TCA Cycle and Electron Transport Chain Flashcards
What are names for the TCA cycle?
TCA cycle, krebs cycle, citric acid cycle
What is oxidative phsophsorylation?
The oxidation of NADH and FADH2 in the electron transport chain provide energy for the phosphorylation of ADP to ATP in the protonmotive pump (ATP Synthase)
Where does TCA occur?
Mitochondria!
Where does oxidative phosphorylation occur, specifically?
In the mitochondria, across the inner membrane. The hydrogen ion concentration is greatest in the intermembrane space (between membranes) and lower in the inner mitochondrial matrix. The electron transport chain pushes hydrogen ions into the intermembrane space. The proton pump pulls hydrogen ions back into the inner mitochondrial matrix and uses the energy to phosphorylate ADP –> ATP
How many ATP is oxidation of NADH worth?
2.5. Except in the NADH produced by glycolysis, these are only worth 1.5 because one ATP is used in their transport.
How man ATP is oxidation of FADH2 worth? Why is it different than NADH?
1.5. FADH donates its electrons to Complex 2 in the electron transport chain. Complex 2 does not generate any energy but merely passes electrons to Coenzyme Q. Since Complex 1, which was skipped, generates enough energy to push 4 H+ ions across the inner membrane, FADH is only worth 6 H+. It takes 4H+ to generate 1 ATP in ATP synthase
What is ATP synthase?
The proton pump! It uses the hydrogen ion gradient between the intermembrane space (high H+) and the inner mitochondrial matrix (low H+) to provide energy for the phosphorylation of ADP to ATP. There are three major components: an H+ acceptor domain facing the intermembrane space, a linkage domain in the membrane, and a rotor domain which binds ADP and produces ATP in the inner mitochondrial matrix.
Draw the electron transport chain
The electron transport chain occurs between the inner mitochondrial matrix and the intermembrane space. The intermembrane space has a higher concentration of H+, but we’re pumping against the concentration gradient here so H+ is pumped into the intermembrane space, and then let back into the mitochondrial matrix through the proton pump. NADH is oxidized to NAD+ and donates its two electrons to Complex 1. Complex 1 uses a series of redox centers, each perfectly aligned for electron jumping and each with an increasing binding affinity, to generate energy and ultimately drop the electrons off with Coenzyme Q. The energy produced here is adequate to push 4 H+ across.
Complex 2 inputs FADH2 and transfers electrons to Coenzyme Q without generating energy.
Coenzyme Q takes the electrons to Complex 3, where a similar redox center electron jumping occurs. One electron is recycled at Complex 3. Energy here is adequate to push 2H+ across. Cytochrome C receives the remaining electron and takes it to Complex 4. Complex 4 uses the electron’s energy to create water from O2 and H+, while also pushing 4H+ across.
Draw ATP Synthase’s mechanism of action
ATP synthase has a H+ binding domain, which has 12 C subunits. Each of these subunits is able to bind a single hydrogen ion. After binding H+, the binding domain twists. This twist sort of “winds up” the rotor domain. After 3 H+ bind, enough twisting has occurred to energize the transformation of ADP to ATP. But ATP now needs to leave the rotor domain. This requires another H+ to bind the binding domain. So it takes a total of 4H+ ions to pass through the channel to create a single ATP. The used H+ ions end up in the inner mitochondrial matrix, where the H+ concentration is lesser.
What is the krebs cycle used for?
Production of ATP (mostly indirectly, although it does produce 1 GTP for each cycle). Krebs cycle produces 3 NADH, 1 FADH, and 1 GTP. It recycles oxaloacetate and uses Acetyl CoA as inputs.
What are the inputs to the krebs cycle?
Acetyl CoA and Oxaloacetate
How many FADH2 and NADH does one glucose provide through the krebs cycle?
One glucose produces 2 pyruvates. Each pyruvate is turned into acetyl CoA, producing one NADH. Then, in the TCA cylce, each acetyl CoA produces 3 NADH, 1 GTP, and 1 FADH2. That ends up summing (since we have 2 acetyl CoAs) to 8NADH, 2FADH2, and 2 GTP. BUT! In glycolysis you also produce 2NADH (which are less efficient due to transport, only worth 1.5 ATP each) and 2 ATP. This gives you a total of 30 ATP from one glucose molecule.
How is acetyl CoA formed?
Acetyl CoA can be formed from pyruvate dehydrogenase complex acting on pyruvate. This generates a CO2 and transforms a NAD to NADH. Acetyl CoA can also come from acetate, amino acids, fatty acids, and ketone bodies
What does alphaketoglutarate dehydrogenase do?
It turns alphaketoglutarate into succinyl-CoA. Additional inputs are CoAsh, NAD. Additional outputs are NADH, CO2
What does isocitrate dehydrogenase do?
Turns isocitrate into alpha-ketoglutarate. Additional inputs are NAD. Additional outputs are NADH and CO2
What does fumarase do?
Fumarase takes you from fumarate to malate. It has an additional input of a water molecule.
What does malate dehydrogenase do?
Malate dehydrogenase takes you from malate to oxaloacetate. Malate dehydrogenase turns an NAD+ into an NADH
What does citrate synthase do?
Citrate syntahse combines Acetyl Coa with Oxaloacitate to form citrate. CoA-SH is released.
At what steps in the TCA cycle are carbon dioxide molecules released?
In the preparation step from Pyruvate to Acetyl CoA, in isocitrate –> (isocitrate dehydrogenyase) –> alpha-ketoglutarate, in alpha-ketoglutarate –> (alpha-ketoglutarate dehydrogenase) –> succinyl CoA, and in malate –> (malate dehydrogenase) –> oxaloacetate
What does aconitase do?
takes you from citrate to isocitrate
What does succinate thiolkinase do?
takes you from succinyl CoA to succinate. It generates a GTP and release CoA-SH
