Biology
/
Photosynthetic Pigments

Photosynthetic Pigments

Shiken premium Upgrade Banner

Photosynthesis is a complex process, and biologists use various methods to understand it better. One of these methods is called chromat, which analyses the different photosynthetic pigments found in leaves. These pigments are tiny molecules that absorb light energy. The most common pigment found in leaves is chlorophyll, which gives plants their green color. Chlorophyll absorbs blue and red light and reflects green light, which is why plants look green. Chloroplasts are also essential for photosynthesis, as they contain chlorophyll and help convert light energy into chemical energy. Without them, plants wouldn't be able to absorb light energy, and photosynthesis couldn't happen. If you want to learn more about this fascinating process check out our on.

What is chromatography?

Chromatography is a technique used in laboratories by biologists and biochemists to separate mixtures. It works by passing the mixture in a solution or suspension where each component moves at rates. This method is used fromreacted solution. There are two primary types of chromatography: thin-layer chromatography (TLC) and column chromatography. Both methods serve the same function, but they use different equipment to separate the mixture into its various components. If you are a student, you are most likely to use thin-layer chromatography. However, at the university level or in a professional laboratory, both methods are used. The differences between the two are illustrated in Figure 1 below.

How do you investigate photosynthesis using chromatography?

As part of your A-level course, you will be required to use chromatography to investigate the pigments extracted from the leaves of different plants. You may be asked to compare the pigments of leaves from shade-tolerant versus shade-intolerant plants or leaves that are different colors from the same plant. To do this, follow the steps below.

First, use a pencil to draw a straight line about 1 cm above the bottom of the filter paper. It is essential to use a pencil instead of a pen, as pen ink can affect your results. Next, take a section of the leaf and place it into a mortar. Add 20 drops of acetone and grind the leaves with the acetone using a pestle. This will release the pigments in the leaf. Using a capillary tube, extract the pigment and drop it onto the centre of the pencil line on the filter paper. Be sure to suspend the filter paper with the pigment in the solvent, but don't let the liquid level go above the. solvent close top doesn through the paper. Finally, remove the paper from the solvent and draw a pencil line marking where the solvent has moved up. You should notice that the pigment has separated into different compounds, which should all be placed at different heights above the first pencil line.

 

Example of Thin Layer Chromatography
Example of Thin Layer Chromatography

Although this won't look exactly like your experiment, it will be set up similarly.

How do you calculate an Rf value?

After collecting your filter paper with the separated pigments, you will need to calculate the Rf value of each spot. The Rf value is the retention factor, and it is used to identify the pigments present in your chromatography sample.

The equation for the Rf value is as follows:

When calculating the Rf value for each spot, it is essential to measure to the center of each spot, not the edge.

Once you have your set of Rf values, compare them to the known Rf values provided by your teacher to identify the pigments present in your leaf. If you need to find your own database, make sure it is specifically for paper chromatography and that you use the same solvent as used in your experiment, since these variables will affect the distance travelled by certain pigments!

Which photosynthetic pigments are in chloroplasts?

You are likely to find the following pigments in a leaf during chromatography:

Chlorophyll c is another important photosynthetic pigment; however, you will not find it in your chromatography experiment. This is because it is not found in plants but in microorganisms capable of performing photosynthesis!

Why are photosynthetic pigments important in photosynthesis?

Photosynthetic pigments are crucial to photosynthesis as they absorb photons  (waves of light) at certain wavelengths. As you will see in the diagram below, different pigments can absorb and reflect different wavelengths of light, which allows a plant to get as much energy as possible from a single light source.

After absorbing photons, the electrons contained in the pigments become excited and increase their energy level. Accessory pigments such as carotenoids, anthocyanins, and xanthophylls can then pass on this energy to primary pigments like chlorophyll a, which can oxidize and donate an electron to the electron transport chain in the light-dependent reaction.

Photosynthetic Pigments - Key takeaways

Chromatography is a useful method to investigate the different photosynthetic pigments present in leaves. This involves isolating the pigments in a solution and then using filter paper to separate each pigment. We can identify different pig using an Rf value, which can be calculated from the distance each pigment has travelled on the. for the R value:

Depending you include Chlorophyll a and Chlorophyll b, Carotenoids, Xanthophylls, and Anthocyanin. Chlorophyll a is likely to be the most abundant pigment. Photosyntheticments are crucial to photosynthesis as they absorb photons (waves of light) at certain wavelengths. Different pigments can absorb and reflect different wavelengths of light, which allows a plant to get as much energy as possible from a single light source. By understanding the different pigments present in a leaf, we can gain insight into the plant's photosynthetic abilities and adaptations.

Photosynthetic Pigments

How does chromatography separate pigments?

Photosynthetic (or other ones investigated) pigments will have different relative solubulities. This means that the pigments will move at a different rates in the media (e.g. paper). 

What is chromatography?

Chromatography is a lab technique that separates a mixture by passing it through a solution that allows the different mixture components to move at different rates.

What are 3 main types of photosynthetic pigments?

Chlorophyll a, Chlorophyll b and carotenoids.

Where are photosynthetic pigments found? 

Photosynthetic pigments are found in chloroplasts or in photosynthetic bacteria. 

What are photosynthetic pigment molecules? 

They are pigments that can absorb light from the sun for photosynthesis.

Join Shiken For FREE

Gumbo Study Buddy

Try Shiken Premium
for Free

14-day free trial. Cancel anytime.
Get Started
Join 20,000+ learners worldwide.
The first 14 days are on us
96% of learners report x2 faster learning
Free hands-on onboarding & support
Cancel Anytime