The Krebs Cycle

What is the Krebs Cycle?

A series of enzymatic reactions that occur in the mitochondria, producing energy through the oxidation of acetyl-CoA.

Where does the Krebs Cycle take place?

In the mitochondria of eukaryotic cells.

What molecule initiates the Krebs Cycle?

Acetyl-CoA.

What are the main products of one turn of the Krebs Cycle?

3 NADH, 1 FADH₂, 1 ATP (or GTP), and 2 CO₂.

What is the role of NAD+ in the Krebs Cycle?

NAD+ acts as an electron carrier, being reduced to NADH.

What is the role of FAD in the Krebs Cycle?

FAD acts as an electron carrier, being reduced to FADH₂.

How many times does the Krebs Cycle turn per glucose molecule?

Twice, since one glucose molecule produces two acetyl-CoA.

What enzyme converts pyruvate to acetyl-CoA?

Pyruvate dehydrogenase.

What is the importance of oxaloacetate in the Krebs Cycle?

Oxaloacetate combines with acetyl-CoA to start the cycle and is regenerated at the end.

What happens to the carbon atoms during the Krebs Cycle?

They are released as CO₂ during the oxidation of acetyl-CoA.

What role does water play in the Krebs Cycle?

Water is involved in the hydration and dehydration reactions of the cycle.

What is the effect of oxygen on the Krebs Cycle?

Oxygen is not directly used in the Krebs Cycle, but it is critical for mitochondrial function.

Which substrate-level phosphorylation occurs in the Krebs Cycle?

The conversion of succinyl-CoA to succinate, producing ATP or GTP.

What is citrate?

The first product formed in the Krebs Cycle when acetyl-CoA combines with oxaloacetate.

What is the significance of GTP in the Krebs Cycle?

GTP produced can be converted to ATP for energy use.

What is fumarate?

A four-carbon intermediate produced during the Krebs Cycle.

How is malate produced in the Krebs Cycle?

Fumarate is hydrated to form malate.

What is the final product of the Krebs Cycle?

Oxaloacetate is regenerated to maintain the cycle.

What role does succinate dehydrogenase play?

Converts succinate to fumarate while reducing FAD to FADH₂.

What is the relationship between the Krebs Cycle and the electron transport chain?

NADH and FADH₂ generated in the Krebs Cycle donate electrons to the electron transport chain.

In what cellular process is the Krebs Cycle vital?

Aerobic respiration.

How many NADH molecules are produced per glucose molecule during the Krebs Cycle?

6 NADH molecules.

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

2 FADH₂ molecules.

What are the two main phases of the Krebs Cycle?

The preparatory phase and the cycle of reactions.

What is the result of inhibiting the Krebs Cycle?

Decreased ATP production and impaired cellular energy metabolism.

What intermediates are often used in amino acid synthesis from the Krebs Cycle?

Alpha-ketoglutarate and oxaloacetate.

How is the Krebs Cycle regulated?

Through allosteric enzymes and substrate availability.

What is the connection between the Krebs Cycle and metabolic diseases?

Disruptions in the cycle can lead to energy deficiencies and metabolic disorders.

What is the role of acetyl-CoA beyond the Krebs Cycle?

Acetyl-CoA is also utilized in lipid synthesis and ketogenesis.

What is anaplerosis in relation to the Krebs Cycle?

The process of replenishing cycle intermediates that are consumed.

Why is the Krebs Cycle considered a central metabolic pathway?

It plays a role in multiple metabolic processes including energy production, biosynthesis, and waste removal.