The Krebs Cycle Flashcards
Where in the cell does the Krebs cycle take place?
The Krebs cycle takes place in the mitochondrial matrix.
What molecule is introduced to the Krebs cycle from the link reaction?
Acetyl-CoA.
Is oxygen needed as a reactant in the Krebs cycle?
No
How many carbon atoms are in oxaloacetate?
4
How many carbon atoms are in citrate?
6
Where did the extra carbon atoms come from to convert oxaloacetate into citrate?
Two carbons are in the acetyl group that enters the Krebs cycle from the link reaction.
How many carbon atoms are in α-ketoglutarate?
5
Where did the missing carbon atom go during the conversion of citrate to α-ketoglutarate?
A molecule of carbon dioxide (containing one carbon atom) was produced during the conversion.
How many carbon atoms are in succinate?
4
Where did the missing carbon atom go during the conversion of α-ketoglutarate to succinate?
A molecule of carbon dioxide (containing one carbon atom) was produced during the conversion.
Throughout the Krebs cycle, energy is transferred to other high potential energy molecules. List those molecules and indicate the number produced with one “turn” of the cycle.
Each “turn” of the Krebs cycle makes one ATP molecule, three NADH molecules, and one FADH2 molecule.
Which molecule in the Krebs cycle has the highest potential energy—citrate, α-ketoglutarate, succinate or oxaloacetate?
Citrate has the highest potential energy because as it moves through the Krebs cycle, energy is released in the form of ATP, NADH, and FADH2.
Which molecule in the Krebs cycle has the lowest potential energy—citrate, α-ketoglutarate, succinate or oxaloacetate?
Oxaloacetate has the lowest potential energy because it is the result of several reactions where energy has been released in the form of ATP, NADH, and FADH2.
Considering your answers to the previous three questions, what can you conclude about the potential energy of the acetyl group that is carried from the link reaction to the Krebs cycle by coenzyme A? Does this group of atoms have a high potential energy or a low potential energy?
The acetyl group must have a high potential energy because it converts a low potential energy molecule (oxaloacetate) to a high potential energy molecule (citrate).
How many “turns” of the Krebs cycle occur for every glucose molecule (C6H12O6) that undergoes cellular respiration?
The Krebs cycle must complete two “turns” for each glucose molecule. Each glucose molecule makes two pyruvate molecules, which react to form two acetyl-CoA molecules.
How many of each of the molecules below are produced in the Krebs cycle of every glucose molecule that undergoes cellular respiration?
CO2-2
ATP-2
NADH-6
FADH2-2
Was oxygen used as a reactant in any of the processes explored in this activity—glycolysis, the link reaction or the Krebs cycle?
No
