BCHM 270 Midterm Exam Questions and An swers TCA Cycle Step 1 - Correct Answer ✔️✔️-*citrate synthase* oxaloacetate + Acetyl = Citrate + CoA TCA Cycle Step 3 - Correct Answer ✔️✔️-*isocitrate dehydrogenase* isocitrate --> alpha -ketoglutarate + *NADH* + CO2 TCA Cycle Step 4 - Correct Answer ✔️✔️-*alpha -ketogluterate dehydrogenase* alpha -ketoglutarate --> Succinyl CoA + *NADH* + CO2 TCA Cycle Step 5 - Correct Answer ✔️✔️-*Succinate thiokinase* Succinyl CoA --> Succinate + *GTP* -cleaves high energy thioester bond (S -CoA) to drive reaction forward TCA Cycle Step 6 - Correct Answer ✔️✔️-*succinate dehydrogenase* succinate --> fumarate + *FADH2* TCA Cycl e Step 8 - Correct Answer ✔️✔️-*malate dehydrogenase* L-Malate --> Oxaloacetate + *NADH* Direction of electron flow in electron transport chain - Correct Answer ✔️✔️-from compounds with lower redox potentials to compounds with higher redox potentials (low free energy to high free energy) which is used to move protons from the matrix into the inter membrane space to generate the chemiosmotic gradient ATP synthase activity - Correct Answer ✔️✔️-Flow of protons back into the matrix causes movement within the enzy me that creates kinetic energy which cause the beta subunits to cycle between 3 conformational states to bind ADP to Pi. Proton motive force provides the energy to allow it to cycle and release ATP. NADH and FADH2 difference - Correct Answer ✔️✔️-- NADH pro duces 3 ATP as its electrons are passed to complex 1 and FADH2 produces 2 ATP as its electrons are passed to complex 2 (pumps fewer protons) - Only NADH produced locally can produce 3 ATP as the inner mitochondrial membrane lacks an NADH transporter and th erefore its electrons use two shuttle systems in the cytoplasm Uncoupling proteins - Correct Answer ✔️✔️-brown fat is used by infants to generate heat which is done by uncoupling proteins in the ETC which bypass ATP synthase and allow protons to reenter the the matrix without generating ATP (energy dissipated as heat rather than ATP). Oligomycin - Correct Answer ✔️✔️-Blocks proton channel in ATP synthase. Gradient becomes too great and thus no ATP made. Synthetic uncouplers - Correct Answer ✔️✔️-Allows electro ns in ETC to move through the membrane without pumping protons. Heat is produced. What is an enzyme? - Correct Answer ✔️✔️-Typically globular proteins with multiple domains that act as catalysts for chemical reactions. Can increase reactions rates by 103-108 times. What do enzymes do? - Correct Answer ✔️✔️-Catalyze a reaction by binding to substrate and lowering activation energy which is done by enzyme stabilization of the transition state.
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