What are photosystems and reaction centres, and what is their function?

Photosystems are clusters of pigments embedded in thylakoid membranes.


Each photosystem has a light-harvesting system that captures light energy and transfers it to a reaction centre, which contains two molecules of chlorophyll a. These molecules absorb energy and emit high-energy electrons that drive photosynthesis.

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What is an absorption spectrum in the context of photosynthesis?

An absorption spectrum is the range of wavelengths absorbed by the pigments in a chloroplast.

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What is the Rf value, and how is it calculated?

The Rf value is a number that indicates how far a substance, like a photosynthetic pigment, travels during chromatography.


It is calculated as:


Rf​=distance travelled by solvent from the origindistance travelled by pigment from the origin​


Chromatography, and the Rf values generated from it, can be used to identify the different pigments in chloroplasts.

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What is an action spectrum in the context of photosynthesis?

An action spectrum is a graph showing the rate of photosynthesis at different wavelengths of light.

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What are some of the other photosynthetic pigments, and why are they needed?

Some other photosynthetic pigments include chlorophyll b, xanthophylls, and carotenoids.


These photosynthetic pigments absorb different wavelengths of light than those absorbed by chlorophyll a.

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What is the main pigment in photosynthesis, and why does it make many plants appear green?

The main pigment in photosynthesis is chlorophyll a.


Most plants appear green because chlorophyll a mainly absorbs red and blue light wavelengths and reflects green light wavelengths.

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What is the role of photosynthetic pigments?

Photosynthetic pigments absorb energy from certain wavelengths of light.

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What is the stroma?

The stroma is a fluid-filled matrix in a chloroplast where the light-independent stage of photosynthesis takes place.

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What are grana, thylakoids, and lamellae?

Grana are stacks of flattened sacs called thylakoids. Some thylakoids are joined by membranous extensions called lamellae.


The thylakoid membranes contain complexes of pigments that absorb light for photosynthesis. The light-dependent stage of photosynthesis takes place in the thylakoids. 

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Do chloroplasts have a single membrane or a double membrane?

A chloroplast is surrounded by two membranes.

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What is the main function of chloroplasts, and where are they usually found?

Chloroplasts are the site of photosynthesis.


Chloroplasts are found in some algae and plant cells. In plants, they are mainly in mesophyll tissues in leaves.

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