IB Biology HL C1.2.12 Hl Krebs Cycle Questions

Trace acetyl-CoA combining with oxaloacetate to form citrate, then follow cycle regeneration and production of CO₂, ATP, reduced NAD and FAD in IB Biology HL C1.2.12.

Exam points

Explain that acetyl-CoA combines with oxaloacetate to form citrate at the start of the Krebs cycle.
Explain how the cycle regenerates oxaloacetate while releasing CO₂ and producing ATP, reduced NAD and reduced FAD.

[Maximum number: 8]

Explain the processes involved in the Krebs cycle.

Krebs cycle only occurs in aerobic conditions;
the Krebs cycle occurs in the mitochondria;
acetyl CoA from the link reaction releases an acetyl group;
$\mathrm{NADH}+\mathrm{H}^{+}$ and $\mathrm{CO}_{2}$ are formed (with each decarboxylation);
decarboxylation/removal of $\mathrm{CO}_{2}$ involves oxidation/oxidative decarboxylation;
and the release of energy;
acetyl group is joined to a 4-carbon molecule/ $\mathrm{C}_{4} /$ oxaloacetate to form a 6-carbon molecule/citrate;
(decarboxylation changes citrate) to 5-carbon molecule/ $\mathrm{C}_{5}$ ;
(decarboxylation changes glutamate) to a 4-carbon molecule/ $\mathrm{C}_{4}$ ;
then converted into the original 4-carbon molecule/ $\mathrm{C}_{4} /$ oxaloacetate and the cycle repeats;
one (molecule) of ATP is made during this step;
reduced H-carriers/ NADH and FADH2 and carbon dioxide are end-products of Krebs cycle;

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IB Biology HL C1.2.12 Hl Krebs Cycle Questions question 1