TCA Cycle Flashcards
What can deficiency in pyruvate dehydrogenase lead to?
Lactic acidosis because pyruvate will be reduced to lactate to reoxidise H carriers.
What reaction in carbohydrate metabolism is sensitive to vitamin B deficiency?
Pyruvate –> Acetyl~coA
PDH requires coenzymes which are derived from B vitamins.
Give three molecules which activate and three molecules which inhibit the conversion of Pyruvate to acetyl~coA.
Activate: Pyruvate, NAD+, ADP, Insulin
Inhibit: acetyl~coA, NADH, ATP
What enzyme catalysts the reaction of Pyruvate to acetyl~coA? Where does this reaction occur?
Pyruvate dehydrogenase. It occurs in the mitochondria.
What are three things which are produced from the TCA cycle?
Bio synthetic precursors, energy in the form of ATP and reducing power (NADH/FADH2)
State two ways in which the TCA cycle is regulated.
By energy availability, allosteric regulation.
Can the TCA cycle function in the absence of O2?
No, because it is an oxidative pathway and it requires H carriers which need to be reoxidised.
What is the difference between substrate level and oxidative phosphorylation?
In substrate level, the phosphate molecule is passed directly from the substrate to ADP to form ATP.
In oxidative phosphorylation this is coupled to the electron transport chain. This is the major process when large amounts of ATP are required.
What does the electron transport chain utilise to synthesise ATP?
Energy in the form of reducing power held by H carriers which are reoxidised.
Briefly describe what happens in the electron transport chain.
Electrons from NADH (or other H carrier) are carried through proton translocating complexes to Oxygen. Protons are moved into the inter membrane space in the mitochondria, and this gives an ion gradient (pmf) across the inner membrane.
Why are protons forced through ATPase complex?
The inner membrane of mitochondria is impermeable to H+ ions, and so the only way for the protons to move down the concentration gradient is through ATPase.
How does the electron transport chain help us to maintain our body temperature?
During this process, a lot of energy is lost as heat.
What is the regulator for Oxidative phosphorylation?
There is only a limited amount of ADP/ATP so when ATP is high there is little ADP and so no substrate for the reaction and therefore it cannot occur. ATP acts as a regulator. Inhibition will lead to high [H+] which then prevents electron pumping.
Why do CO and CN act as inhibitors of oxidative phosphorylation?
These bind to haem groups in the proton translocating complexes, which means they cannot carry oxygen and there is nowhere for the electrons to go. This means no H+ pumping and therefore no ATP synthesis.
What is the cause of uncoupling of the electron transport chain and oxidative phosphorylation?
Uncouplers make the inner membrane in the mitochondrion permeable to H+ which means that they do not move through ATP synthase to produce ATP. Excess energy is lost as heat.
