Krebs Cycle: Interactive Learning Quizzes for Biochemistry Students

Question 1

In the Krebs cycle, which enzyme catalyzes the decarboxylation reaction where carbon dioxide is released?

Accepted Answer

α-Ketoglutarate dehydrogenase

Answer

Citrate synthase

Answer

Isocitrate dehydrogenase

Answer

Succinyl-CoA synthetase

Question 2

What is the primary function of the Krebs cycle in cellular metabolism?

Accepted Answer

To produce NADH and FADH2 for electron transport

Answer

To generate ATP through oxidative phosphorylation

Answer

To synthesize amino acids and nucleotides

Answer

To break down glucose through glycolysis

Question 3

Which molecule undergoes a series of dehydrogenation reactions to form succinyl-CoA?

Accepted Answer

α-Ketoglutarate

Answer

Citrate

Answer

Isocitrate

Answer

Succinate

Question 4

Which enzyme is involved in regulating the entry point into the Krebs cycle?

Accepted Answer

Citrate synthase

Answer

Isocitrate dehydrogenase

Answer

α-Ketoglutarate dehydrogenase

Answer

Pyruvate dehydrogenase

Question 5

What is the final product of the Krebs cycle?

Accepted Answer

Oxaloacetate

Answer

Malate

Answer

Fumarate

Answer

Citrate

Question 6

Which of the following compounds is NOT involved in the Krebs cycle as a substrate?

Accepted Answer

Glucose

Answer

Acetyl-CoA

Answer

Isocitrate

Answer

Malate

Question 7

Which condition is associated with a deficiency in Krebs cycle enzymes?

Accepted Answer

Mitochondrial disorders

Answer

Vitamin B12 deficiency

Answer

Diabetes mellitus

Answer

Hyperthyroidism

Question 8

Which enzyme is responsible for catalyzing the decarboxylation of α-ketoglutarate to succinyl-CoA?

Accepted Answer

α-Ketoglutarate dehydrogenase

Answer

Citrate synthase

Answer

Isocitrate dehydrogenase

Answer

Succinyl-CoA synthetase

Question 9

What role do NADH and FADH2 play in the Krebs cycle?

Accepted Answer

They are electron carriers

Answer

They are energy sources

Answer

They are coenzymes for enzymes

Answer

They regulate the cycle

Question 10

Which of the following substances acts as an allosteric activator of citrate synthase?

Accepted Answer

Acetyl-CoA

Answer

Succinyl-CoA

Answer

ATP

Answer

NADH

Question 11

Which intermediate of the Krebs cycle can be transported out of the mitochondria?

Accepted Answer

Oxaloacetate

Answer

Acetyl-CoA

Answer

α-Ketoglutarate

Answer

Succinyl-CoA

Question 12

Which metabolic pathway primarily generates the NADH and FADH2 that drive the electron transport chain?

Accepted Answer

Citric acid cycle

Answer

Glycolysis

Answer

Pentose phosphate pathway

Answer

Fatty acid oxidation

Question 13

Which substance acts as the initial substrate for the Krebs cycle?

Accepted Answer

Acetyl-CoA

Answer

Oxaloacetate

Answer

Pyruvate

Answer

Citrate

Question 14

What is the primary role of oxaloacetate in the Krebs cycle?

Accepted Answer

Is regenerated to initiate subsequent cycles

Answer

Serves as the initial substrate

Answer

Participates in the production of GTP

Answer

Acts as an electron carrier

Question 15

Analyze the potential consequences of dysregulation in the Krebs cycle, considering its role in the development of diseases and metabolic disorders.

Accepted Answer

Dysregulation in the Krebs cycle can contribute to the development of cancer.

Accepted Answer

Mitochondrial disorders can arise from dysregulation in the Krebs cycle.

Accepted Answer

Diabetes can be influenced by dysregulation in the Krebs cycle.

Answer

Dysregulation in the Krebs cycle is not directly linked to the development of cardiovascular diseases.

Question 16

What is NADH's primary role in the citric acid cycle?

Accepted Answer

Electron carrier

Answer

Activator

Answer

Coenzyme

Answer

Substrate

Question 17

Which enzyme catalyzes the dehydration reaction that converts citrate to cis-aconitate?

Accepted Answer

Aconitase

Answer

α-ketoglutarate dehydrogenase

Answer

Isocitrate dehydrogenase

Question 18

Which factor primarily regulates the citric acid cycle?

Accepted Answer

NADH/NAD+ ratio

Answer

Temperature

Answer

pH

Answer

Ca2+ concentration

Question 19

What is the central significance of the citric acid cycle in cellular metabolism?

Accepted Answer

Generation of reducing equivalents (NADH, FADH2) and ATP

Answer

Storage of genetic information

Answer

Breakdown of carbohydrates

Answer

Synthesis of amino acids

Question 20

Which of the following is NOT a product of the citric acid cycle?

Accepted Answer

Glycerol

Answer

NADH

Answer

FADH2

Answer

ATP

Question 21

What is the overall chemical equation for the citric acid cycle?

Accepted Answer

Acetyl-CoA + 3 NAD+ + FAD + ADP + Pi → 2 CO2 + 3 NADH + FADH2 + ATP + CoA

Answer

Glucose + 6 O2 → 6 CO2 + 6 H2O + energy

Answer

Pyruvate + NADH + H+ → Lactate + NAD+

Question 22

Where does the citric acid cycle take place within eukaryotic cells?

Accepted Answer

Mitochondrial matrix

Answer

Nucleus

Answer

Cytoplasm

Answer

Golgi apparatus

Question 23

How does the citric acid cycle contribute to lipid metabolism?

Accepted Answer

Provides precursors for fatty acid synthesis and acetyl-CoA

Answer

Generates reducing equivalents for lipid catabolism

Answer

Regulates lipid signaling pathways