BICH Exam 2

What is the TCA cycle?

A crucial pathway in aerobic respiration central for recovering energy, yielding approximately 36 ATP.

What is the role of pyruvate in the TCA cycle?

Pyruvate is converted to acetyl-CoA to enter the TCA cycle.

What are the main products of the TCA cycle?

The TCA cycle produces CO₂, NADH, and FADH₂.

What is the significance of NADH and FADH₂?

They carry electrons to the electron transport chain for ATP production.

What is oxidative phosphorylation?

A process that couples electron transfer to a proton gradient to drive ATP synthesis.

What occurs during glycolysis?

Glycolysis breaks glucose into pyruvate, generating 2 ATP per glucose molecule.

What is the function of the Pyruvate Dehydrogenase Complex (PDHC)?

PDHC converts pyruvate into acetyl-CoA, linking glycolysis to the TCA cycle.

What are the three enzymes of PDHC?

E1: Pyruvate Dehydrogenase, E2: Dihydrolipoyl Transacetylase, E3: Dihydrolipoyl Dehydrogenase.

What cofactors are required for PDHC?

TPP, lipoic acid, CoA, FAD, and NAD+.

What happens to pyruvate during the PDHC reaction?

Pyruvate is oxidatively decarboxylated to form acetyl-CoA.

What does the TCA cycle aim to achieve?

The complete oxidation of glucose to CO₂ involves 24 electrons.

How are electrons extracted in the TCA cycle?

Electrons are extracted and stored as NADH and FADH₂.

What inhibits the Pyruvate Dehydrogenase Complex?

High levels of NADH, acetyl-CoA, and ATP inhibit PDHC.

What activates PDHC?

Ca²⁺ and ADP activate PDHC, indicating a need for energy production.

What is beriberi?

A disease caused by vitamin B1 (Thiamine) deficiency.

What role does lipoic acid play in PDHC?

Lipoic acid helps transfer intermediates within the enzyme complex.

How is GTP produced in the TCA cycle?

Through substrate-level phosphorylation when converting succinyl-CoA to succinate.

What is the role of citrate synthase?

It catalyzes the first reaction of the TCA cycle by combining acetyl-CoA with oxaloacetate.

How is isocitrate formed from citrate?

Through a reversible dehydration-rehydration step mediated by aconitase.

What does isocitrate dehydrogenase produce?

It oxidizes isocitrate to α-ketoglutarate while producing NADH and releasing CO₂.

What energy carriers are produced in the TCA cycle?

3 NADH, 1 FADH₂, and 1 GTP per turn of the cycle.

What is the regulatory role of calcium ions (Ca²+) in the TCA cycle?

Ca²+ activates key enzymes such as isocitrate dehydrogenase.

What is a significant characteristic of the TCA cycle regarding substrate?

It can produce metabolic intermediates for amino acid synthesis.

What is the significance of the glyoxylate cycle?

It allows certain organisms to convert acetyl-CoA into glucose.

What happens in the electron transport chain (ETC)?

Electrons from NADH and FADH2 are transferred through complexes to generate a proton gradient.

What enzyme synthesizes ATP using the proton gradient?

ATP synthase.

What are reactive oxygen species (ROS)?

Byproducts of the electron transport chain that can cause cellular damage.

How does the proton gradient contribute to ATP synthesis?

It drives protons back through ATP synthase, facilitating ATP production.

What reactive species are produced by the electron transport chain?

Superoxide radicals, hydrogen peroxide, and hydroxyl radicals.

What effect do complex inhibitors have on the ETC?

They block electron transport, preventing ATP production.

What are uncouplers in the context of oxidative phosphorylation?

Agents that dissipate the proton gradient as heat instead of using it for ATP synthesis.

How much ATP does NADH and FADH₂ generally yield?

NADH yields about 2.5 ATP, while FADH₂ yields about 1.5 ATP.

What happens during ATP export from mitochondria?

Each ATP exported costs one additional proton.

What is the role of the Malate-Aspartate shuttle?

It transfers electrons between the cytosol and mitochondria yielding 2.5 ATP per NADH.

What is the function of the Glycerophosphate shuttle?

Transfers electrons from cytosolic NADH to FADH₂ producing 1.5 ATP.

What are the effects of Oligomycin?

It inhibits ATP synthesis by blocking the ATP synthase F₀ subunit.

What essential vitamins are necessary for TCA cycle function?

Vitamins B1, B2, B3, and biotin are vital for proper function.

What metabolic pathways interact with the TCA cycle?

Carbohydrate, fat, and protein metabolism are linked to the TCA cycle.

What does pyruvate carboxylase do?

Converts pyruvate to oxaloacetate and is activated by acetyl-CoA.

What condition results from arsenic poisoning?

Inactivation of lipoamide, a key cofactor in PDHC.

How do vitamin deficiencies impact metabolic pathways?

They can lead to disorders affecting energy balance and metabolism.

What is the significance of metabolic intermediates from TCA?

They serve as precursors for various biosynthetic processes.

How is ATP produced during the TCA cycle?

Through substrate-level phosphorylation during the conversion of succinyl-CoA.

How does the regulation of PDHC depend on energy state?

High NADH and acetyl-CoA inhibit, while low levels activate PDH.

How do the ETC complexes contribute to the proton gradient?

They pump protons into the intermembrane space during electron transport.

What evidence suggests the presence of supercomplexes in the ETC?

They improve electron transfer efficiency and reduce ROS formation.

What is a symptom of cyanide poisoning?

Sudden collapse and cherry-red skin due to oxygen retention in blood.

What is the outcome of ATP synthesis after one full rotation of ATP synthase?

Three ATP molecules are synthesized after 360° rotation.

What factors affect regulation of the TCA cycle?

Energy state, substrate availability, and product inhibition.

What is the main purpose of the electron transport chain?

To generate a proton gradient that enables ATP synthesis.

How does ATP-ADP translocase function?

It transports ATP out of the mitochondria and ADP into the mitochondria.

What is an anaplerotic reaction?

A reaction that replenishes TCA cycle intermediates.

What role does citrate play in metabolism?

It is a precursor for fatty acids and cholesterol.

What effect do excessive CO₂ levels have on the TCA cycle?

They can inhibit the cycle and signal a high energy state.

How can TCA cycle intermediates be used in biosynthesis?

They can generate amino acids, fatty acids, and glucose.

What inhibits citrate synthase?

ATP, NADH, and Succinyl-CoA inhibit citrate synthase indicating high energy states.

What is the proton motive force?

The potential energy stored in the electrochemical gradient of protons.

What happens during the last stage of the TCA cycle?

Oxaloacetate is regenerated while releasing 2 CO₂ molecules.

What do antioxidants do in the context of ROS?

They neutralize reactive oxygen species to protect cells.

What is essential about the TCA cycle for cellular metabolism?

It integrates multiple metabolic pathways and is crucial for energy production.

What role does the Aconitase enzyme play in the TCA cycle?

It catalyzes the isomerization of citrate to isocitrate.

What is the overall reaction of the TCA cycle?

Acetyl-CoA + 3NAD+ + FAD + GDP + Pi + 2H2O → 2CO2 + 3NADH + FADH2 + GTP + CoA + 3H+.

How do metabolic intermediates affect the TCA cycle’s progression?

High concentrations of intermediates can slow down or inhibit the cycle.

What is the membrane potential, and why is it important for mitochondrial function?

It's crucial for cellular viability as it drives ATP synthesis.

How can exercise influence TCA cycle activity?

Exercise increases glycolysis and TCA activity to meet energy needs.

What are the consequences of high fructose corn syrup consumption on metabolism?

It promotes fat synthesis over energy production.

What is the effect of hypoxia on the respiratory chain?

It can impair electron transport and reduce ATP synthesis.

What is an essential feature of the succinate dehydrogenase enzyme?

It's directly linked to the electron transport chain as Complex II.

What is the final electron acceptor in the ETC?

Oxygen (O2) is the final electron acceptor in the electron transport chain.

What are the clinical implications of understanding the TCA cycle?

Insights into metabolic disorders and their treatment approaches are gained.

What type of reaction utilizes CoA in the TCA cycle?

Acetyl-CoA formation and subsequent reactions depend on CoA.

How does glucose convert to energy using the TCA cycle?

Glucose is metabolized to pyruvate, which then enters the TCA cycle as acetyl-CoA.

What is the role of α-ketoglutarate in the TCA cycle?

α-ketoglutarate is an intermediate that links energy production to amino acid synthesis.

How does the TCA cycle contribute to carbon skeletons for biosynthesis?

The TCA cycle provides intermediates that serve as building blocks for amino acids, nucleotide synthesis, and other biosynthetic pathways.

What is succinyl-CoA's role in the TCA cycle?

Succinyl-CoA is a key intermediate that leads to GTP production through substrate-level phosphorylation.

How does the TCA cycle help regulate the energy supply in the cell?

It adjusts the flow of substrates based on energy needs, ensuring efficient ATP production.

What are the primary functions of FAD in the TCA cycle?

FAD acts as an electron acceptor, becoming FADH₂ during the oxidation of succinate to fumarate.

What role does fumarase play in the TCA cycle?

Fumarase catalyzes the reversible hydration of fumarate to malate.

How is oxaloacetate regenerated in the TCA cycle?

Oxaloacetate is regenerated as malate is oxidized back to oxaloacetate, completing the cycle.

What is the importance of the TCA cycle in overall metabolism?

It integrates carbohydrate, lipid, and protein metabolism and is vital for energy production and biosynthesis.

How do ketone bodies relate to the TCA cycle?

Ketone bodies can be converted back to acetyl-CoA, which can enter the TCA cycle for energy production.

What is the effect of high energy charge on the TCA cycle?

High levels of ATP and NADH inhibit the TCA cycle, reducing metabolic flux when energy is plentiful.

What is the purpose of the Pyruvate Dehydrogenase Complex (PDHC)?

To convert pyruvate into acetyl-CoA, linking glycolysis to the TCA cycle.

What are the three enzymes that make up the Pyruvate Dehydrogenase Complex (PDHC)?

E1: Pyruvate Dehydrogenase, E2: Dihydrolipoyl Transacetylase, E3: Dihydrolipoyl Dehydrogenase.

What cofactors are involved in the reactions catalyzed by PDHC?

TPP, lipoic acid, CoA, FAD, and NAD+.

What effect does NADH have on the regulation of PDHC?

NADH inhibits PDHC, signaling a high-energy state.

What activates the Pyruvate Dehydrogenase Complex?

Ca²⁺ and ADP activate PDHC, indicating a need for ATP production.

What is the overall reaction catalyzed by the Pyruvate Dehydrogenase Complex?

Pyruvate + CoA + NAD+ → Acetyl-CoA + CO₂ + NADH.

What is the significance of the thioester bond in acetyl-CoA?

It is a high-energy bond that drives the formation of acetyl-CoA.

How does arsenic poisoning affect the PDHC?

Arsenic inactivates lipoamide, a key cofactor necessary for PDHC function.

What is the result of Vitamin B1 (Thiamine) deficiency?

It results in beriberi, affecting the nervous and cardiovascular systems.

What is the role of lipoic acid in the PDHC?

Lipoic acid aids in the transfer of acetyl groups as part of the enzyme complex.

How does PDHC contribute to ATP production?

By converting pyruvate into acetyl-CoA, it allows entry into the TCA cycle, which drives ATP synthesis.

What is the role of insulin in PDHC regulation?

Insulin activates Pyruvate Dehydrogenase Phosphatase, which dephosphorylates and activates PDHC.

What are some dietary sources of TPP (Vitamin B1)?

Meat, nuts, and whole grains.

How does PDHC function as a regulatory point in metabolism?

It is an irreversible step, regulating the flow from glycolysis into the TCA cycle.

What is an example of an anaplerotic reaction involving pyruvate?

Pyruvate carboxylase converts pyruvate to oxaloacetate, replenishing TCA cycle intermediates.