NATHAN: 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.
According to the USDA, the average American household
wastes 25% of its food, and a lot of restaurants
are even worse.
So if we didn't have decomposition,
what would happen to the food we throw away?
Food in landfills normally gets dealt with by bacteria, fungi,
and protists that allow the nutrients in food to return
to the soil, and eventually, other living things.
These decomposers also break down other dead stuff,
like trees.
In fact, they're pretty much the only thing that can eat wood.
So in a world without rot, while your home may not
have to worry about being eaten by termites
who rely on protists in their stomach,
pretty soon, forests and landfills
would 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 protists that live entirely
by eating dead stuff.
These dead things can be more or less divided
into three categories.
Carbohydrates-- sugar and starches.
Lipids-- think fats.
And proteins, like meats.
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 that 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.
When a bacteria or fungi or 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.
That's how you get that icky black liquid.
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 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 your food rotting may smells absolutely terrible,
because of it, the environment is able to recycle
crucial nutrients it needs.
And, well, that's why we have all this.