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Glycolysis: Unraveling the Initial Steps of Glucose Breakdown

Description: Glycolysis: Unraveling the Initial Steps of Glucose Breakdown
Number of Questions: 15
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Tags: biochemistry glycolysis glucose metabolism
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Glycolysis is the first stage of cellular respiration in which glucose is broken down to produce energy. What is the net gain of ATP molecules during glycolysis?

  1. 2 ATP

  2. 4 ATP

  3. 6 ATP

  4. 8 ATP


Correct Option: A
Explanation:

During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate, yielding a net gain of 2 ATP molecules.

Which enzyme catalyzes the first step of glycolysis, where glucose is phosphorylated to form glucose-6-phosphate?

  1. Hexokinase

  2. Phosphofructokinase

  3. Glyceraldehyde-3-phosphate dehydrogenase

  4. Pyruvate kinase


Correct Option: A
Explanation:

Hexokinase is the enzyme responsible for the initial phosphorylation of glucose, converting it into glucose-6-phosphate.

Which intermediate molecule in glycolysis is isomerized to form fructose-6-phosphate?

  1. Glucose-6-phosphate

  2. Glucose-1-phosphate

  3. Fructose-1,6-bisphosphate

  4. 3-Phosphoglycerate


Correct Option: A
Explanation:

Glucose-6-phosphate is isomerized to fructose-6-phosphate by the enzyme phosphoglucomutase.

Which step in glycolysis involves the cleavage of fructose-1,6-bisphosphate into two molecules of glyceraldehyde-3-phosphate?

  1. Phosphorylation

  2. Isomerization

  3. Cleavage

  4. Oxidation


Correct Option: C
Explanation:

The cleavage of fructose-1,6-bisphosphate into two molecules of glyceraldehyde-3-phosphate is catalyzed by the enzyme aldolase.

What is the role of glyceraldehyde-3-phosphate dehydrogenase in glycolysis?

  1. Oxidizes glyceraldehyde-3-phosphate to form 1,3-bisphosphoglycerate

  2. Converts glyceraldehyde-3-phosphate to dihydroxyacetone phosphate

  3. Phosphorylates glyceraldehyde-3-phosphate to form 1,3-bisphosphoglycerate

  4. Reduces glyceraldehyde-3-phosphate to form glycerol-3-phosphate


Correct Option: A
Explanation:

Glyceraldehyde-3-phosphate dehydrogenase catalyzes the oxidation of glyceraldehyde-3-phosphate to form 1,3-bisphosphoglycerate.

Which enzyme catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate?

  1. Phosphoglycerate kinase

  2. Phosphoglyceromutase

  3. Enolase

  4. Pyruvate kinase


Correct Option: A
Explanation:

Phosphoglycerate kinase catalyzes the transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP, forming 3-phosphoglycerate and ATP.

What is the role of enolase in glycolysis?

  1. Converts 3-phosphoglycerate to 2-phosphoglycerate

  2. Converts 2-phosphoglycerate to phosphoenolpyruvate

  3. Converts phosphoenolpyruvate to pyruvate

  4. Converts dihydroxyacetone phosphate to glyceraldehyde-3-phosphate


Correct Option: B
Explanation:

Enolase catalyzes the dehydration of 2-phosphoglycerate to form phosphoenolpyruvate.

Which enzyme catalyzes the final step of glycolysis, where phosphoenolpyruvate is converted to pyruvate?

  1. Phosphoglycerate kinase

  2. Phosphoglyceromutase

  3. Enolase

  4. Pyruvate kinase


Correct Option: D
Explanation:

Pyruvate kinase catalyzes the transfer of a phosphate group from phosphoenolpyruvate to ADP, forming pyruvate and ATP.

How many molecules of NADH are produced during glycolysis?

  1. 2

  2. 4

  3. 6

  4. 8


Correct Option: A
Explanation:

Two molecules of NADH are produced during glycolysis, one from the oxidation of glyceraldehyde-3-phosphate and one from the oxidation of phosphoenolpyruvate.

Which molecule is the final product of glycolysis?

  1. Glucose-6-phosphate

  2. Fructose-1,6-bisphosphate

  3. Glyceraldehyde-3-phosphate

  4. Pyruvate


Correct Option: D
Explanation:

Pyruvate is the final product of glycolysis, which is then converted to acetyl-CoA and enters the citric acid cycle.

Glycolysis occurs in which cellular compartment?

  1. Cytoplasm

  2. Mitochondria

  3. Nucleus

  4. Endoplasmic reticulum


Correct Option: A
Explanation:

Glycolysis takes place in the cytoplasm of cells, where glucose is broken down into pyruvate.

Which hormone stimulates glycolysis in response to increased energy demands?

  1. Insulin

  2. Glucagon

  3. Epinephrine

  4. Thyroxine


Correct Option: C
Explanation:

Epinephrine stimulates glycolysis by activating enzymes involved in the breakdown of glucose.

What is the overall energy yield of glycolysis in terms of ATP molecules?

  1. 2 ATP

  2. 4 ATP

  3. 6 ATP

  4. 8 ATP


Correct Option: A
Explanation:

Glycolysis yields a net gain of 2 ATP molecules, along with 2 molecules of NADH and 2 molecules of pyruvate.

Which metabolic pathway continues after glycolysis to further break down pyruvate and generate energy?

  1. Citric acid cycle

  2. Electron transport chain

  3. Oxidative phosphorylation

  4. Gluconeogenesis


Correct Option: A
Explanation:

The citric acid cycle, also known as the Krebs cycle, is the next step in cellular respiration after glycolysis, where pyruvate is further broken down to generate energy.

What is the significance of glycolysis in cellular metabolism?

  1. Provides energy in the form of ATP

  2. Generates NADH and FADH2 for oxidative phosphorylation

  3. Produces pyruvate for entry into the citric acid cycle

  4. All of the above


Correct Option: D
Explanation:

Glycolysis plays a crucial role in cellular metabolism by providing energy in the form of ATP, generating NADH and FADH2 for oxidative phosphorylation, and producing pyruvate for entry into the citric acid cycle.

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