Oxidative Decarboxylation and Citric Acid Cycle

This stage occurs in the mitochondrial matrix, where pyruvate is converted to acetyl-CoA and enters the citric acid cycle. The process generates NADH and FADH₂ as electron carriers.

Definition: Oxidative decarboxylation is the process of removing a carboxyl group as CO₂ while simultaneously oxidizing the molecule.

Highlight: The citric acid cycle is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA.

Example: The conversion of pyruvate to acetyl-CoA involves the removal of one carbon atom as CO₂ and the generation of NADH.

Electron Transport Chain and ATP Synthesis

The electron transport chain, located in the inner mitochondrial membrane, is the final stage of cellular respiration. It uses the electron carriers produced in previous stages to generate ATP through chemiosmosis.

Definition: The electron transport chain is a series of proteins that transfer electrons from electron donors to electron acceptors via redox reactions coupled with proton transfer.

Highlight: The proton gradient created drives ATP synthesis through ATP synthase.

Example: For each NADH molecule, 10 protons are transported across the membrane, generating 3 ATP molecules.

Energy Coupling and Cellular Organization

The process demonstrates how energy-releasing reactions are coupled with energy-requiring reactions to drive cellular processes. The spatial organization of mitochondria is crucial for efficient energy production.

Definition: Energy coupling is the use of energy released from one reaction to drive another reaction that requires energy.

Vocabulary: Cristae - the folded inner membrane of mitochondria where the electron transport chain is located.

Transport Mechanisms

Various transport mechanisms facilitate the movement of molecules across cellular membranes, essential for cellular respiration.

Definition: Active transport moves molecules against their concentration gradient using energy from ATP.

Example: The ATP-dependent sodium-potassium pump is an example of active transport.

Highlight: Transport proteins can be classified as uniporters, symporters, or antiporters based on their mechanism of action.

Glycolysis Overview

The first stage of cellular respiration occurs in the cytoplasm, where glucose undergoes a series of enzymatic reactions to produce pyruvate. This process generates a net gain of 2 ATP molecules and 2 NADH.

Definition: Glycolysis is the metabolic pathway that converts glucose into pyruvate through a series of 10 enzyme-catalyzed reactions.

Highlight: The process can be divided into two phases: an energy investment phase $-2 ATP$ and an energy yielding phase $+4 ATP$.

Example: The conversion of glucose to glucose-6-phosphate requires ATP investment, while the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate generates ATP.

Vocabulary: Substrate-level phosphorylation - the direct transfer of a phosphate group from a phosphorylated compound to ADP to form ATP.