A biochemical pathway for a cellular behaviour: pHi, phosphorylcreatine shuttles, and sperm motility

Sperm motility and respiration are tightly coupled processes, both activated by an increased intracellular pH (pHi). As the sperm pHi increases, the flagellar motor driving motility is activated, leading to ATP consumption. Energy for motility is provided by mitochondrial respiration; energy transport from sperm mitochondrion to tail involves distinct isozymes of creatine kinase that effect a phosphorylcreatine shuttle. The activation of sperm motility and respiration can be described as a linked series of biochemical reactions that form a cell behavioural pathway analogous to the reaction sequences of intermediary metabolism.