Leaf Color Chromatography - Bite Sci-zed

Summary

This script explores the science behind why leaves change color in autumn, focusing on the role of chlorophyll, carotenoids, and anthocyanins in the process. As temperatures drop, chlorophyll production decreases, revealing the yellow and orange hues of carotenoids. Anthocyanins, produced in the fall, add red tones. The script also suggests possible functions of these pigments, like acting as a sunscreen or deterring insects. It concludes with a simple home experiment using isopropyl alcohol and filter paper to demonstrate leaf pigment separation through chromatography, inviting viewers to participate and share their results.

Takeaways

• 🍂 Autumn in Boston is characterized by leaves changing colors on trees.
• 🌿 Leaves derive their color from three main compounds: chlorophyll, carotenoids, and anthocyanins.
• 💚 Chlorophyll, responsible for photosynthesis, gives plants their green color and is present year-round.
• 🥕 Carotenoids, found alongside chlorophyll in chloroplasts, contribute to the yellow and orange hues of leaves.
• 🍇 Anthocyanins are produced in the fall and give leaves their reddish hues, similar to those found in cranberries and blueberries.
• 🔍 As temperatures drop, chlorophyll production decreases, allowing carotenoids' colors to become more visible.
• 🌞 The breakdown of chlorophyll in cooler weather leads to the exposure of other pigments as the green color fades.
• 🌳 The purpose of anthocyanin production in fall is not fully understood, but theories include a sunscreen effect and a deterrent to insects.
• 🧪 A home experiment using isopropyl alcohol and filter paper can visualize the pigments in leaves through a process called paper chromatography.
• 🔍 The experiment involves chopping leaves, soaking them in alcohol, and using filter paper to separate pigments based on their chemical properties.
• 🌈 The result of the chromatography shows distinct bands of pigments, with carotenoids at the top and chlorophyll at the bottom.
• 🌍 The script invites viewers to replicate the experiment and share their findings from leaves around the world.

Q & A

Why do leaves change color in the fall, particularly in Boston?

Leaves change color in the fall due to the breakdown of chlorophyll, which is the green pigment involved in photosynthesis. As temperatures drop, the process of chlorophyll production slows down, allowing other pigments like carotenoids and anthocyanins to become more visible.

What is the role of chlorophyll in plants?

Chlorophyll is crucial for photosynthesis, a process where plants convert carbon dioxide and water into sugar and oxygen using energy from the sun. It gives most plants their green color.

Which compounds are responsible for the yellow and orange hues in leaves?

Carotenoids are the compounds that give leaves their yellow and orange hues. They are present alongside chlorophyll in the chloroplasts throughout the year.

What are anthocyanins and what color do they impart to leaves?

Anthocyanins are compounds that give plants reddish hues. They are produced in the fall when chlorophyll starts to break down, and can also be found in foods like cranberries and blueberries.

Why are anthocyanins produced in the fall?

The exact reason for anthocyanin production in the fall is not definitively known, but theories include acting as a sunscreen for the remaining leaves as the canopy thins, or deterring insects from laying eggs on the tree by appearing unhealthy.

How does the process of photosynthesis occur in chloroplasts?

Photosynthesis occurs in chloroplasts, where chlorophyll and other pigments absorb sunlight and use it to convert carbon dioxide and water into glucose, which is used by the plant for energy, and oxygen, which is released into the atmosphere.

What happens to chlorophyll during the colder months?

During colder months, the production of chlorophyll decreases due to the closure of leaf veins by cool night air, making it harder for water and nutrients to reach the chloroplasts. This results in the breakdown of chlorophyll without being replaced, causing the leaves to lose their green color.

What is the purpose of the experiment described in the script?

The experiment aims to visualize and separate the pigments found in leaves using paper chromatography. This helps to understand the different compounds like chlorophyll, carotenoids, and anthocyanins present in leaves.

What materials are needed for the leaf pigment experiment?

The materials needed for the experiment include isopropyl alcohol, filter paper strips (such as coffee filters), glasses, scissors, and leaves of different kinds.

How does the paper chromatography experiment work?

In paper chromatography, the filter paper acts as the stationary phase, while the isopropyl alcohol is the mobile phase. The alcohol draws up the paper, carrying the leaf pigments with it. Different pigments travel at different rates, separating into distinct bands on the paper strip.

What can one learn from the results of the paper chromatography experiment?

The results of the paper chromatography experiment can show the presence and separation of different pigments in leaves, such as the yellow carotenoids and the green chlorophyll, providing insights into the chemical composition of the leaves.

Outlines

00:00

🍂 Autumn Leaf Color Change

This paragraph explains the science behind why leaves change color in the fall. It begins by discussing the three main compounds responsible for leaf color: chlorophyll, which gives plants their green color and is involved in photosynthesis; carotenoids, which provide yellow and orange hues; and anthocyanins, which produce red shades and are produced in the fall. The paragraph details how the breakdown of chlorophyll during colder weather allows the carotenoids to become more visible and how anthocyanins are produced in response to the breakdown of chlorophyll. It also touches on hypotheses about the purpose of anthocyanins, such as acting as a sunscreen or deterring insects from laying eggs on the tree.

Keywords

💡Chlorophyll

Chlorophyll is a green pigment found in the chloroplasts of plants, which plays a crucial role in photosynthesis by capturing sunlight and converting it into chemical energy. In the video, chlorophyll is mentioned as the compound responsible for the green color of most plants, and its breakdown in the fall leads to the revealing of other pigments, thus changing the leaf colors.

💡Photosynthesis

Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll. The video explains that during photosynthesis, plants convert carbon dioxide and water into glucose and oxygen. This process is central to understanding why chlorophyll is important and how its reduction in fall contributes to the changing of leaf colors.

💡Carotenoids

Carotenoids are a group of pigments that are responsible for the yellow, orange, and red colors in plants and are also found in the chloroplasts alongside chlorophyll. The script mentions carotenoids as the compounds that give leaves their yellow and orange hues, which become more visible when chlorophyll breaks down in the fall.

💡Anthocyanins

Anthocyanins are water-soluble pigments that belong to the flavonoid family, known for giving plants a reddish hue. The video describes anthocyanins as being produced in the fall when chlorophyll breaks down, contributing to the red and purple colors seen in some leaves.

💡Chloroplastic

Chloroplasts are organelles found in plant cells that contain chlorophyll and are the site of photosynthesis. The script refers to chloroplasts as the location where both chlorophyll and carotenoids are present year-round, highlighting their importance in the process of photosynthesis and the display of leaf colors.

💡Leaf Veins

Leaf veins are the vascular tissues that run through leaves, providing water and nutrients to the leaf. The video script explains that as the weather gets colder, the leaf veins close off, making it difficult for water and nutrients to reach the chloroplasts, which affects the production of chlorophyll and leads to the changing of leaf colors.

💡Pigment

Pigments are substances that give color to living tissues. In the context of the video, pigments such as chlorophyll, carotenoids, and anthocyanins are discussed as the key compounds that determine the color of leaves, especially during the fall season when their relative concentrations change.

💡Chromatography

Chromatography is a method used to separate mixtures into their individual components based on their different affinities to a stationary phase and a mobile phase. The script describes a paper chromatography experiment to separate the pigments found in leaves, illustrating the process by which different pigments can be identified and distinguished.

💡Isopropyl Alcohol

Isopropyl alcohol, also known as rubbing alcohol, is used in the script's described experiment as the mobile phase in paper chromatography. It is used to dissolve and carry the pigments from the leaves up the filter paper, aiding in the separation of the pigments.

💡Filter Paper

Filter paper is a type of paper with a network of tiny pores that allows liquids to pass through while retaining solids. In the video script, filter paper is used in the chromatography experiment to separate the pigments from leaves, with the pigments moving up the paper at different rates.

💡Mortar and Pestle

A mortar and pestle is a tool used for grinding and crushing various substances. Although not used in the script's experiment, it is mentioned as the ideal tool for grinding leaves in isopropyl alcohol to release pigments, which is part of the process to understand the leaf color change mechanism.

Highlights

In Boston, leaves change colors in the fall due to changes in chlorophyll, carotenoids, and anthocyanins.

Chlorophyll, involved in photosynthesis, gives plants their green color.

Carotenoids, present year-round, give leaves yellow and orange hues.

Anthocyanins, produced in fall, give plants reddish hues and are found in cranberries and blueberries.

As days get colder, chlorophyll breaks down and carotenoids become more visible.

Anthocyanins are produced in fall before leaves drop off, but their purpose is still debated.

One theory is anthocyanins act as a sunscreen for remaining leaves as the canopy thins.

Another theory suggests anthocyanins may deter insects from laying eggs on the tree by appearing unhealthy.

A home experiment using isopropyl alcohol and filter paper can visualize leaf pigments.

Chopping leaves finely helps release pigments for the experiment.

Isopropyl alcohol dissolves and extracts pigments from the finely chopped leaves.

Grinding leaves in alcohol with a wooden spoon can substitute for a mortar and pestle.

Using a hot water bath can speed up the pigment extraction process.

Straining the leaf pieces from the alcohol makes it easier to observe color changes.

Paper chromatography separates different compounds in the leaves based on polarity.

The alcohol acts as the mobile phase, drawing up the stationary phase of the filter paper.

Different compounds travel at different rates, creating distinct bands of pigments on the paper strip.

The experiment successfully separates carotenoids and chlorophyll, with carotenoids on top.

The experiment is a simple and engaging way to explore leaf pigments at home.

Transcripts

So why does this turn into this in the fall?

I live in Boston, which means that about this time

each year, the leaves on the trees

start to turn their colors.

Leaves get their color from three main compounds.

The first is chlorophyll, which might sound familiar.

Chlorophyll is involved in photosynthesis,

which is the process by which plants

turn CO2 and water into sugar and oxygen

by harnessing the energy from the sun.

Chlorophyll gives most plants their distinctive green color.

The second group of compounds are the carotenoids,

which sounds a little bit like carrot, which makes sense

because carotenoids give leaves there yellow and orange hues.

Carotenoids are present with chlorophyll in organelles

called chloroplasts year round.

And these chloroplasts are just the organelles

where photosynthesis occurs.

Finally, there's a group of compounds

known as anthocyanins.

And anthocyanins give plants reddish hues.

And they're often found in things

like cranberries, and blueberries,

and lots of dark red leaves.

These anthocyanins are actually produced

in the fall when chlorophyll starts to break down,

but I'm getting ahead of myself.

Now, for most of the year, chlorophyll

is so bright green that it blocks out

some of the yellow and orange hues coming

from the carotenoids.

For most of the growing season, chlorophyll

is constantly being broken down and reproduced.

But as it starts to get colder out,

the cool night air closes off the veins of the leaves.

And it gets harder for water and nutrients

to move into the chloroplasts and rebuild chlorophyll.

So what this means is that the chlorophyll

is being broken down, but it's not being reproduced.

So the green color of the leaves starts to disappear.

This means that the yellows and the oranges of the carotenoids

can start to show through.

But that's not all.

Anthocyanins, by contrast, are not present year round

in the leaves.

Instead, they are actively produced in the fall right

before the leaves drop off the trees.

So why would a plant suddenly want

to start producing a red pigment in a leaf that's

about to drop off anyways?

Scientists haven't reached a definitive conclusion yet.

But they do have some pretty good ideas.

One is that the red pigments act as a sort of direct sunscreen

as the canopy starts to drop leaves.

The leaves that remain are exposed to more light.

And those leaves are losing the sunlight-absorbing powers

of their chlorophyll.

Another cool idea is that the red pigment might actually

trick migrating insects into thinking that the tree is

unhealthy and discouraging them from laying

their eggs on those trees.

So all of this leads us to some pretty cool science

that you can do at home to visualize the pigments found

in leaves where you live.

So all you need for this experiment

is isopropyl alcohol, some strips of filter paper--

I used coffee filters--

a couple glasses, scissors, and some leaves.

And if you want to be super cool,

pick a few different kinds of leaves,

so that you can compare the compounds you find within them.

Step one, chop each of your kinds of leaves up into lots

of little tiny pieces.

We really want to release all of these compounds out

of the leaves.

So the smaller and the finer you chop them,

the better this is going to work.

Next, cover the leaves in isopropyl alcohol.

Now, this is just rubbing alcohol,

so it's not very dangerous.

But you do want to make sure you don't get this in your eyes

or drink it.

The next step is to grind up these leaves in the alcohol.

Now, ideally, you would be doing this with a mortar and pestle.

but I don't have that.

And so I am using a wooden spoon.

Now, at this point, you should start

to see the alcohol change colors as those pigments are released

from the leaves.

If you want to speed this reaction up a bit,

you can set all of your glasses into a hot water bath

and leave them for about 30 minutes.

After this, you can really see the color change

in the alcohol.

Now, I strained the leaves out of my alcohol,

so that it was a little easier to see.

But you could probably leave them in there as well.

Next, cut your filter paper into strips

and place a strip into each glass so that one side of it

is touching the alcohol and the other side is out in the air.

Now, I repeated this experiment later

with longer strips of filter paper

and hung one side out of the edge.

And this actually worked a little bit better.

Now, you want to let your glasses sit for about an hour.

So what we're doing here is called chromatography,

which just means that we are separating a mixture.

Here, we are using paper chromatography

to separate the different compounds within the leaves.

So the alcohol, our mobile phase,

is being drawn up the paper strip, our stationary phase,

and it's pulling leaf pigments along with it.

Depending on their chemical structure,

molecules will have different polarities

and will want to interact with that paper differently.

Some will want to stick tightly onto the paper,

while others will move more easily with the liquid.

This means that some compounds will travel along the paper

faster than others, separating the compounds along the strip,

and giving you distinct bands of compounds.

Cool.

So we actually got some really good separation

between the yellow carotenoids on top

and the green chlorophyll on the bottom.

And the longer you leave these, the better that separation

will get.

Now, this is an experiment you can easily do at home,

and you should.

I want to see what the compounds from leaves from all

around the world look like.

So make a video response of you doing this experiment,

and leave it below.

And I'll check them all out.

And yeah, go on.

Go forth.

Do science.