Thylakoid Membrane

Thylakoid is a membrane-bound compartment found inside cyanobacteria and chloroplasts. They consist of a thylakoid membrane surrounding a thylakoid lumen. Thylakoids are the site wherein the light-dependent reactions of photosynthesis occur. Thylakoids found in chloroplasts are normally stacks of disks that are refered to as grana or granum.  Grana are linked by stroma thylakoids or intergrana, which join granum stacks together in order to form a single functional compartment.

The formation of thylakoids requires light. In the plant embryo with absence of light, the proplastids form into etioplasts, this contains semicrystalline membrane structure known as prolamellar bodies. Those prolamellar bodies develop into thylakoids when exposed to light and this does not happen in seedlings that have been grown in the dark, as they undergo etiolation. Thylakoids fail to develop due to underexposure to light, and once the production of chloroplast fail, this results to the death of the plant. Thylakoids contain numerous peripheral and integral membrane proteins, as well as luminal proteins.

Light reaction

The light-dependent reaction or simply the light reaction, known as the first part of the photosynthetic process, takes place in the thylakoids. Thylakoids are stacked together like coins, and are being connected to one another by the stroma lamellae, a part of the thylakoid membrane. The light-dependent reactions of photosynthesis take place in thylakoids. Such process includes light-driven water oxidation as well as oxygen evolution, which is the pumping of protons across the thylakoid membranes coupled with the electron transport chain of the photosystems and cytochrome b6f complex, and ATP synthesis by the ATP synthase utilizing the generated proton gradient.

The said process is generally where the plants’ color comes from. The outer surface is referred as the photosynthetic membrane or the thylakoid membrane and the pigment and ATP synthetase molecules are inside the membrane of the thylakoid space, on the thylakoid membrane.

©2005-2015 Plant Biology Advice - Dean Ravenscroft