IB Biology HL C1.2.12 Hl Krebs Cycle Questions

Practise IB Biology HL 1.2.12 by applying krebs cycle concepts to exam questions.

Exam points

Locate the Krebs cycle in the mitochondrial matrix and identify acetyl-CoA as its entering substrate.
Identify decarboxylation, oxidation and reduction reactions and the formation of reduced NAD or FAD in the cycle.
Interpret carbon-count and respiration-stage evidence to explain cycle intermediates and carbon-dioxide release.

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Study C1.2.12 (HL)—Krebs cycle conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

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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