The simple story of photosynthesis and food - Amanda Ooten

Transcriber: Andrea McDonough Reviewer: Bedirhan Cinar

Ever wonder where most of the food

you eat every day comes from?

Well, about 60% of the food you eat

is carbohydrates.

As you can probably tell from its name,

carbohydrates contain carbon,

hydrogen,

and oxygen.

But where do these atoms originally come from

and how do they join together

to make delicious foods like fruits and pasta?

It actually all starts with the air

you are exhaling this very minute,

specifically the carbon dioxide molecules.

Plants are going to breath in

this very same carbon dioxide

through pores in their skin, called stomata.

Plants drink in water from their roots

to get the needed oxygen and hydrogen atoms,

and their electrons,

in order to build carbohydrates.

What is that thing?

Well, that's a special plant organelle

inside the leaves of plants

called a chloroplast.

It's green beceause of a special light-absorbing pigment

called chlorophyll.

Each leaf has about 44,000 cells

and every cell can have anywhere

between 20 to 100 chloroplasts.

That's up to 4,400,000 chloroplasts!

By now, you've probably guessed

that we're talking about the process of photosynthesis

and you might be wondering

when the sun is going to make its entrance.

Let's go back to that original molecule of water.

The plant has to split this molecule of water

so it can get electrons from it.

But, the plant can't pull that water apart by itself.

It needs help from the high-energy rays of the sun.

So now that the chloroplast has all the building blocks

- carbon, hydrogen, oxygen, and electrons -

it can use them to go through

the rest of the steps of photosynthesis

to transform that original carbon dioxide gas

into a simple carbohydrate called glucose,

C-6-H-12-O-6.

That little glucose molecule then helps to build

bigger and better carbohydrates

like cellulose.

Cellulose is a type of carbohydrate found in plants

that our body cannot break down.

We call it fiber

and we eat it in vegetables like lettuce,

broccoli,

and celery.

Plants use cellulose to keep themselves strong.

The plant could also turn that glucose into starch,

a large molecule that stores energy for the plant.

We love eating starch from plants like potatoes,

corn,

and rice.

So you see, when you eat plants,

we're actually benefiting from photosynthesis.

The plant makes things like starch,

which we eat

and then break back down into glucose,

the first form the plant made.

Then, the mitochondria in our cells,

powered by the oxygen we breath,

can turn glucose into pure energy molecules

called ATP.

ATP powers all work done

by each and every one of your cells,

things like communication,

movement,

and transport.

But why do we have to turn that glucose into ATP?

Well, think of it like this.

You're excited to start your summer job

at the local ice cream stand,

but your boss has just told you

that she is going to pay you in ice cream cones.

What are you going to be able to do

with those ice cream cones?

Nothing,

which is why you kindly asked to be paid in dollars.

ATP is just like dollars.

It is the currency that all cells of life use

while glucose is,

well, kind of like ice cream.

Even plants have mitochondria in their cells

to break down the glucose they make into ATP.

So as you can see,

humans and plants are intricately connected.

The air we breath out

is used by plants to make the carbohydrates

we enjoy so much.

And, in the process,

they are releasing the very same oxygen molecules

we need to breath in

in order that our mitochondria can break down

our delicous carbohydrate meal.