TCA cycle Flashcards
How are mitochondria and bacteria similar in relation to size and shape?
bacillus rod shaped, ranging between 1 and 10 microns in length.
How are mitochondria and bacteria similar in relation to replication?
Both replicate via binary fission
How are mitochondria and bacteria similar in relation to type of DNA?
Both contain circular DNA plasmids
How are mitochondria and bacteria similar in relation to ribosome and protein synthesis?
Mitochondria carry their own ribosomes to make proteins which looks more like bacterial ribosomes
How are mitochondria and bacteria similar in relation to membranes?
Both inner and outer membrane w/ other membrane with similar proteins like porins
Where does the conversion for pyruvate to acetate occur?
Mitochondrial matirx
What transports pyruvate across the mitochondrial membrane?
A pyruvate transporter (MPC) transports pyruvate across the impermeable inner mitochondrial membrane.
What does the mitochondria contain to increase its surface area?
Cristae
Where does the TCA cycle occur?
In the mitochondrial matrix
Describe the link reaction between glycolysis and TCA cycle.
Eg reactants products and enzyme
Pyruvate to ACetyl-CoA via pyruvate dehydrogenase
NAD+ turns to NADH and CoA-SH turns to CO2
Pyruvate dehydrogenase is a multil-enzyme complex
Explain the steps.
E1: Pyruvate dehydrogenase which uses thiamine pyrophosphate (TPP) as its prosthetic group.
E2: Dihydrolipoyl transacetylase which uses lipoamide and coenzyme A (also known as CoA-SH) as its prosthetic groups.
E3: Dihydrolipoyl dehydrogenase which uses flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NAD+) as its cofactors.
Describe the E1 step in pyruvate dehydrogenase
E1: Pyruvate dehydrogenase which uses thiamine pyrophosphate (TPP) as its prosthetic group.
Describe the E2 step in pyruvate dehydrogenase
E2: Dihydrolipoyl transacetylase which uses lipoamide and coenzyme A (also known as CoA-SH) as its prosthetic groups.
Describe the E3 step in pyruvate dehydrogenase
E3: Dihydrolipoyl dehydrogenase which uses flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NAD+) as its cofactors.
Name the 3 prosthetic groups used for pyruvate dehydrogenase
TTP
Lipoate
FAD
What is TTP needed for in pyruvate dehydrogenase
Required for pyruvate decarboxylation
What is lipoate needed for in pyruvate dehydrogenase
Required for the transfer of the acetyl group to Coenzyme A
What is FAD needed for in pyruvate dehydrogenase
Required for the regeneration of the oxidised for of lipoate
Why do enzyme complexes exist?
To speed up reactions
How many steps are in the TCA cycle?
How many carbons are lost each turn?
8 steps
loses 2 carbons each turn
Describe the first step of the TCA cycle
What is the type of the reaction?
What drives the reaction?
Citrate synthase- condensation
Acetyl-CoA + Oxaloacetate -> Citrate
with Citrate synthase and H20 -> CoA-SH
Driven by hydrolysis of the thioester
Describe the TCA cycle- Step 2
What is the reaction type
What is the cofactor?
How many steps is this and what is the name of the intermediate?
Aconitase
Isomerisation reaction
FE-S complex= cofactor
2 step reaction/ intermediate= cis-aconitate
Citrate<=>isocitrate
Describe the third step of the TCA cycle
What type of reaction?
What is the cofactor?
How many steps and what is the intermediate ?
Isocitrate dehydrogenase
Isocitrate-> Oxalosuccinate ( NAD+ to NADH +H+)
AND oxalosuccinate -> alpha-ketoglutarate (H+-> CO2)
Reaction= oxidative deacarboxylation
Cofactor= NAD+
2 steps intermediate = oxalosuccinate
Describe the 4th step in the TCA cycle
What is the reaction type
What is the cofactor
Alpha-ketoglutarate dehydrogenase
Alpha-ketoglutarate -> succinyl-CoA
( CoASH -> CO2 and NAD+ -> NADH+h+)
reaction type= oxidative decarboxylation
Cofactor= NAD+ and CoA-SH
Describe the 5th step of the TCA cycle
What is the reaction type
What is the cofactor
Succinyl CoA synthetase
or
Succinate thiokinase
Succinyl-CoA<=> Succinate ( GDP+Pi-> GTP CoA-SH)
Reaction type=substrate level phosphorylation
Cofactor= GDP .The GTP can be used to form ATP (nucleoside diphosphate kinase). ATP and GTP are energetically equivalent.
Describe the 6th step of the TCA cycle
What is the cofactor
What is the reaction type?
What is significant about the enzyme?
Succinate<=> Fumerate Succinate dehydrogenase (FAD->FADH2)
Reaction Type=oxidative dehydrogenation
Cofactor= FAD reduced to FADH2
Enzyme is the only Krebbs one contained in the inner mitochondrial membrane. Active site faces the mitochondrial matrix
Describe Step 7 in the TCA cycle
What is the reaction type?
Fumarate<=>L-malate (H20)
Fumarase
Reaction type: catalyses a stereospecific trans addition of a hydrogen atom and a hydroxyl group
Describe step 8 of TCA cycle
What is the cofactor?
What is the reaction type?
What drives the reaction forwards?
L-malate <=> oxaloactate (NAD+-> NADH + H+)
malate dehydrogenase
Reaction type= oxidative dehydrogenation
Cofactor= NAD+
Reaction driven by OAA depletion
What is the structure of Acetate?
CH3-Coo^-
What is the structure of Acetyl-CoA?
CH3-C=O-S-CoA
What is the structure of pyruvate?
O^- -C=O-C=O-CH3
Name all 8 enzymes in the Krebs cycle
Citrate synthase Aconitase Isocitrate dehydrogenase α-ketoglutarate dehydrogenase Succinyl CoA synthetase Succinate dehydrogenase Fumarase Malate dehydrogenase
How many NADH needed for production of acetyl Co-A?
How many NADH, FADH2 and GTP/ATP from one turn of the TCA cycle?
1 NADH for the production of acetyl-CoA
3 NADHs from one turn of the TCA cycle
1 FADH2 from TCA
1 GTP (ATP) directly from the TCA cycle
What is the net production of ATP from glycolysis and the TCA cycle?
Glycolysis generates 8 ATP
TCA cycle generates 30 ATP for 2 pyruvates entering the TCA cycle
Total 38 net ATPs
