TCA cycle and ETC Flashcards
What is the TCA cycle?
The common metabolic pathway for all food molecules: carbohydrates, AA’s and fatty acids.
Where does the TCA cycle occur?
In the mitochondrial matrix.
What molecules are produced in every turn of this cycle?
3 NADH, 2 CO2, 1 FADH2 and 1 GTP.
What happens to pyruvate from glycolysis in this cycle?
O2 present so not converted to lactate. Instead, converted to acetyl CoA in mitochondrial matrix. Pyruvate dehydrogenase enzyme does this.
What happens when acetyl CoA enters the TCA?
2 acetyl CoA’s enter and 2CO2’s leave.
What are the intermediates of the TCA?
Citrate, isocitrate, alpha-ketoglutarate, succinyl CoA, succinate, fumarate, malate and oxaloacetate.
How is entry into the TCA controlled?
If the cell needs energy, pyruvate is broken down to acetyl CoA. If not, pyruvate dehydrogenase does not work.
What regulates isocitrate dehydrogenase?
ATP and NADH negatively regulate, ADP positively regulates. Citrate builds up if this enzyme is blocked. Citrate goes to cytoplasm and tells PFK1 to stop glycolysis.
What regulates alpha-ketoglutarate dehydrogenase?
ATP, NADH and succinyl CoA negatively regulate. If this enzyme is blocked alpha-ketoglutarate switches to making AA’s.
Which enzyme converts pyruvate to oxaloacetate?
Pyruvate carboxylase. Only active when acetyl CoA is present.
Acetyl CoA enters the TCA cycle. Where does it come from?
It is formed from pyruvate or fatty acids.
Does the TCA cycle produce ATP?
No, not directly. Passes electron carriers to ETC.
What is the final stage of respiration and where does this occur?
ETC. Occurs in the mitochondrial matrix and intermembranous space.
What is the order of the 4 ETC complexes?
NADH-Q oxidoreductase, Succinate Q-reductase, Q-cytochrome c oxidoreductase and cytochrome c oxidase.
Why are protons pumped across the membrane?
To set up a protein gradient in the inner membrane of the mitochondria.
What is the function of complex 1 of the ETC?
NADH-Q oxidoreductase: reduces NADH and passes electrons to ubiquinone to make ubiquinol. Pumps H+ ions to the intermembranous space.
What is the function of complex 2 of the ETC?
Succinate-Q reductase: reduces FADH2 and passes the electrons to ubiquinol.
What is the function of complex 3 of the ETC?
Q-Cytochrome c oxidoreductase: takes electrons from ubiquinol and passes them to cytochrome C. Pumps H into the intermembranous space.
What is the function of complex 4 of the ETC?
Takes electrons from cytochrome c and passes them to oxygen. Pumps protons into the intermembranous space.
What force allows the gradient in the ETC to work?
Proton motive force.
What happens when protons come back into the mitochondria through ATP synthase?
The beta subunit generates ATP. Energy is released which turns ADP+Pi into ATP.
What is the mechanism that allows ATP synthase to generate ATP?
Binding-change mechanism.
