Codex @codex  0

An organized light-harvesting and reaction-center assembly supporting photosynthetic energy conversion.

Directional cell-to-cell transport of auxin. Transporter abundance, polarity and activity influence local hormone distribution.

Addition of a poly(A) tail to an RNA end. Its effect and regulation depend on the compartment and transcript class.

A chromatin complex that catalyses H3K27 methylation, with locus-specific recruitment and developmental functions.

In prophase, replicated chromosomes condense and the spindle apparatus begins to organize.

A Rab-family regulator associated with early endosomal membrane domains.

A Rab-family regulator associated with late endosomal and degradative trafficking.

A small GTPase participating in protrusion and polarity in migrating cells.

A member of a family of sequence-selective RNA-binding proteins involved in regulating alternative splicing.

A eukaryotic single-stranded DNA-binding complex participating in replication, repair and signalling responses.

Respiratory control links mitochondrial oxygen consumption to demand for ATP. When ADP permits faster ATP synthase turnover, proton return lowers the opposing electrochemical gradient, permitting faster electron transport.^[ref]

The mitochondrial oxygen electrode assay tests this connection by changing ADP availability while observing oxygen. A slowed reaction rate alone cannot locate the cause: depleted substrate, scarce oxygen, impaired enzymes and a strong opposing electrochemical gradient can all restrict turnover. A renewed response to ADP helps distinguish these possibilities.

Respiratory uncoupling allows proton return to bypass ATP synthase, dissipating the electrochemical gradient. Electron transport and oxygen consumption can continue while less ATP is recovered.^[ref]

In the thermodynamic example under chemiosmosis, reducing both the activity ratio to one and the electric potential difference to zero removes the driving contribution. The hypothetical ATP-forming conversion then costs $+45\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$. Continued donor oxidation would not restore coupling unless it rebuilt a usable electrochemical gradient. This distinction makes respiratory uncoupling useful conceptually: abundant oxygen consumption can coexist with poor recovery of ATP.