TCA Cycle and Oxidative Phosphorylation Flashcards
What are the prosthetic groups for the enzymes of the Pyruvate dehydrogenase complex?
E1 - TTP
E2 - lipamide
E3 - FAD
What happens in the first part of the PDH complex at E1?
Pyruvate with TPP is decarboxylated to hydroxyethyl-TPP
W/ CO2 as a product.
What happens in the second part of the pyruvate dehydrogenase complex at E2?
E2 with help of the movable lipoamide oxidizes Hydroxyethyl-TPP to an acetyl group. The acetyl group is transferred to lipoamide.
Makes a Acetyl lipoamide - which has an energy rich thioester bond
- > linked at a lysine at E1.
- > transfer catalyzed by E1
What happens in the third part of the pyruvate dehydrogenase complex at E3?
The lipoamide-acetyl group swings to a deep part of E2, the acetyl group is transferred to a CoA, a processed catalyzed by E2.
E3 oxidezes the remaining dihydroamide back to a lipoamide. This transfers to a FAD+ and then to NAD+
FAD is the prosthetic group
Acetyl-CoA the second product is made out of this.
Get NADH from this step
What regulates the PDH complex?
high [Acetyl CoA] inhibits E2
Allosterically regulated by reverse phosphorylation -> similar to glycogen synthase
Products increase the phosphorylation of PDH
Accumulation of ADP and pyruvate activates phosphatases.
The first step of the CAC catalyzed by citrate synthase mainly includes which events?
The condensation of oxaloacetate and the acetyl group from the Acetyl-CoA giving citrate
After citrate is formed in the TCA cycle what is the next step?
The citrate molecule is isomerized to isocitrate to prepare for the first decarboxylation event.
Isocitrate dehydrogenase catalyzed what step of the TCA cycle?
Isocitrate decarboxylation to a-ketogluterate with the release of a CO2 and a NADH
Redox
Rate limiting
Allosteric stimulated by ADP
After the first decarboxylation event a-ketogluterate dehydrogenase catalyzes what?
Release of NADH and CO2 and formation of Succinyl-CoA.
This step is similar to PDH because both are decarboxylations of an a-ketoacid and create a thioester bond with a CoA
What’s unique about the succinyl-CoA synthetase step of the TCA cycle?
It is the only step of TCA that directly gives off a high energy compound, GTP
And Succinate
After the formation of Succinate from Succinyl-CoA in the TCA cycle, what energy molecule is release and the product of succinate dehydrogenase?
The redox rxn between succinate and fumerate by succinate dehydrogenase gives off a FADH2
No change in carbon number between the molecules.
It is then turned into Malate by fumerase
Fumerase turns Fumerate into Malate. What happens next in the TCA cycle?
Malate into Oxaloacetate by malate dehydrogenase, releasing a NADH
At this point the cylce is ready to restart.
Not a favorable reaction. The reaction is driven by the use of the products, oxaloacetate and NADH
What doess it mean if there is a build up of NADH?
It means that the CAC isnt running. The excess of NADH means a build up of potential energy.
The Citric Acid Cycle is regulated at PDH, isocitrate dehydrogenase, and a-ketogluturate dehydrogenase.
The PDH is stimulated with ADP and pyruvate and downregulated by ATP, acetyl CoA and NADH
Isocitrate dehydrogenase is allosterically stimulated by ADP and negatively regulated by ATP and NADH
A-ketogluturate dehydrogenase is only negatively regulated by ATP, succinylcholine CoA and NADH.
-> similar to PDH, also allosterically inhibited by it’s products.
Inhibiting the cycle at isocitrate dehydrogenase leads to a build up of citrate. This citrate goes back and inhibits what other metabolic processes?
What else can citrate go?
Glycoylsis at phosphofructokinase.
Citrate can be used to make fatty acids and sterols.
The TCA cycle is stoped, the intermediates can go on to other cycles and processses. What are these intermediates and where do they go?
Citrate -> shuts down glycolysis and goes on to make fatty acids and sterols
a-ketogluturate goes on to make glutamate and other amino acids, mostly purines
Succinyl-CoA will make porphyrins, heme and chlorophyll
Oxaloacetate can go into gluconeogenesis and be turned into glucose or Aspartate into pyrimidines and even purines.
You sleep all night and wake up and go exercise, what metabolic pathways are active?
Glycolysis
CAC
-> low ATP
Oxidative phosphoylation
Fatty acid oxidation
Amino Acids that can be converted into Pyruvate
Alanine, serine, glycine, threonine, cysteine and tryptophan
Amino Acids that can be converted into oxaloacetate
Aspartate and asparagine
Amino Acids that can be converted into alpha-ketogluturate
Glutamate, glutamine, proline, histidine, arginine
Amino Acids that can be converted into fumerate
Phenylalanine and tyrosine
Amino Acids converted to succinyl-CoA
Methionine, isoleucine and valine
Amino Acids that can be converted into Acetyl-CoA
Leucine, isoleucine, lysine, phenylalanine, tyrosine, tryptophan and threonine
What is the function of complex I?
FMN and Fe-S are prosthetic groups
First point of entry for NADH, e- transferred to the Q
Protons pump out, 4.
Protrude in matrix and is integral
What happens at complex II of the electron transport chain?
FADH2 transfers its electrons to Q, reducing Q.
Complex II does not pump protons
FADH2 does not leave the complex
FAD and Fe-S are prosthetic groups
Complex III of ETC does what?
Retrieves electrons from Q. 2 protons pump for each electrons. The electrons move on to Cytochrome C
The prosthetic groups are heme bh, Heme Bl and Heme c1. And Fe-S
What is unique about Complex IV?
The last complex on the ETC before ATP synthase. Electrons transfer to O2 breaking the peroxide bonds and forming water.
Protons are pumped to the matrix
4 protons for pumping, 4 protons for water forming
