TCA cycle/ETC/ATP synthase Flashcards
Where does the Krebs Cycle occur in the cell?
The Krebs Cycle occurs in the mitochondrial matrix.
What is the transition step that precedes the Krebs Cycle, and what are its products?
The transition step converts pyruvate (from glycolysis) into acetyl-CoA in the presence of oxygen. This process also produces NADH and CO2.
What is the starting substrate of the Krebs Cycle, and how is it formed?
The starting substrate is citrate, which is formed by the combination of acetyl-CoA and oxaloacetate.
What is a helpful mnemonic for remembering the intermediates of the Krebs Cycle?
Citrate Is Krebs’ Starting Substrate For Making Oxaloacetate” (Citrate, Isocitrate, Alpha-ketoglutarate, Succinyl-CoA, Succinate, Fumarate, Malate, Oxaloacetate).
Which enzyme catalyzes the first step of the Krebs Cycle (formation of citrate), and how is it regulated?
Citrate Synthase catalyzes the formation of citrate. It is inhibited by ATP, NADH, citrate, and succinyl-CoA, and stimulated by ADP.
What is the function of Isocitrate Dehydrogenase, and how is it regulated?
Isocitrate Dehydrogenase converts isocitrate to alpha-ketoglutarate, producing NADH and CO2. It is inhibited by ATP and stimulated by ADP and calcium.
What are the products of the reaction catalyzed by Alpha-Ketoglutarate Dehydrogenase, and how is this enzyme regulated?
Alpha-Ketoglutarate Dehydrogenase converts alpha-ketoglutarate to succinyl-CoA, producing NADH and CO2. It is inhibited by succinyl-CoA and NADH and stimulated by calcium.
Which step in the Krebs Cycle involves substrate-level phosphorylation, and what are the products?
The conversion of succinyl-CoA to succinate by Succinyl-CoA Synthetase involves substrate-level phosphorylation, producing GTP (which is converted to ATP).
What is the role of Succinate Dehydrogenase, and where else is it found?
Succinate Dehydrogenase converts succinate to fumarate, producing FADH2. It is also known as Complex II of the electron transport chain.
What are the net products of one turn of the Krebs Cycle?
One turn of the Krebs Cycle produces 2 CO2, 3 NADH, 1 FADH2, and 1 ATP (via GTP).
What are the net products from the Krebs Cycle for one molecule of glucose (two turns of the cycle)?
For one molecule of glucose, two turns of the Krebs Cycle produce 4 CO2, 6 NADH, 2 FADH2, and 2 ATP.
How do the NADH and FADH2 produced in the Krebs Cycle contribute to ATP production?
NADH and FADH2 are used in the electron transport chain and oxidative phosphorylation to generate a large amount of ATP.
What is the primary function of the Electron Transport Chain (ETC)?
The ETC is where electrons are transferred through a series of membrane protein complexes, ultimately leading to the reduction of oxygen to water and the pumping of protons.
Where is the Electron Transport Chain located in the cell?
The Electron Transport Chain is located in the inner mitochondrial membrane.
What are the main electron donors to the Electron Transport Chain?
The main electron donors are NADH and FADH2, which are produced during glycolysis, pyruvate oxidation, and the Krebs Cycle.
Name the four main protein complexes of the Electron Transport Chain and the mobile electron carriers.
The complexes are: Complex I (NADH Dehydrogenase), Complex II (Succinate Dehydrogenase - also part of the Krebs Cycle), Complex III (Cytochrome Reductase or bc1 complex), and Complex IV (Cytochrome Oxidase). The mobile carriers are Ubiquinone (Q) and Cytochrome c.
How do electrons flow through the Electron Transport Chain?
Electrons flow from NADH to Complex I, then to Ubiquinone, to Complex III, to Cytochrome c, to Complex IV, and finally to oxygen. Electrons from FADH2 enter the chain at Complex II, then go to Ubiquinone and follow the rest of the chain.
What happens to protons during electron transport through Complexes I, III, and IV?
As electrons move through Complexes I, III, and IV, energy is released, which is used to pump protons (H+) from the mitochondrial matrix into the intermembrane space.
What is the role of oxygen in the Electron Transport Chain?
Oxygen is the final electron acceptor in the ETC. It receives electrons from Complex IV and combines with protons to form water. Oxygen’s high electronegativity is what pulls electrons through the chain
What is Chemiosmosis?
Chemiosmosis is the process where the potential energy stored in the proton gradient (higher proton concentration in the intermembrane space than the matrix) is used to produce ATP.
How does ATP Synthase produce ATP?
ATP Synthase is a protein complex in the inner mitochondrial membrane that acts as a channel for protons to flow back into the mitochondrial matrix, down their electrochemical gradient.
This flow of protons drives the rotation of parts of ATP Synthase, which catalyzes the phosphorylation of ADP to ATP.
What is Oxidative Phosphorylation?
Oxidative phosphorylation is the overall process that combines the Electron Transport Chain and Chemiosmosis.
It involves the oxidation of NADH and FADH2 (releasing electrons) and the phosphorylation of ADP to ATP (driven by the proton gradient).
Approximately how many ATP molecules are produced from one molecule of NADH through oxidative phosphorylation?
One molecule of NADH typically yields about 2.5 to 3 molecules of ATP. (The video states 3 ATP).
Approximately how many ATP molecules are produced from one molecule of FADH2 through oxidative phosphorylation?
One molecule of FADH2 typically yields about 1.5 to 2 molecules of ATP. (The video states 2 ATP).
