What Is The Function Of Thylakoid

Thylakoid is the site of photochemical or light-dependent reactions of photosynthesis. It contains chlorophyll which absorbs energy from the sunlight and is involved in the formation of ATP and NADPH in the light reaction of photosynthesis through electron transport chains. As a result, light energy is converted into chemical energy.

The process of water oxidation or photolysis of water during photosynthesis results in the release of oxygen.

Thylakoids are membranous sacs located within the chloroplast. The thylakoid membrane contains chlorophyll and multiple thylakoids are attached together to form a stack of discs called grana.

Thylakoid Structure and Function

Thylakoids are present in the chloroplasts of all plants and blue-green algae. These disc-like sacs of the internal membrane system of the chloroplast are interconnected and found suspended in the stroma.

Chloroplast structure

Thylakoids are arranged in a stack known as Grana. The thylakoid membrane contains the photosynthetic pigment Chlorophyll, which absorbs the sunlight and is essential for the process of Photosynthesis.

The main characteristics of thylakoids are:

  • Involved in the light-dependent reactions of photosynthesis
  • Contain the photosynthetic pigment chlorophyll
  • Form stacked structures called grana
  • Contain molecules of the green pigment chlorophyll
  • Contain enzymes to catalyze the light-dependent reactions of photosynthesis

Each thylakoid is a sac that is bounded by a membrane and is situated within the stroma of chloroplasts.

Grana are stacks of thylakoids, resembling a stack of coins. They are where the light reactions of photosynthesis take place.

The stroma lamellae connects the thylakoids of two different grana.

The thylakoid is composed of a thylakoid membrane and a thylakoid lumen.

Thylakoid Membrane

The Thylakoid Membrane encloses the innermost compartment, the Thylakoid Lumen. It is composed of Phospholipids and Galactolipids, and is similar to the inner membrane of chloroplasts, as well as sharing characteristics with the prokaryotic membranes of Cyanobacteria. Additionally, the Thylakoid Membrane contains Chlorophyll and other Photosynthetic Pigments.

Learn More About Bacterial and Plant Photosynthesis Here

The thylakoid membrane contains numerous integral membrane proteins.

Photosystem I is mostly located in the stroma lamellae and outer thylakoids of grana. It has a light-harvesting complex with a reaction centre (chlorophyll a) that has a maximum absorption at 700 nm (P700). This photosystem is involved in both cyclic and non-cyclic photophosphorylation.

Photosystem II is mostly present in the grana thylakoids and consists of a light-harvesting complex with a reaction center (chlorophyll a) that has maximum absorption at 680 nm (P680). It is involved in non-cyclic photophosphorylation and is associated with a water splitting complex.

The Cytochrome B6f complex is evenly distributed and is a part of the electron transport chain.

ATP Synthase is mostly present in the stroma lamellae and outer thylakoids of grana. The CF0 subunit forms the transmembrane channel and is embedded in the thylakoid membrane. The CF1 subunit is located towards the stroma and catalyses ATP synthesis.

Thylakoid Lumen

The Thylakoid lumen is the innermost aqueous compartment of the chloroplast, enclosed by a thylakoid membrane. It is an important player in the ATP synthesis or phosphorylation driven by chemiosmosis, as protons are pumped across the membrane into the lumen, creating a concentration gradient across the thylakoid membrane.

The water-splitting complex is present at the inner side of the thylakoid membrane of PS II and results in the release of protons and oxygen produced by splitting of water into the thylakoid lumen.

The Thylakoid lumen also contains plastocyanin, which is an electron transport protein and shuttles electrons from cytochrome B6f complex to PS I.

Frequently Asked Questions

What are Thylakoids?

Thylakoids are membrane-bound organelles found in the chloroplasts of plants and algae. They are the site of photosynthesis, where light energy is converted into chemical energy in the form of ATP and NADPH.

Thylakoids are membrane-bound structures found inside chloroplasts and cyanobacteria. They consist of a thylakoid membrane which encloses the innermost thylakoid lumen.

The function of Thylakoids is to capture light energy during photosynthesis and convert it into chemical energy.

Thylakoids are the primary location for the light-dependent reactions of photosynthesis. Furthermore, they are involved in the photolysis of water, which results in the release of oxygen during photosynthesis.

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