Bioenergetics & Cellular Respiration: Key Concepts and Pathways

What does the First Law of Thermodynamics state?

Energy cannot be created or destroyed, only transformed.

What is the Second Law of Thermodynamics?

Energy transformations increase entropy and are never 100% efficient.

What is the difference between kinetic and potential energy?

Kinetic energy is the energy of motion, while potential energy is stored energy.

What type of reaction is characterized by ΔG < 0?

Exergonic reactions, which release energy and are spontaneous.

What type of reaction requires energy input and is characterized by ΔG > 0?

Endergonic reactions.

What is the role of enzymes in biochemical reactions?

Enzymes lower activation energy and speed up spontaneous reactions without changing ΔG.

What is oxidation in terms of electron transfer?

Oxidation is the loss of electrons or hydrogen.

What is reduction in terms of electron transfer?

Reduction is the gain of electrons or hydrogen.

What are the outputs of glycolysis per glucose molecule?

2 Pyruvate, 4 ATP (net 2), and 2 NADH.

What are the inputs for the Citric Acid Cycle?

Acetyl-CoA, NAD⁺, and FAD.

What is the total ATP yield from one glucose molecule during aerobic cellular respiration?

Approximately 30-36 ATP.

What is the purpose of fermentation in cells?

To regenerate NAD⁺ so glycolysis can continue without oxygen.

What are the inputs and outputs of lactic acid fermentation?

Inputs: Pyruvate and NADH; Outputs: Lactate and NAD⁺.

What are the inputs and outputs of alcohol fermentation?

Inputs: Pyruvate; Outputs: CO₂, acetaldehyde, ethanol, and NAD⁺.

How do carbohydrates, fats, and proteins enter cellular respiration?

They feed into glycolysis or the Citric Acid Cycle at different points.

What is the final electron acceptor in aerobic respiration?

Oxygen (O₂).

What are NADH and FADH₂ in cellular respiration?

They are high-energy electron carriers that donate electrons to the electron transport chain.

What is the energy hierarchy of ATP, ADP, and inorganic phosphate (Pi)?

ATP > ADP > Pi.

What happens during pyruvate oxidation?

Pyruvate is converted to Acetyl-CoA, producing CO₂ and NADH.

What are the outputs of the Citric Acid Cycle per glucose molecule?

4 CO₂, 6 NADH, 2 FADH₂, and 2 ATP.

What is reaction coupling in metabolic processes?

Pairing exergonic reactions (like ATP hydrolysis) with endergonic reactions (like biosynthesis).