Krebs cycle

Krebs cycle

  • takes place in the mitochondrial matrix

  • processes acetyl CoA to prepare substrates for the final stage of aerobic respiration

For each molecule of acetyl CoA:

  • 2x molecules of CO2 produced as by-product

  • electron carriers including 3x molecules of reduced NAD and 1x reduced FAD produced

  • 1x molecule of ATP produced

Krebs cycle as a series of enzymatic reactions

  1. acetyl CoA merges with a 4C molecule, oxoacetate, to create a 6C molecule, citrate

  2. citrate is decarboxylated, releasing two molecules of CO2 in two stages

  1. citrate is also dehydrogenated (oxidised), releasing hydrogens that reduce three molecules of NAD and one molecules of FAD

  2. for each acetyl CoA that enters the cycle, one ATP is synthesised directly via substrate level phosphorylation

  3. oxoacetate is regenerated for the next turn of the cycle

Krebs cycle

The role of coenzymes

  • initially act as oxidising agents

  • reduced coenzymes later donate these gained electrons to the electron transport chain

  • facilitates the transfer of electrons that is crucial for the synthesis for the synthesis of ATP

Importance of the Krebs cycle

  • oxidises and breaks down large nutrients into smaller ones

    • eg CO2 which can be removed as waste

  • generates reduced NAD and reduced FAD

    • carry electrons and protons into oxidative phosphorylation

  • continually regenerates the 4C molecule to combine with acetyl CoA

  • provides a variety of intermediate compounds required for the biosynthesis of essential cellular components such as fatty acids, amino acids, and chlorophyll