Electron transport, chemiosmosis and oxidative phosphorylation

What the exam asks

In Section I multiple-choice sets and Section II free-response questions (especially Q1 Interpreting and Evaluating Experimental Results, Q4 Conceptual Analysis and Q5 Analyze Model or Visual Representation), you must:

• Trace the path of electrons from $\text{NADH}$ and $\text{FADH}_2$ to $\text{O}_2$ and link electron flow to active proton ($\text{H}^+$) transport.
• Relate proton concentration ($[\text{H}^+]$) to pH across membranes.
• Predict the precise effects of electron transport chain (ETC) inhibitors, ATP synthase blockers and protonophores (uncouplers).
• Compare chemiosmosis across mitochondria, chloroplasts and prokaryotes.

Core ideas

The electron transport chain and proton gradient

During glycolysis and the Krebs cycle, $\text{NAD}^+$ and $\text{FAD}$ are reduced to $\text{NADH}$ and $\text{FADH}_2$. These electron carriers deliver high-energy electrons to the electron transport chain embedded in the (folded into , which increase the surface area-to-volume ratio to hold more ETC proteins and ATP synthase complexes).

1. Oxidation of carriers: $\text{NADH}$ and $\text{FADH}_2$ are oxidized back to $\text{NAD}^+$ and $\text{FAD}$ (which are recycled to keep glycolysis and the Krebs cycle running).