Grana are the locations of the photosynthetic light response. Grana are disc-shaped plates that contain a pigment system composed of chlorophyll-a, chlorophyll-b, carotene, and xanthophyll.
Granum is the fundamental structural unit of the chloroplast thylakoid membrane network. It is constructed of numerous flattened membranes layered in a cylindrical configuration.
Grana membranes consist of lipids and pigment-protein complexes whose principal function is to catalyze photosynthetic light processes.
These membranes are extremely dynamic structures that may adapt to changing environmental circumstances by fine-tuning photochemical efficiency, as demonstrated by the structural rearrangement of grana stacks.
Due to the nanoscale size of the structural granum features, high-resolution electron microscopic methods are required to examine the granum architecture comprehensively.
This mini-review examines new quantitative grana structural studies from electron microscopy data, focusing on human measurements and semi-automated procedures.
We describe and define structural characteristics utilized by many publications, such as granum height and diameter, thylakoid thickness, end-membrane length, Stacking Repeat Distance, and Granum Lateral Irregularity.
This paper also provides insights into the efficient and successful measurements of 2D micrographs of grana stacks.
Also included is guidance on how to accurately interpret the collected data, considering the 3D character of the grana stacks projected onto the 2D space of the electron micrograph.
Grana ultrastructural investigations show crucial characteristics of this interesting membrane structure, expanding our understanding of the amazing adaptability of the thylakoid network.
How Do Grana Work?
Everyone needs photosynthesis. That is, everyone is living on Earth’s surface. The conversion of light into food energy is the basis of practically all food chains on Earth and the means of subsistence for plants and algae.
These creatures include chloroplasts, the energy-producing organelles responsible for photosynthesis within their cells. Within chloroplasts, there are several grana.
Grana (plural of ‘granum’) are stacks of structures known as thylakoids, which are little membrane disks on which light-dependent photosynthetic processes occur. The form of the thylakoids, which are stacked into grana, maximizes the amount of photosynthesis that may take place.
The grana resemble stacks of green pancakes within the chloroplast, and their height and distribution are not uniform.
Lamellae, or membranes that connect the grana and participate in the photosystem 1 stage of photosynthesis, link the grana together. Stroma, a liquid suspension, surrounds all chloroplast components.
Function Of Grana
Grana’s thylakoids contain essential pigments that absorb light, such as chlorophyll. When light strikes these pigments in photolysis, they split water and release oxygen as a byproduct.
The electrons liberated by this process arrive at photosystem 2 and are transported to photosystem 1 through an electron transport chain. Here, they undergo a second electron transport chain after being further stimulated by light absorption.
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