What are photosynthetic pigments?

Photosynthetic pigments are compounds that absorb light energy and act as electron donors during photosynthesis.

Why do plants have more than one photosynthetic pigment?

Having multiple pigments allows plants to absorb a wider range of light wavelengths, enhancing photosynthesis.

What is the absorption spectrum?

The absorption spectrum is a graph showing how much light is absorbed by each pigment at different wavelengths.

What is the action spectrum?

The action spectrum indicates how much light is used for physiological processes like photosynthesis.

Why do seaweeds appear red or brown?

Seaweeds often appear red or brown because their pigments do not absorb red wavelengths of light, which are absorbed by water first.

How does water depth affect photosynthesis in seaweed?

As water depth increases, less light reaches seaweed, so they adapt by having pigments that absorb available wavelengths.

What wavelengths of light are absorbed by water?

Water absorbs light starting with red wavelengths, making them unavailable for photosynthesis at greater depths.

How do tides affect seaweed photosynthesis?

Tides change the water depth above seaweed, so they possess various pigments to maintain photosynthesis under different conditions.

Photosynthetic Pigments

00:06:13

https://www.youtube.com/watch?v=HTWUS_yb1Bw

Summary

TLDRThe video discusses photosynthetic pigments, focusing on their importance beyond chlorophyll. It explains how these pigments absorb light energy, with chlorophyll reflecting green light, which is why plants appear green. The absorption and action spectra are introduced, showing the relationship between light absorption and photosynthesis rates. The video highlights seaweed's adaptation to underwater light conditions, explaining that they possess pigments that absorb only the wavelengths of light that reach them, particularly in varying water depths. This adaptation ensures efficient photosynthesis despite changing light availability.

Takeaways

🌱 Photosynthetic pigments are crucial for light absorption.
🌈 Chlorophyll reflects green light, making plants appear green.
📊 Absorption spectra show how pigments absorb different light wavelengths.
🔬 Action spectra correlate light absorption with photosynthesis rates.
🌊 Seaweed adapts to underwater light conditions with specific pigments.
🔴 Red light is absorbed first by water, affecting seaweed color.
📏 Water depth influences the availability of light for photosynthesis.
🌿 More pigments mean more light absorption and glucose production.
🌊 Tides change water depth, requiring seaweed to adapt their pigments.

Timeline

00:00:00 - 00:06:13
The video introduces photosynthetic pigments, focusing on chlorophyll and other pigments. It outlines learning objectives, including understanding the advantages of multiple pigments and how their ratios change with depth in seaweed. Photosynthetic pigments act as electron donors, becoming excited by light energy and releasing electrons. The absorption spectra graph illustrates how different pigments absorb light at various wavelengths, highlighting that green light is reflected, not absorbed, making plants appear green. The action spectra graph correlates light absorption with photosynthesis rates, showing that more pigments allow for greater light absorption and increased glucose production. Seaweed, living underwater, has adapted pigments to absorb available light wavelengths, as water absorbs light at different depths. Red light is absorbed first, leading to the prevalence of red and brown pigments in seaweed. The video concludes by emphasizing the importance of diverse pigments for maximizing photosynthesis and adapting to changing water depths.

Mind Map

Video Q&A

What are photosynthetic pigments?
Photosynthetic pigments are compounds that absorb light energy and act as electron donors during photosynthesis.
Why do plants have more than one photosynthetic pigment?
Having multiple pigments allows plants to absorb a wider range of light wavelengths, enhancing photosynthesis.
What is the absorption spectrum?
The absorption spectrum is a graph showing how much light is absorbed by each pigment at different wavelengths.
What is the action spectrum?
The action spectrum indicates how much light is used for physiological processes like photosynthesis.
Why do seaweeds appear red or brown?
Seaweeds often appear red or brown because their pigments do not absorb red wavelengths of light, which are absorbed by water first.
How does water depth affect photosynthesis in seaweed?
As water depth increases, less light reaches seaweed, so they adapt by having pigments that absorb available wavelengths.
What wavelengths of light are absorbed by water?
Water absorbs light starting with red wavelengths, making them unavailable for photosynthesis at greater depths.
How do tides affect seaweed photosynthesis?
Tides change the water depth above seaweed, so they possess various pigments to maintain photosynthesis under different conditions.

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Subtitles

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00:00:01
in this video we're going to be looking
00:00:02
at photosynthetic pigments and most
00:00:05
people have already heard of one
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photosynthetic pigment and that's
00:00:09
chlorophyll but today in this video
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we're going to look a little bit beyond
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chlorophyll so let's have a little look
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at our learning objectives you're going
00:00:18
to understand why it's advantageous to
00:00:20
have more than one photosynthetic
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pigment and you're going to suggest why
00:00:24
the ratio of photosynthetic pigments of
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seaweed changes with depth let's let's
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get
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started the first question to ask is
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what is a photosynthetic
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pigment well it acts as an electron
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donor and the reason for this will
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become clear in a different video when
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we look at the light dependent reaction
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of
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photosynthesis but for now a
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photosynthetic pigment is a compound
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which is easily excited by light energy
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and when those compounds become excited
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they release electrons they lose
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electrons
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so we're going to have a look at
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something called the absorption spectra
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and what this is is a diagram or a graph
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that shows how much light is absorbed by
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each
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pigment they're plotted with wavelength
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which determines the color of the light
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on the xais so here's an example of an
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absorption
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spectra we can see we've got three
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different photop pigments there we've
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got chlorophyll a we've got Chlorophyll
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B B and we've got carotenoids and on the
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xaxis we've got wavelength of light in
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nanometers ranging from ultraviolet on
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the left to infrared on the far
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right what we notice is in the middle
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around the green and yellow wavelengths
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of light we see a region where barely
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any light is being absorbed and in fact
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it's most of the green light that isn't
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absorbed and that's because the green
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light is being reflected by the uh the
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Chlor the chlorophyll and the other
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photop pigments which is what makes
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plants appear
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green most students think that the
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reason a plant appears green is because
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green is the wavelength of light that
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the plants use it's not true it's one of
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the only wavelengths of light that the
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plants don't use that's what's being
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reflected back to our eyes every other
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color of light every other wavelength of
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light has been absorbed and utilized by
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the plant green light is not used it's
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being reflected back to our
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eyes the second type of graph you have
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to be able to uh to interpret is the
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action Spectra and an action Spectra
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shows how much of the light is used for
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physiological processes and this in this
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case we're talking
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photosynthesis once again we've got the
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wavelength of light on the x-axis so
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that's the color so here's an example of
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an action
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Spectra and here we see that on the left
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and the right of the graph where we had
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a lot of absorption a lot of light being
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absorbed by by the pigments we get a lot
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of photosynthesis happening and we
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notice that in the Middle where we
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didn't have much light being absorbed we
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have relatively little photosynthesis
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occurring and this means that the amount
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of light being absorbed by those
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photosynthetic pigments is directly
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correlating with the rate of
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photosynthesis that's happening in the
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plant so why do we bother or why do
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plants bother having more than one
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photosynthetic pigment well the more
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pigments you have the more different
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wavelengths of light can be
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absorbed and by absorbing more light
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well that means we can do more
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photosynthesis generate more
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glucose which means the plants can grow
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more so we're going to look at a
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specific
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example of pigments in photosynthesis
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and this is in
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seaweed now seaweed lives underwater OB
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obviously um and water absorbs
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light in fact the deeper we go the less
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wavelengths of light are available to be
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absorbed by the plant so the deeper we
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go the more and more light is being
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absorbed by the water so here's a little
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diagram to illustrate this then we
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notice that the first wavelength of
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light to be absorbed is at the red end
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of the spectrum so close to the surface
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in fact between 0o and about 3 m we're
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losing red light the red wavelengths of
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light entirely
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and we progress through so that as we go
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further and further down we lose more
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and more wavelengths of
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light what we notice is that in seaweed
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because red light is the first
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wavelength of light to be absorbed by
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the water most seaweeds are often red or
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brown because their photosynthetic
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pigments do not absorb the red
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wavelengths of light
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if a wavelength of light will never
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reach you there's no point in having a
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pigment to absorb it it's a waste of
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resources now the amount of water above
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a plant isn't always constant with Tides
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the amount of water above seaweed will
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change so seaweeds always have a
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selection of useful photo pigments so
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that when the change in the water depth
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changes it's not going to affect their
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ability to
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photosynthesize so here's a little bit
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of further reading scan this with your
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smartphone or your IAD and it's a
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selection of notes on photosynthesis
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from A2 biology 101 which is a really
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really good revision
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blog so to summarize plants contain many
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different photosynthetic
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pigments and what this allows them to do
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is to absorb as much light as possible
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for photosynthesis
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and seaweeds only have photo pigments
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that will absorb wavelengths of light
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that will reach them because some of
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it's absorbed by the
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water and that's it thank you