bond, which is 470 kJ/mole.

8. Which of the following is a hypertonic solution?
A. Oceans
B. Freshwater habitats
C. 0.45% sodium chloride
D. Red blood cells placed in fresh water
Answer: A
Clarification: The sea water or oceans are hypertonic to the extracellular fluid of many of the marine organisms. These marine organisms overcome the problem of hyper tonicity by expelling the salt water continuously.

9. Which of the following is a hypotonic solution?
A. 10% dextrose in water
B. 0.45% sodium chloride
C. 5% dextrose in 0.9% sodium chloride
D. Oceans
Answer: B
Clarification: 0.9% normal saline is isotonic and half of 0.9 = 0.45% makes the solution more diluted (contains more water), therefore the solution is hypotonic.

10. Which of the following is an isotonic solution?
A. 0.9% sodium chloride
B. 0.45% sodium chloride
C. Oceans
D. 10% dextrose in water
Answer: A
Clarification: The normal saline solution, 0.9% NaCl has the same salt concentration as the surrounding blood cells.

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Biochemistry Multiple Choice Questions on “ATP Synthesis-1”.

1. Which of the following is the prosthetic group of NADH dehydrogenase?
A. NADH
B. FAD
C. NADPH
D. FMN
Answer: D
Clarification: NADH initially binds to complex I and transfers two electrons to the flavin mononucleotide (FMN) prosthetic group of the enzyme creating FMNH₂.

2. Effect of valinomycin on oxidative phosphorylation does not involve _____________
A. pH gradient across the inner mitochondrial membrane decreases
B. Rate of flow of electrons increases
C. Rate of oxygen consumption increases
D. Net yield of ATP decreases
Answer: A
Clarification: pH gradient does not decrease.

3. If mitochondria were blocked at the site of NADH oxidation and were treated with succinate as substrate, what would the P : O ratio is?
A. Same as that normally produced by succinate
B. One more than normally produced by succinate
C. One less than normally produced by succinate
D. Zero
Answer: A
Clarification: If mitochondria were blocked at the site of NADH oxidation and were treated with succinate as substrate, the P : O ratio is the same as that normally produced by succinate.

4. If 2, 4-dinitrophenol is added to tightly coupled mitochondria that are actively oxidizing succinate ____________
A. Electron flow will continue but ATP synthesis will not occur
B. Electron flow will continue but ATP synthesis will be increased
C. Electron flow will cease but ATP synthesis will continue
D. Both electron flow and ATP synthesis will be ceased
Answer: A
Clarification: Electron transfer is catalyzed from succinate or NADH to O₂ but no ATP synthesis is coupled to this respiration.

5. If the oxidative phosphorylation was uncoupled in the mitochondria then there is a/an ____________
A. Decreased concentration of ADP in the mitochondria
B. Decreased oxidative rate
C. Increased inorganic phosphate in the mitochondria
D. Decreased production of heat
Answer: C
Clarification: If the oxidative phosphorylation was uncoupled in the mitochondria then there is an increased inorganic phosphate in the mitochondria.

6. If rotenone is added to the mitochondrial electron transport chain then ____________
A. Succinate oxidation remains normal
B. P: O ratio of NADH is reduced from 3:1 to 2:1
C. Oxidative phosphorylation is uncoupled at site I
D. Rate of NADH oxidation is diminished to two-thirds of its initial value
Answer: A
Clarification: If rotenone is added to the mitochondrial electron transport chain succinate oxidation remains normal.

7. Which of the following takes place in substrate level phosphorylation?
A. Oxidation of one molecule of substrate is linked to synthesis of more than one ATP molecule
B. High energy intermediate compounds cannot be isolated
C. Only mitochondrial reactions participate in ATP formation
D. Substrate reacts to form a product containing a high energy bond
Answer: D
Clarification: Substrate reacts to form a product containing a high energy bond.

8. Chemiosmotic hypothesis does not involve ____________
A. Only proton transport is strictly regulated, other positively charged ions can diffuse freely across the mitochondrial membrane
B. ATPase activity is reversible
C. Proton flow into the mitochondria depends on the presence of ADP and Pi
D. Electron transport by the respiratory chain pumps protons out of the mitochondria
Answer: A
Clarification: Not only proton transport but there is electron transport also.

9. Which one of the following is the one having highest redox potential?
A. Ubiquinone
B. O₂
C. FMN
D. NAD
Answer: B
Clarification: O₂ has the highest redox potential.

10. Which of the following accepts only one electron?
A. Cytochrome b
B. Coenzyme Q
C. FMN
D. FAD
Answer: A
Clarification: Cytochrome b accepts only one electron.

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Biochemistry Multiple Choice Questions on “Bioenergetics and Thermodynamics”.

1. If enthalpy change for a reaction is zero, then ∆G° equals to _____________
A. -T∆S°
B. T∆S°
C. -∆H°
D. lnk_eq
Answer: A
Clarification: From the equation, ∆G° = ∆H°-T∆S°
If ∆H° = 0 then ∆G° = -T∆S°.

2. ∆G° is defined as the ____________
A. Residual energy present in the reactants at equilibrium
B. Residual energy present in the products at equilibrium
C. Difference in the residual energy of reactants and products at equilibrium
D. Energy required in converting one mole of reactants to one mole of products
Answer: D
Clarification: ∆G° is defined as the energy required in converting one mole of reactants to one mole of products.

3. For a reaction if ∆G° is positive, then ____________
A. The products will be favored
B. The reactants will be favored
C. The concentration of the reactants and products will be equal
D. All of the reactant will be converted to products
Answer: B
Clarification: If ∆G° is negative, products are favored.

4. Unfolding of regular secondary protein structure causes ____________
A. Large decrease in the entropy of the protein
B. Little increase in the entropy of protein
C. No change in the entropy of the protein
D. Large increase in the entropy of the protein
Answer: D
Clarification: Entropy increases on a larger scale when unfolding of secondary protein structure takes place.

5. The study of energy relationships and conversions in biological systems is called as ____________
A. Biophysics
B. Biotechnology
C. Bioenergetics
D. Microbiology
Answer: C
Clarification: Bioenergetics is the study of energy relationships and conversions in biological systems.

6. The relationship between K^‘_eq and ∆G^‘° is?
A. ∆G^‘° = RTlnK^‘_eq
B. ∆G^‘° = -RTK^‘_eq
C. ∆G^‘° = RK^‘_eq
D. ∆G^‘° = -RK^‘_eq
Answer: B
Clarification: If the system is in equilibrium ∆G° = 0 and ∆G^‘° = -RTK^‘_eq is the correct relation between K^‘_eq and ∆G^‘°.

7. What does first law of thermodynamics state?
A. Energy can neither be destroyed nor created
B. Energy cannot be 100 percent efficiently transformed from one type to another
C. All living organisms are composed of cells
D. Input of heat energy increases the rate of movement of atoms and molecules
Answer: A
Clarification: First law of thermodynamics can also be termed as law of conservation of energy which states that energy can neither be destroyed nor created but can be transformed from one form of energy to another.

8. If ∆G^‘° of the reaction A → B is -40kJ/mol under standard conditions then the reaction ____________
A. Will never reach equilibrium
B. Will not occur spontaneously
C. Will proceed at a rapid rate
D. Will proceed from left to right spontaneously
Answer: D
Clarification: If ∆G^‘° < 0, reaction proceeds from left to right that means products are favored.

9. What is the relationship between ∆G and ∆G^‘°?
A. ∆G = ∆G^‘° + RTln([products]/[reactants])
B. ∆G = ∆G^‘° – RTln([products]/[reactants])
C. ∆G = ∆G^‘° + RTln([reactants]/[products])
D. ∆G = ∆G^‘° – RTln([reactants]/[products])
Answer: A
Clarification: ∆G = ∆G^‘° + RTln([products]/[reactants] ) is the correct relation between ∆G and ∆G^‘°.

10. Which of the following statements is false?
A. The reaction tends to go in the forward direction if ∆G is large and positive
B. The reaction tends to move in the backward direction if ∆G is large and negative
C. The system is at equilibrium if ∆G = 0
D. The reaction tends to move in the backward direction if ∆G is large and positive
Answer: D
Clarification: The reaction tends to move in the backward direction if ∆G is large and negative.

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