Why is breast milk not glucose? Lactose, for those who don’t know, is a 2-ringed molecule consisting of a galactose + glucose. There is no net energy gain over glucose, and there’s at least 5 or 6 extra enzymes required to convert both into glucose, which enters glycolysis and generates energy for the body.
Wouldn’t it just have been easier for females to produce glucose instead of wasting energy making the proteins which generate lactose and forcing their offspring to synthesize the proteins which break down lactose? Lactose just doesn’t seem as efficient, but if that were the case it probably would have been outcompeted by females who produced glucose.
I thought it might be one of the following:
-storage
-soluability
-taste: glucose at a similar concentration of lactose may be too sweet
-bacteria: these little guys thrive on glucose, might lactose slow them down?
Any other suggestions as to why lactose is used in breast milk and not glucose?
Why lactose? A cursory search of the web looking for the benefits of lactose yielded only this:
No cites, just that. I hope someone else has more luck.
Since lactose is the sugar of nearly all mammals (except the pinnipeds, platypus and echidna), I expect there is a reason for it. Damned if I can find it tho.
This is pretty shaky speculation, but evolutionarily, it’s helpful in a way. As part of the weaning process, most mammals deactivate the lactase enzyme and become lactose-intolerant. (Lactose tolerant humans are actually the mutants)
So, since lactose is pretty much only found in milk, it mammals are able to able to control how long their offspring can nurse. If they produced glucose, for instance, you couldn’t shut off glucose metabolism without interfering with a lot of other food sources.
I just got home from a 70 hour work week, so I can only hope that this post is somewhat coherent.