Photosynthetic growth despite a broken Q-cycle

Photosynthetic growth despite a broken Q-cycle

Central in respiration or photosynthesis, the cytochrome bc(1) and b(6)f complexes are regarded as functionally similar quinol oxidoreductases. They both catalyse a redox loop, the Q-cycle, which couples electron and proton transfer. This loop involves a bifurcated electron transfer step considered as being mechanistically mandatory, making the Q-cycle indispensable for growth. Attempts to fals...

A note on a broken-cycle theorem for hypergraphs

Whitney’s Broken-cycle Theorem states the chromatic polynomial of a graph as a sum over special edge subsets. We give a definition of cycles in hypergraphs that preserves the statement of the theorem there.

Fixing the Q cycle.

Mitchell's key insight that all bioenergetic membranes run on the conversion of redox energy into transmembrane electrical and proton gradients took the form 30 years ago of a working model of the Q cycle of cytochrome bc1, which operates reversibly on coupled electron and proton transfers of quinone at two binding sites on opposite membrane faces. His remarkable model still stands today, but h...

A Broken Metallic Tracheostomy Tube

A Growth Cycle

Presented here is a starkly schematized and hence quite unrealistic model of cycles in growth rates. This type of formulation now seems to me to have better prospects than the more usual treatment of growth theory or of cycle theory, separately or in combination. Many of the bits of reasoning are common to both, but in the present paper they are put together in a different way. The following as...