Acetyl CoA And Citric Cycle Flashcards
Where is pyruvate transferred to in aerobic respiration and why
Mitochondria to be converted into acetyl coA
Which enzyme removed/ oxidises pyruvate of H+
Pyruvate dehydrogenase
What is pyruvate dehydrogenase part of
A multi enzyme complex with other enzymes involved
Apart from dehydrogenase removing oxidating pyruvate what happens
Decarboxylation
Which vitamins are needed to convert pyruvate to acetyl coa
B1- thiamine pyrophosphate
Riboflavin- FAD
Niacin- NAD
Explain the process of reducing pyruvate using the 3 cofactor vitamins aswell as pyruvate dehydrogenase
Thiamine pyrophosphate removes H from pyruvate to produce thiamine
This then passes it to FAD to be reduced into FADH2
This then allows reduction by passing of H to nad to produce NADH2
Apart from the pyruvate conversion to acetyl coa , what other fates does it have
1- pyruvate can be turned into fatty acids to then be stored as triglycerides storage for energy
2- can be turned into amino acids for anabolic growth
3- anaerobic respiration into lactate
How is pyruvate converted to amino acids
Addition of amine groups
How is pyruvate converted into lactate to regenerate NAD in anaerobic respiration
NADH is oxidised and 2H is used to reduce pyruvate producing lactate
What happens when lactate is produced , how can it be converted back if 02 is present
Lactate dehydrogenase removed H and converts it back into pyruvate
What occurs in yeast when pyruvate is reduced by NADH into NAD?
It produces ethanol
What is the net gain from pyruvate dehydrogenase process (2 cycles)
2 x acetyl coa
2 co2
2 NADH
What is the main importance of the citric acid cycle/ Krebs cycle
Forms reducing power (NADH and FADH)
What type of reaction occurs that joins oxaloacetate (4C) with acetyl coA (2C)
Condensation reaction
Which enzyme catalyses the condensation of oxaloacetate with acetyl coA into citrate
Citrate synthase (6C)
What happens to citrate 6C when produced by condensation citrate synthase
Rearrangement occurs
Citrate into isocitrate (isomer of citrate)
How is citrate rearranged into isocitrate (which enzyme)
Aconitase enzyme
What happens to isocitrate to be converted into a- ketoglutarate
Gets oxidised by isocitrate dehydrogenase which converts NAD into NADH
Also gets decarboxylated
What is it called when eg isocitrate gets both dehydroxylated by isocitrate dehydrogenase and decarboxylated removing co2
Oxidative decarboxylation (occurs to pyruvate aswell)
What happens to a-ketoglutarate (5C) when produced from isocitrate dehydrogenase
Oxidative decarboxylation again (forming NADH and co2)
This forms succinyl coA (thioester bond)
Which enzyme oxidative decarboxylates a keto glutarate
A ketoglutarate dehydrogenase
How is succinyl coA formed (4C)
CoA is added to form thioester with a ketoglutarate produced by isocitrate dehydrogenase
CoA -S- forms a thioester with a ketoglutarate
What happens when the thioester bond on succinyl coA is hydrolysed
Used to generate GTP from GDP + pi
Energy production
What happens when the succinyl coA thioester is hydrolysed
Succinyl coA synthetase regenerates a succinate molecule (4C)
How is succinate converted into fumarate (4C)
Succinate dehydrogenase reduces FAD into FADH oxidising succinate into fumarate
What happens when fumarate is produced
Converted into malate by fumarase enzyme
Adds H2O molecule (hydration)
Where in the Krebs cycle does hydration h20 happen
Fumarate into malate
How is malate converted into oxaloacetate
Malate dehydrogenase reduces NAD into NADH
What is the net gain of Molecules in 2 Krebs cycles
6 NADH
2 FADH
4 co2
2 GTP
Why is citric cycle called amphibollic
Both used for anabolic purposes and catabolic
What is oxaloacetate used to generate in anabolic reactions
Aspartate which can produce amino acids or purines like atp
What can citrate be used to generate
Fatty acids for storage etc
What can a ketoglutarate be used to produce
Glutamate into amino acids
What is succinyl coa importent for
Porphyrin and heme in RBCs
Which 3 enzymes in citric acid cycle are controlled
Pyruvate dehydrogenase
Isocitrate dehydrogenase
A ketoglutarate dehydrogenase
When is pyruvate dehydrogenase activated and inactivated
Active when- ADP present, a lot of pyruvate
Inactive when - a lot of acetyl coa or atp or NADH present
When is isocitrate dehydrogenase activated and inactive
Activated when - a lot of ADP which needs to be produced into ATP
Inactive when - too much ATP or NADH present
When is a ketoglutarate dehydrogenase active and inactive
Active when - ADP present (low energy),
Inactive when - too much coa , succinyl , atp or dehydrogenase
How is acetyl coA turned into fat storage for energy
Converted to fatty acids then into triglycerides with the help of citrate
Why can triglycerides be used for energy storage
Because when broken down (oxidised) the fatty acids can be converted back into acetyl coA for the citric acid cycle
