Krebs Cycle and Cellular Respiration

The Krebs cycle is the second step in cellular respiration, requiring oxygen and occurring in the mitochondria. It begins with pyruvate from glycolysis, forming acetyl CoA, which enters the cycle. The cycle produces citric acid, releasing CO2, ATP, NADH, and FADH2. These molecules store electrons used in the electron transport chain, the final stage of cellular respiration. The cycle's total yield is 2 ATP, 6 NADH, and 2 FADH2 per glucose molecule, highlighting its importance in energy production.

What is the primary requirement for the Krebs Cycle to proceed?

• Water

• Glucose

• Oxygen

• Carbon dioxide

Where does the Krebs Cycle occur within the cell?

• Nucleus

• Cytoplasm

• Cell membrane

• Inner matrix of the mitochondria

What molecule is formed when pyruvate combines with co-enzyme A?

• FADH2

• Acetyl CoA

• NADH

• Citric acid

During the Krebs Cycle, what is released from citric acid?

• Oxygen

• Water

• Carbon dioxide

• Glucose

How many NADH molecules are produced from one turn of the Krebs Cycle?

• One

• Two

• Three

• Four

What is the role of FADH2 in cellular respiration?

• It breaks down glucose into pyruvate.

• It transports oxygen to the mitochondria.

• It acts as a catalyst in glycolysis.

• It stores high-energy electrons for the electron transport chain.

Why must the products of the Krebs Cycle be doubled?

• To account for energy loss.

• Because two pyruvate molecules are produced from glycolysis.

• To balance the chemical equation.

• Because two glucose molecules are used.

What is the total ATP yield from the Krebs Cycle per glucose molecule?

• 4 ATP

• 8 ATP

• 2 ATP

• 6 ATP

How many FADH2 molecules are produced from the Krebs Cycle per glucose molecule?

• One

• Two

• Three

• Four

What is the next stage of cellular respiration after the Krebs Cycle?

• Fermentation

• Electron transport chain

• Photosynthesis

• Glycolysis