Why does your fridge start to smell,
and where does that icky black liquid come from?
Wouldn't life just be easier if things didn't rot,
if things lasted forever?
Well, maybe, but probably not.
The average American household wastes about 25% of its food,
and a lot of restaurants are even worse.
So if we didn't have decomposition,
what would happen to all the food we throw away?
Food in landfills usually gets dealt with by bacteria,
protease, and fungi, who allow nutrients in the food
to return to the soil and eventually other living things.
These decompositions also break down
other dead stuff like trees.
In fact, they're pretty much the only thing that can eat wood.
So even if in a world without rot,
you don't have to worry about your house getting
eaten by termites who rely on protease in their stomachs.
Pretty soon forests and landfills
will be flooded with a lot of dead stuff.
How do we avoid this problem?
Well, basically in your fridge, on a forest floor,
in a dumpster, almost anywhere, there
are fungi, bacteria, and protease that
live entirely by eating stuff.
These dead things can be more or less divided
into three categories-- carbohydrates, sugar
and starches; lipids, think fats; and proteins like meat.
All of these are chemically different,
so they each get broken down by different enzymes
in different ways before being absorbed by decomposers.
For example, proteases break down proteins
into amino acids, the cell's building blocks.
Lipids rely on lipases and carbohydrates
on things like amylase and cellulases.
So how does a perfectly nice broccoli floret
start giving off this foul black liquid?
Fruits and vegetables are almost entirely made of water.
So on the most basic level, you could
say the cells are like extremely complex water balloons.
The exterior, or cell wall, is made
of cellulose, a complex carbohydrate that
gets broken down by enzymes into small sugars the cell can
get energy from.
The bacteria or fungi uses cellulase to eat
the exterior of a cell, it's like
if I were to pop the balloon.
That's the muck you see in your fridge.
What about that stink?
For fruits and vegetables, a lot of time the smell
happens after the icky black liquid forms.
Other bacteria that weren't involved
in the initial colonization move in
and start to stink everything up.
Meat get's smelly when lipases break down fat in the meat
into glycerol and fatty acids to energy sources,
and fatty acids are kind of gross.
And so while food rotting may smell absolutely terrible,
because of it, the environment is able to recycle
crucial nutrients it needs.
And, well, that's why we have all this.
[MUSIC PLAYING]