Krebs Cycle

This set of flashcards covers key vocabulary and concepts related to aerobic metabolism and the Krebs cycle, important for understanding energy production in cells.

Krebs cycle

An aerobic metabolic pathway in the mitochondria that produces energy by oxidizing acetyl CoA.

Occurs in the mitochondrial matrix

Pyruvate

A key intermediate in the metabolism of glucose during glycolysis, which can be converted to lactate or acetyl CoA.

Pyruvate Dehydrogenase

Converts pyruvate to acetyl-CoA

• Occurs in matrix

• Electrons from G3P are transferred into mitochondria

• Produced NADH helps to recycle NAD in the cytosol

Krebs cycle key ingridients

Acetyl-CoA and Oxaloacetate

Acetyl CoA

The starting material for the Krebs cycle, generated from pyruvate.

Oxaloacetate

A four-carbon molecule that combines with acetyl CoA to initiate the Krebs cycle.

Citrate

The six-carbon molecule formed from the combination of acetyl CoA and oxaloacetate.

Citrate synthase

The enzyme that catalyzes the formation of citrate from acetyl CoA and oxaloacetate.

FADH2

A reduced coenzyme that carries electrons, produced in the Krebs cycle.

Electron transport chain

A series of complexes that transfer electrons from NADH and FADH2 to produce ATP.

Krebs Cycle (initial steps)

• Citrate undergoes reactions to remove carbons and regenerate NADH

• First carbon is removed as CO2, transitioning from a six-carbon to a five-carbon molecule.

Krebs Cycle (second step)

• Second CO2 is released; five-carbon reduced to a four-carbon molecule.

• No ATP produced yet, focus remains on producing NADH for electron transport.

Krebs Cycle (Substrate level phosphorylation)

• One occurrence in the Krebs cycle:

  • ATP produced directly without electron transfer.

  • Precise moment of phosphorylation occurs while retaining the four-carbon structure.

Krebs Cycle (final steps)

• Additional hydrogen and electrons are stripped off, involved in the creation of:

  • FADH2: New electron carrier produced in one step.

  • Another reaction regenerates NADH with the formation of oxaloacetate.

• Krebs cycle is cyclic:

  • Returns to oxaloacetate to join with new acetyl CoA.

Products produced per cycle

• NADH: 3 per cycle

• FADH2: 1 per cycle

• ATP: 1 per cycle

• Glucose: 1 per cycle

• Cycles in total: 2 (due to 2 Acetyl-CoA produced)