LEC 7 Flashcards
What is the first stage of cellular respiration? And what does this stage include?
Stage #1 - Acetyl-CoA Production. This stage includes glycolysis (and even glycogen breakdown). It includes Acetyl CoA production from amino acids to pyruvate, glycolysis to pyruvate, and fatty acid oxidation to acetyl CoA.
All of these pathways produce NADH/FADH2.
What is the 2nd stage of cellular respiration?
Citric Acid Cycle. Acetyl-CoA will feed the citric acid cycle and Acetyl-CoA will become CO2. Acetyl-CoA is being oxidized. The Citric Acid Cycle will also reduce electron carriers, NAD+ and FAD+. Both stage 1 and 2 will carry out substrate level phosphorylation (one of the reaction’s steps will be ATP).
What is the 3rd stage of cellular respiration?
Oxidative Phosphorylation -> takes all of the reduced electron carriers and oxidizes them through a process called the electron transport chain which will then be used to make a proton gradient to drive ATP synthesis and this will use oxygen to do that.
What is the end result of the PDC reaction?
It makes Acetyl CoA from pyruvate. Pyruvate, the alpha-keto acid, is going to lose the carboxyl group as CO2 (decarboxylation reaction) and turn into Acetyl-CoA. The carboxyl group will be displaced by CoA. Delta G in this reaction is less than 0 so it is irreversible and a regulatory step.
Where is the energy of the PDC reaction conserved? Where does the energy from the PDC reaction come from?
???
What coenzymes are found in E1, E2, and E3? Where do steps of the decarboxylation of pyruvate and production of acetyl-CoA and NADH occur? How are the coenzymes involved?
In E1 (pyruvate Dehydrogenase) the coenzyme, TPP, is permanently attached. Pyruvate Dehydrogenase’s function is to decarboxylate pyruvate.
In E2 (Dihydrolipoamide Transacetylase) the coenzyme are a) Lipoate which is permanently attached and b) CoA (which can come on and off). E2’s function is to carry carbons and electrons. E2 also produces Acetyl-CoA.
E3, aka Dihydrolipoamide Dehydrogenase, has FAD permanently attached and NAD+ which can come on and off. E3 produces NADH.
What are the allosteric regulators and competitive inhibitors of the PDC reaction?
Acetyl-CoA and NADH are competitive inhibitors. Acetyl-CoA will actually occupy (when there is high enough [] of Acetyl-CoA) the active site of E2 and E3 in the case of NADH.
ADP and Pyruvate will inhibit the PDH kinase, which means PDC will stay active. Thus, when the cell increases it’s production of pyruvate, PDC can do it’s job to convert pyruvate to Acetyl-CoA.
What role does PDH kinase and PDH phosphatase play in the regulation of PDC?
????
What is PDCD? Explain why PDCD leads to elevated lactate, alanine, and pyruvate in the blood. What are possible treatments for this condition?
????
Can you think of an advantage of forming a “complex” of enzymes rather than having enzymes functioning independent of each other?
Since the intermediates do not have other fates splitting off into other pathways it makes sense for the substrate to stay within the complex through completion and, mistakes can happen in intermediates thus, having the intermediates stay within the complex through completion will prevent mistakes from happening.
What does PDH kinase do?
It phosphorylates Pyruvate Dehydrogenase Complex and in doing so makes PDC inactive. The kinase is called PDH kinase. NADH and Acetyl CoA, which are competitive inhibitors of PDC, will active the kinase, which makes sense since PDH will inactivate Pyruvate Dehydrogenase.
Why is pyruvate dehydrogenase complex so tightly regulated?
Because the production of acetyl-CoA can’t go backwards
PDCD is a serious condition. Initial diagnosis of this condition requres blood work in which a suspecting physician will look for certain makers within blood that, if present, will lead to additional testing. Name two metabolites that may be elevated in these patients.
Pyruvate, lactate, and Alanine. Pyruvate will go up and pyruvate will be held in equilibirum with lactate and alanine.
Explain how muscle contration will affect PDC.
When you start contracting your muscles, Ca+ levels will go up, Ca+ will activate the PDC phosphatase, and the activation of the phosphatase will DEphosphorylate PDC making the PDC active. Thus, with an active PDC, it will lead to a production of Acetyl-CoA which then can feed the citric acid cycle which can then feed oxidative phosphorylation which then can make ATP.
