IB Diploma Biology: Metabolic Pathways Quiz

What is the primary function of glycolysis?

• To generate oxygen for the cell

• To break down glucose and produce ATP

• To convert glucose into glycogen

• To produce carbon dioxide for cellular respiration

Answer explanation

The primary function of glycolysis is to break down glucose and produce ATP, which is essential for cellular energy. The other options do not accurately describe the main role of glycolysis.

How many carbon atoms does one molecule of glucose contain?

• 3

• 4

• 5

• 6

Answer explanation

One molecule of glucose contains 6 carbon atoms, which is represented by the chemical formula C6H12O6. Therefore, the correct answer is 6.

During glycolysis, how many molecules of pyruvate are produced per glucose molecule?

• 1

• 2

• 3

• 4

Answer explanation

During glycolysis, one glucose molecule is broken down into two molecules of pyruvate. Therefore, the correct answer is 2.

What type of phosphorylation occurs during glycolysis?

• Oxidative phosphorylation

• Substrate-level phosphorylation

• Photophosphorylation

• Chemiosmotic phosphorylation

Answer explanation

During glycolysis, substrate-level phosphorylation occurs when a phosphate group is directly transferred to ADP from a phosphorylated intermediate, resulting in the production of ATP without the involvement of an electron transport chain.

Which molecule donates electrons to NAD⁺ during glycolysis?

• ATP

• Pyruvate

• Glyceraldehyde-3-phosphate

• Oxaloacetate

Answer explanation

Glyceraldehyde-3-phosphate donates electrons to NAD⁺ during glycolysis, converting it to NADH. This step is crucial for energy production in the pathway.

Which of the following best describes glycolysis?

• It occurs only in aerobic conditions

• It produces a high yield of ATP compared to the Krebs cycle

• It is an anaerobic process that does not require oxygen

• It takes place inside the mitochondria

Answer explanation

Glycolysis is an anaerobic process that occurs in the cytoplasm and does not require oxygen. It breaks down glucose to produce ATP, making it distinct from aerobic processes like the Krebs cycle.

What is the first stage of glycolysis called?

• Hydrolysis phase

• Energy investment phase

• Decarboxylation phase

• ATP synthesis phase

Answer explanation

The first stage of glycolysis is called the energy investment phase because it requires the input of ATP to phosphorylate glucose, preparing it for subsequent breakdown and energy extraction.

If a cell lacks oxygen, what happens to the pyruvate produced in glycolysis?

• It enters the Krebs cycle

• It is converted into lactate or ethanol

• It accumulates and stops glycolysis

• It is used to form more glucose

Answer explanation

When a cell lacks oxygen, pyruvate cannot enter the Krebs cycle. Instead, it is converted into lactate in animals or ethanol in yeast, allowing glycolysis to continue by regenerating NAD+.

How many molecules of NADH are produced per molecule of glucose in glycolysis?

• 1

• 2

• 3

• 4

Answer explanation

In glycolysis, each molecule of glucose is converted into two molecules of pyruvate, producing 2 molecules of NADH in the process. Therefore, the correct answer is 2.

In the absence of oxygen, glycolysis is followed by:

• The Krebs cycle

• The electron transport chain

• Fermentation

• The link reaction

Answer explanation

In the absence of oxygen, glycolysis is followed by fermentation, which allows for the regeneration of NAD+ and enables glycolysis to continue producing ATP without oxygen.