Topics / Biochemistry
Energy, Electrons, and Networks
Biochemistry, read abstractly, is the study of how living things capture energy, move electrons, and route matter through networks of reactions. This route stays at that level: the patterns that repeat from a kitchen culture to a bacterium to a leaf, before the names of individual molecules.
Five Patterns That Repeat
An energy currency
Cells do not spend energy directly from food or light. They convert it into a common currency, mostly ATP, and spend that wherever work is needed.
wiki: ATPElectrons flowing downhill
Redox chemistry moves electrons from a donor to an acceptor. An electron transport chain lets that fall happen in small steps, and the steps pump the gradient that makes ATP.
wiki: electron transportCatalysts that choose
Enzymes speed particular reactions by many orders of magnitude and ignore others. Which enzymes a cell makes is, in effect, which chemistry it allows.
wiki: enzyme kineticsPathways as networks
Metabolism is a graph: molecules are nodes, reactions are edges, and a cell routes flow through it as conditions change. The same network can run in different directions.
wiki: metabolic networkHarvesting light
Photosynthetic organisms catch light with pigments and use it to drive electrons uphill. Not all of them split water or release oxygen; some bacteria photosynthesize using other electron donors entirely.
wiki: photosynthesisParallel and Competing Theories
Biochemistry was practiced long before it was named, and some of its most consequential results came from China.
Qu, the first koji
Chinese brewers cultivated qu, a starter of molds such as Aspergillus, for millennia to turn grain starch into sugar and alcohol; Japanese koji descends from it. Enzymes, domesticated before anyone could see them.
wiki: Aspergillus oryzaeTu Youyou and artemisinin
Reading a fourth-century remedy by Ge Hong, Tu Youyou extracted artemisinin at low temperature and gave the world a leading malaria treatment; she shared the 2015 Nobel Prize.
wiki: Tu Youyou