Krebs Cycle

Question 1

what is the Krebs cycle?

Answer 1

• a series of enzyme controlled reactions, where the acetyl group from aceytl COo-A is accepted and converted into a series of other substances

Question 2

Where does the kreb cycle take place?

Answer 2

• in the mitochondrial matrix

Question 3

What happens during the cycle?

Answer 3

• very small amount of ATP is made directly (substrate level phosphorylation)
• Decarboxylation occurs (loss of CO2
• Dehydrogenation occurs (loss of hydrogen atoms)

Question 4

what co-enzymes are involved?

Answer 4

• NAD and FAD

Question 5

How does FAD become reduce?

Answer 5

• It is reduced when it picks up hydrogen atoms

Question 6

What are the stages of kreb cycle?

Answer 6

• the aceytl group released from aceytl coA combines with a four-carbon compound, oxaloacetate to form a six carbon compound
• citrate is decarboxylated and dehydrogenated, producing a five carbon compound, one molecule of carbon dioxide and one molecule of reduced NAD
• this five carbon compound is further decarboxylated and dehydrogenated, producing a four- carbon compound, one molecule of carbon dioxide and one molecule of reduced NAD
• This four carbon compound combine temporarily with, and is then released from, coenzyme A. At this stage, substrate level phosphorlyation takes place, producing one molecule of ATP.
• the four carbon compound is dehydrogenated, producing a different four-carbon compound and a molecule of reduced NAD.
• Rearrangement of the atoms in the four-carbon molecule, catalysed by an isomerase enzyme followed by further dehyrogenation, regenerate a molecule of oxaloacetate so the cycle can continue.

Question 7

How much ATP has been made at the end of the kreb cycle?

Answer 7

• very little ATP

Question 8

What has been released?

Answer 8

• Lots of hydrogen atoms have been released along the way

Question 9

Where have the hydrogen atoms been passed on to?

Answer 9

• they have past to mostly NAD, some to FAD, reducing them

Question 10

What do the co-enzymes then do?

Answer 10

• they carry the hydrogen atoms to the cristae of the mitochondria and release them

Question 11

What part of the respiration will the co-enzymes be involved in?

Answer 11

• They will be involved in the last part of the reaction (Oxidative respiration) where a lot more ATP will be made.