Bioenergetics and Cellular Respiration

What are the two types of metabolic pathways?,

Catabolic (breakdown, exergonic) and Anabolic (biosynthesis, endergonic).

What is an amphibolic pathway?

,A pathway that can function in both catabolism and anabolism depending on cellular conditions.

What are the five principles of metabolism?,

1. Metabolic pathways are irreversible,

2. Catabolic and anabolic pathways must differ,

3. Every pathway has a committed step,

4. Pathways are regulated,

5. Pathways occur in specific cellular locations.

What is the first law of thermodynamics?

,Energy can be transformed, but it cannot be created or destroyed.

What is the second law of thermodynamics?,

Energy transformations increase entropy, and only free energy can be used to do work.

What is Gibbs Free Energy (ΔG)?,

It represents the usable energy in a reaction that can do work.

What does a negative ΔG indicate?,

An exergonic reaction that occurs spontaneously, releasing energy.

What does a positive ΔG indicate?

,An endergonic reaction that requires energy input to proceed.

How are exergonic and endergonic reactions coupled?

,Energy released from an exergonic reaction is used to drive an endergonic reaction.

What are high-energy compounds?,

Molecules with highly negative ΔG values upon hydrolysis, such as ATP.

What are the two main ways ATP is generated?,

Substrate-level phosphorylation and oxidative phosphorylation.

What is the main function of the TCA cycle?,

To oxidize Acetyl-CoA to CO2 and generate NADH and FADH2 for ATP production.

What are the sources of Acetyl-CoA?,

Metabolism of carbohydrates, lipids, and proteins.

What is the net ATP yield from one molecule of glucose?

,Approx. 30-32 ATP molecules.

What are the key regulatory enzymes of the TCA cycle?,

Citrate synthase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase complex.

What are anaplerotic reactions?,

Reactions that replenish TCA cycle intermediates.

What is the electron transport chain (ETC)?

,A series of protein complexes in the mitochondria that transfer electrons and create a proton gradient.

Where does the electron transport chain occur?

,In the inner mitochondrial membrane.

What are the main electron donors to the ETC?,

NADH and FADH2.

What is the final electron acceptor in the ETC?

,Oxygen (O2), which forms water.

What are the four complexes of the ETC?

,Complex I (NADH dehydrogenase), Complex II (Succinate dehydrogenase), Complex III (Cytochrome bc1 complex), Complex IV (Cytochrome c oxidase).

Which complex does FADH2 enter the ETC through?

,Complex II (Succinate dehydrogenase).

What is the proton gradient used for?,

Driving ATP synthesis through ATP synthase (Complex V).

What is chemiosmosis?,

The movement of protons across the mitochondrial membrane to drive ATP synthesis.

What is oxidative phosphorylation?,

ATP generation using the proton gradient created by the ETC.

What is the P/O ratio for NADH and FADH2?

,NADH: 2.5 ATP, FADH2: 1.5 ATP.

What is the glycerophosphate shuttle?,

A mechanism in the brain and muscle that transfers electrons from NADH to FADH2 for entry into the ETC.

What is the malate-aspartate shuttle?,

A mechanism in the liver, heart, and kidneys that allows cytoplasmic NADH to enter the mitochondria for ATP production.

What are ETC inhibitors?,

Compounds that block electron transfer, such as rotenone, cyanide, and antimycin A.

What is an uncoupling agent?

,A molecule like DNP that disrupts the proton gradient, leading to heat production instead of ATP synthesis.

What is the role of thermogenin (UCP1)?

,An uncoupling protein in brown fat that generates heat instead of ATP.

How does cyanide inhibit the ETC?,

It binds to Complex IV, preventing oxygen reduction and halting ATP production.

What is the role of ATP synthase?,

It synthesizes ATP using the proton gradient generated by the ETC.

How does ATP synthase work?,

Protons flow through the F0 subunit, causing rotation that drives ATP synthesis in the F1 subunit.

What regulates oxidative phosphorylation?,

The availability of ADP, oxygen, and the NADH/NAD+ ratio.

How does hypoxia affect metabolism?,

It increases glycolysis and lactate production while reducing aerobic ATP synthesis.

What is the Warburg effect?,

Cancer cells favor anaerobic glycolysis even in the presence of oxygen.

How does citrate regulate glycolysis?

,Citrate inhibits phosphofructokinase-1 (PFK-1), reducing glycolysis when ATP is abundant.

How does fatty acid oxidation regulate glycolysis?,

Fatty acid oxidation produces Acetyl-CoA, which inhibits glycolysis by reducing pyruvate dehydrogenase activity.

What is the role of Vitamin B3 (Niacin) in metabolism?,

It is a precursor for NAD+ and NADP+, which are essential for redox reactions.

What is the function of Vitamin B1 (Thiamine)?,

It is a coenzyme in decarboxylation reactions such as pyruvate dehydrogenase and α-ketoglutarate dehydrogenase.

Why is Vitamin B2 (Riboflavin) important?,

It is a precursor for FAD and FMN, essential in the electron transport chain.

What is the function of Vitamin B5 (Pantothenic acid)?,

It is a component of Coenzyme A, crucial for Acetyl-CoA formation and metabolism.

How does the deficiency of Pyruvate Dehydrogenase affect metabolism?,

It impairs aerobic metabolism, leading to lactic acidosis and neurological defects.