Practice MCQs Flashcards by Josh Kelly

Which of the following is NOT a common way that electrons are transferred in biological systems?

A) Directly as free electrons
B) As hydrogen atoms
C) As molecular oxygen (O2)
D) As a hydride ion (H−)
E) Don’t know

C) As molecular oxygen (O2)

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NADH transfers electrons primarily via which mechanism?

A) Direct transfer of free electrons
B) Transfer as hydrogen atoms
C) Transfer as a hydride ion (H−)
D) Combination with molecular oxygen
E) Don’t know

C) Transfer as a hydride ion (H−)

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Which of the following statements about redox reactions in metabolism is TRUE?

A) FADH2 donates electrons by transferring a hydride ion
B) Oxygen acts as an electron donor in cellular respiration
C) NADH transfers electrons as a hydride ion (H−)
D) Electrons in metabolic pathways are transferred only through direct electron transfer
E) Don’t know

C) NADH transfers electrons as a hydride ion (H−)

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In which of the following metabolic reactions are electrons transferred as hydrogen atoms?

A) NADH → NAD+
B) FADH2 → FAD
C) Fe2 + 2+ → Fe3 + 3+
D) ATP hydrolysis
E) Don’t know

B) FADH2 → FAD

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Which metabolic pathway involves significant electron transfer via direct electron transfer?

A) Glycolysis
B) Electron Transport Chain
C) Citric Acid Cycle
D) Fatty Acid Beta-Oxidation
E) Don’t know

B) Electron Transport Chain

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Which vitamin is the precursor for NAD+ and NADP+?

A) Riboflavin (Vitamin B2)
B) Niacin (Vitamin B3)
C) Pantothenic acid (Vitamin B5)
D) Thiamine (Vitamin B1)
E) Don’t know

B) Niacin (Vitamin B3)

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What is the primary function of NAD+ in metabolism?

A) Transfer of acyl groups
B) Electron donation in anabolic reactions
C) Electron acceptance in catabolic reactions
D) Proton transport across membranes
E) Don’t know

C) Electron acceptance in catabolic reactions

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NADPH is primarily used in which type of metabolic reactions?

A) Catabolic reactions
B) Anabolic reactions
C) Electron transport chain
D) Protein synthesis
E) Don’t know

B) Anabolic reactions

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What is the structural difference between NAD+ and NADP+?

A) NADP+ has an additional phosphate group
B) NAD+ contains an extra ribose sugar
C) NADP+ has a flavin moiety
D) NAD+ and NADP+ are structurally identical
E) Don’t know

A) NADP+ has an additional phosphate group

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Which of the following correctly describes FAD and FMN?

A) They are derived from niacin
B) They are derived from riboflavin
C) They carry one electron at a time
D) They function as direct electron donors to cytochrome c
E) Don’t know

B) They are derived from riboflavin

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Which of the following statements about FAD and NAD+ is TRUE?

A) FAD can carry two electrons and two protons, whereas NAD+ carries only two electrons
B) FAD transfers electrons as a hydride ion, while NAD+ transfers electrons as free electrons
C) NAD+ is a stronger oxidizing agent than FAD
D) FAD functions only in catabolic reactions, while NAD+ functions only in anabolic reactions
E) Don’t know

A) FAD can carry two electrons and two protons, whereas NAD+ carries only two electrons

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What type of redox reactions involve FMN and FAD?

A) Two-electron hydride transfers
B) One- or two-electron transfers
C) Transfer of phosphate groups
D) Transfer of carbonyl groups
E) Don’t know

B) One- or two-electron transfers

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In the electron transport chain, which electron carrier directly donates electrons to complex II?

A) NADH
B) FMN
C) FADH2
D) Cytochrome c
E) Don’t know

C) FADH2

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Which cofactor is required for complex I (NADH dehydrogenase) in the electron transport chain?

A) FAD
B) FMN
C) Cytochrome c
D) Coenzyme Q
E) Don’t know

B) FMN

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Which statement best describes the role of NADPH in metabolism?

A) It donates electrons in oxidative phosphorylation
B) It provides reducing equivalents for biosynthesis
C) It transfers electrons directly to oxygen
D) It acts as an electron acceptor in glycolysis
E) Don’t know

B) It provides reducing equivalents for biosynthesis

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Which of the following coenzymes is derived from Vitamin B2 (Riboflavin)?

A) NAD+
B) FAD
C) Coenzyme A
D) Biocytin
E) Don’t know

B) FAD

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Which of the following correctly matches the coenzyme with its primary function?

A) NAD+ - Transfers CO₂
B) Coenzyme A - Transfers electrons
C) FAD - Transfers acyl groups
D) NAD+ - Transfers hydride ions
E) Don’t know

D) NAD+ - Transfers hydride ions

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Which coenzyme is involved in both electron transfer and acyl group transfer?

A) NAD+
B) Lipoate
C) Biocytin
D) PLP
E) Don’t know

B) Lipoate

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Which of the following coenzymes is involved in amino group transfer reactions?

A) TPP
B) PLP
C) FAD
D) NAD+
E) Don’t know

B) PLP

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What is the role of FAD in metabolism?

A) Transfers one electron at a time
B) Transfers two electrons as a hydride ion
C) Transfers acyl groups
D) Transfers CO₂ in carboxylation reactions
E) Don’t know

A) Transfers one electron at a time

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Which of the following statements is TRUE regarding NAD+ and NADP+?

A) NADP+ is primarily used in catabolic pathways
B) NAD+ primarily donates electrons in biosynthetic pathways
C) NAD+ and NADP+ differ by the presence of an extra phosphate group in NADP+
D) NADP+ is reduced to NADH in glycolysis
E) Don’t know

C) NAD+ and NADP+ differ by the presence of an extra phosphate group in NADP+

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Which coenzyme is used to transfer aldehydes in metabolic reactions?

A) Thiamine pyrophosphate (TPP)
B) NAD+
C) Coenzyme A
D) Biocytin
E) Don’t know

A) Thiamine pyrophosphate (TPP)

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A deficiency in which vitamin would lead to impaired function of NAD+ and NADP+?

A) Vitamin B2
B) Vitamin B3
C) Vitamin B6
D) Vitamin B12
E) Don’t know

B) Vitamin B3

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Which of the following correctly matches the coenzyme with its dietary precursor?

A) FAD - Niacin
B) NAD+ - Riboflavin
C) Coenzyme A - Pantothenic acid
D) Tetrahydrofolate - Vitamin B12
E) Don’t know

C) Coenzyme A - Pantothenic acid

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10. Which of the following statements about NADH and FADH2 is TRUE? A) NADH donates electrons to Complex II of the electron transport chain B) FADH2 transfers electrons directly to oxygen C) NADH transfers electrons via hydride ion transfer, while FADH2 donates electrons as hydrogen atoms D) FADH2 produces more ATP than NADH in oxidative phosphorylation E) Don't know

C) NADH transfers electrons via hydride ion transfer, while FADH2 donates electrons as hydrogen atoms

1. Which of the following correctly describes an exergonic reaction? A) ΔG is positive, and energy is required to drive the reaction B) ΔG is negative, and the reaction is spontaneous C) The reaction is at equilibrium with ΔG = 0 D) The reaction is non-spontaneous and requires ATP hydrolysis E) Don't know

B) ΔG is negative, and the reaction is spontaneous

2. If a reaction has a ΔG of +5.4 kcal/mol, which of the following statements is true? A) The reaction is spontaneous B) The reaction is exergonic C) The reaction requires energy input to proceed D) The reaction will proceed without an enzyme E) Don't know

C) The reaction requires energy input to proceed

3. A reaction reaches equilibrium when: A) The concentration of reactants equals products B) The forward reaction stops completely C) The Gibbs free energy change (ΔG) is zero D) ATP is used to drive the reaction forward E) Don't know

C) The Gibbs free energy change (ΔG) is zero

4. Which of the following conditions makes a reaction more likely to be spontaneous? A) High activation energy B) A decrease in entropy (ΔS < 0) C) A negative free energy change (ΔG < 0) D) A positive free energy change (ΔG > 0) E) Don't know

C) A negative free energy change (ΔG < 0)

5. Which of the following metabolic reactions is typically endergonic? A) ATP hydrolysis B) Glycolysis C) Fatty acid oxidation D) Gluconeogenesis E) Don't know

D) Gluconeogenesis

6. The hydrolysis of ATP is often coupled with endergonic reactions because: A) ATP hydrolysis is endergonic and requires energy input B) ATP hydrolysis releases energy, which drives unfavourable reactions C) ATP acts as an electron donor in redox reactions D) ATP lowers the activation energy of reactions E) Don't know

B) ATP hydrolysis releases energy, which drives unfavourable reactions

7. Which of the following is true about activation energy (Ea)? A) A catalyst increases Ea to slow down the reaction B) High Ea means the reaction will always be endergonic C) Enzymes lower the activation energy to speed up reactions D) Activation energy determines the spontaneity of a reaction E) Don't know

C) Enzymes lower the activation energy to speed up reactions

8. In which of the following scenarios would a reaction likely proceed spontaneously? A) ΔG = 0 B) ΔG is positive and entropy increases C) ΔG is negative and entropy increases D) ΔG is positive, and temperature is high E) Don't know

C) ΔG is negative and entropy increases

1. Which of the following statements about the oxidation of glucose and palmitate is TRUE? A) Both glucose and palmitate oxidation are endergonic B) The oxidation of palmitate releases more energy than glucose C) Glucose oxidation yields more ATP per molecule than palmitate D) Oxygen is not required for the complete oxidation of glucose E) Don't know

B) The oxidation of palmitate releases more energy than glucose Palmitate oxidation (ΔG=−9,770 kJ/mol) releases significantly more energy than glucose oxidation (ΔG=−2,840 kJ/mol), making it a more energy-dense fuel.

2. Why does palmitate yield more energy than glucose upon oxidation? A) Palmitate contains fewer carbon atoms than glucose B) Palmitate has a higher degree of oxidation than glucose C) Palmitate has more reduced carbons, yielding more NADH and FADH2 D) Glucose oxidation bypasses the citric acid cycle E) Don't know

C) Palmitate has more reduced carbons, yielding more NADH and FADH2 Fatty acids like palmitate are highly reduced molecules, meaning they donate more electrons to NADH and FADH2, leading to greater ATP production via oxidative phosphorylation.

3. If a reaction has a ΔG of -2,840 kJ/mol, what does this indicate? A) The reaction is exergonic and releases energy B) The reaction is endergonic and requires energy input C) The reaction is at equilibrium D) The reaction will not proceed without ATP hydrolysis E) Don't know

A) The reaction is exergonic and releases energy A negative ΔG value indicates a spontaneous, energy-releasing (exergonic) reaction, meaning glucose oxidation releases energy for ATP synthesis.

4. Which of the following correctly describes the role of molecular oxygen (O2) in glucose oxidation? A) O2 serves as an electron donor B) O2 is reduced to water at the end of the electron transport chain C) O2 directly oxidises glucose in glycolysis D) O2 acts as a substrate in ATP synthesis E) Don't know

B) O2 is reduced to water at the end of the electron transport chain Molecular oxygen (O2) serves as the final electron acceptor in the electron transport chain, where it is reduced to H2O.

5. How does the Gibbs free energy change (ΔG) relate to ATP production in cellular respiration? A) A highly negative ΔG drives ATP synthesis via substrate-level phosphorylation B) ATP is only synthesised when ΔG is positive C) ATP production is independent of ΔG D) ATP synthesis occurs only when a reaction reaches equilibrium (ΔG=0) E) Don't know

A) A highly negative ΔG drives ATP synthesis via substrate-level phosphorylation Exergonic reactions (negative ΔG) provide the energy needed to drive ATP synthesis in oxidative phosphorylation and substrate-level phosphorylation.

6. Which of the following best explains why glucose is the primary fuel in many organisms despite palmitate yielding more energy? A) Glucose is more oxidized than palmitate, making it a better energy source B) Glucose can be metabolised anaerobically, while palmitate requires oxygen C) Fatty acids yield less ATP per carbon than glucose D) Glucose oxidation produces fewer reactive oxygen species than palmitate oxidation E) Don't know

B) Glucose can be metabolised anaerobically, while palmitate requires oxygen Glucose can be broken down via glycolysis in anaerobic conditions, whereas fatty acids require oxygen for β-oxidation.

7. What happens to excess Gibbs free energy released during glucose oxidation? A) It is stored as glycogen B) It is used to drive ATP synthesis C) It is converted into NADPH for biosynthetic reactions D) It is released as heat without any use E) Don't know

B) It is used to drive ATP synthesis The energy from glucose oxidation is captured in ATP production through oxidative phosphorylation and substrate-level phosphorylation.

What are the 6 key reaction types in metabolism?

1. Oxireductases 2. Transferases 3. Hydrolases 4. Lysases 5. Isomerases 6. Ligases

What are the three rate limiting steps in the TCA cycle?

1. Citrate Synthase 2. Isocitrate Dehydrogenase 3. α-ketoglutarate dehydrogenase

1. Which of the following factors increases the melting temperature of a fatty acid? A) Increasing the number of double bonds B) Decreasing the number of carbons in the chain C) Increasing the number of carbons in the chain D) Presence of cis double bonds E) Don't know

C) Increasing the number of carbons in the chain Longer fatty acid chains have stronger van der Waals interactions, increasing the melting temperature. More double bonds (especially in cis configuration) disrupt packing, lowering Tm.

2. Which of the following fatty acids has the highest melting temperature? A) Stearic acid (18:0) B) Oleic acid (18:1(9)) C) Linoleic acid (18:2(9,12)) D) Arachidonic acid (20:4(5,8,11,14)) E) Don't know

A) Stearic acid (18:0) Saturated fatty acids (like stearic acid) pack tightly, leading to higher melting temperatures. Unsaturation disrupts packing, lowering Tm.

3. Which of the following statements is TRUE regarding the effect of unsaturation on melting temperature? A) A fatty acid with 18 carbons and 2 double bonds has a higher melting temperature than an 18-carbon saturated fatty acid B) The presence of double bonds decreases the melting temperature C) Cis double bonds increase the melting temperature by stabilizing the structure D) Increasing chain length decreases melting temperature E) Don't know

B) The presence of double bonds decreases the melting temperature Double bonds (especially in the cis configuration) introduce kinks that prevent tight packing, reducing van der Waals forces and lowering the melting temperature.

4. Rank the following fatty acids from lowest to highest melting temperature: Linoleic acid (18:2(9,12)) Stearic acid (18:0) Oleic acid (18:1(9)) A) 1 < 2 < 3 B) 2 < 3 < 1 C) 1 < 3 < 2 D) 3 < 1 < 2 E) Don't know

C) 1 < 3 < 2 Stearic acid (18:0) has the highest Tm (no double bonds), followed by Oleic acid (one double bond), and Linoleic acid (two double bonds) has the lowest Tm.

5. Which fatty acid would be more likely to be liquid at room temperature? A) Stearic acid (18:0) B) Arachidonic acid (20:4(5,8,11,14)) C) Lignoceric acid (24:0) D) Palmitic acid (16:0) E) Don't know

B) Arachidonic acid (20:4(5,8,11,14)) Polyunsaturated fatty acids like arachidonic acid have multiple double bonds, significantly lowering their melting temperature and making them more likely to be liquid at room temperature.

6. Which modification would likely convert a solid fat into a liquid at room temperature? A) Increasing the number of carbons in the fatty acid chains B) Decreasing the number of double bonds C) Introducing more cis double bonds D) Hydrogenation of unsaturated fatty acids E) Don't know

C) Introducing more cis double bonds Cis double bonds prevent tight packing of fatty acid chains, lowering the melting temperature and making the fat more likely to be liquid at room temperature.

7. Butter contains a higher proportion of saturated fatty acids compared to olive oil. What does this imply about their melting temperatures? A) Butter has a higher melting temperature than olive oil B) Butter has a lower melting temperature than olive oil C) Butter and olive oil have the same melting temperature D) Butter contains more polyunsaturated fatty acids than olive oil E) Don't know

A) Butter has a higher melting temperature than olive oil Butter is rich in saturated fats, which have higher melting temperatures, making it solid at room temperature, whereas olive oil contains more unsaturated fats, keeping it liquid.

What is the reaction formula for the synthesis of Palmitate?

AcetylCoA + 7 Malonyl-CoA + 14 NADPH → Palmitate + 7 CO2 + 14 NADP+ + 8 CoA

What are the TWO routes to the production of NADPH in fatty acid synthesis?

1. Malic enzyme pathway 2. Pentose Phosphate Pathway

Where does Fatty Acid Synthesis primarily occur in the cell? A) Mitochondria B) Cytoplasm C) Endoplasmic reticulum D) Peroxisome E) Don't know

B) Cytoplasm

Where does β-Oxidation primarily occur in the cell? A) Mitochondria B) Cytoplasm C) Endoplasmic reticulum D) Peroxisome E) Don't know

A) Mitochondria

Which of the following cofactors is primarily used in fatty acid synthesis? A) NADH and FAD B) NADPH C) Coenzyme A D) ATP E) Don't know

B) NADPH Fatty acid synthesis requires NADPH as a reducing agent, whereas beta-oxidation uses NAD+ and FAD for oxidation reactions.

Which of the following cofactors is primarily used in fatty acid synthesis? A) NAD and FAD B) NADPH C) Coenzyme A D) ATP E) Don't know

A) NAD and FAD

What is the energy requirement for Fatty Acid Synthesis?

49 ATP equivalents

What is the energy yield for β-Oxidation?

33 ATP equivalents

What regulates Fatty Acid Synthesis?

Acetyl CoA Carboxylase

What regulates β-Oxidation?

Acetyl CoA

What molecules are generated during the β-Oxidation of fatty acids?

7 NAD+ 7 FAD 7 NADH + H+ 7 FADH2 8 Acetyl-CoA

What is the rate limiting step in glycolysis?

Phosphofructokinase

Which glycosidic bonds does amylase cleave?

α 1-4

What is the most common monomer of carbohydrate?

Glucose

What type of reactions is Biotin involved in?

Carboxylations

TRUE OR FALSE: Glycerol Kinase is not present in adipose tissue

True

Ribose is a pentose sugar found in: A) NAD B) FAD C) RNA D) ATP E) All of the above

E) All of the above

Which glucose transporter mediates insulin dependent uptake of glucose?

GLUT4

How many protons and electrons does the synthesis of 2H20 through oxidative phosphorylation require?

10 H+ and 4 electrons

NADPH is: A) A strong reductant in metabolism B) Specific for certain enzymes C) Utilised in nitric oxide synthesis D) In excess in some tissues E) All of the above

E) All of the above

As the end product of glycolysis, pyruvate and NADH is formed, during aerobic conditions, the NAD+ is regenerated by: A) Glyceraldehyde-3-phosphate dehydrogenase B) Glutamate dehydrogenase C) Lactate dehydrogenase D) Oxygen E) Hydrogen

D) Oxygen Under AEROBIC conditions, it is regenerated by oxygen Under ANAEROBIC conditions, its is regenerated by lactate dehydrogenase

NAD and NADP are electron carriers dervived from: A) Riboflavin B) Vitamin B3 C) Vitamin B12 D) Vitamin B1 E) Vitamin D

B) Vitamin B3

All of the following is true of the Warburg effect EXCEPT: A) Increased utilisation of glucose B) Increased production of lactate C) Production of 2 ATP molecules per cycle D) Reduction of NAD E) Synthesis of Acetyl-CoA

E) Synthesis of Acetyl-CoA In the Warburg effect, most pyruvate is converted to lactate, NOT Acetyl-CoA. Acetyl-CoA synthesis occurs when pyruvate enters the mitochondria and is converted by pyruvate dehydrogenase (PDH), which is often downregulated in cancer cells.