Link reaction and Krebs cycleEdexcel International A Level Biology: Mind map

Exam questions on Link reaction and Krebs cycle

1. In a muscle cell, glycolysis in the cytoplasm produces pyruvate. This pyruvate is transported into the mitochondria, where it is converted to a two-carbon compound that can enter the Krebs cycle.
   Explain why the conversion of pyruvate to the two-carbon compound is described as oxidative decarboxylation.2 marks
2. A researcher studies the Krebs cycle in isolated liver mitochondria supplied with the product of the link reaction. For one molecule of glucose, the Krebs cycle turns twice, once for each pyruvate formed.
   The Krebs cycle does not use oxygen directly, but it stops when oxygen is absent. Explain why.2 marks
3. A suspension of isolated mitochondria is supplied with 0.0020 mol of pyruvate and plenty of oxygen. Assume that all of the pyruvate is completely oxidised by the link reaction and the Krebs cycle, and that one mole of any gas occupies 24 000 cm³ at room temperature and pressure.
   Calculate the volume of carbon dioxide released from the 0.0020 mol of pyruvate.3 marks