Pyrenoids are related to:
a) Starch formation
b) Protein storage
c) Enzyme secretion
d) General metabolism

Starch Formation:
Pyrenoids are specialized structures found within the chloroplasts of certain algae, particularly in the green algae and some diatoms. They are primarily involved in the process of starch formation. Starch is a complex carbohydrate that serves as an energy storage molecule in plants and algae. Pyrenoids contain enzymes and other proteins that are involved in the synthesis and accumulation of starch. These structures play a crucial role in the carbon fixation process during photosynthesis, where carbon dioxide is converted into starch.

Protein Storage:
In addition to starch formation, pyrenoids also function as sites for protein storage. Pyrenoids accumulate various proteins that are important for the growth and development of the algae. These proteins can include enzymes, structural proteins, and regulatory proteins that are required for various metabolic processes within the cell.

Enzyme Secretion:
Pyrenoids are involved in enzyme secretion, particularly for carbon dioxide fixation. They contain enzymes such as Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase), which plays a crucial role in the conversion of carbon dioxide into organic compounds. Rubisco catalyzes the first step of the Calvin cycle, a series of reactions that leads to the production of sugars. Pyrenoids provide a localized environment for the concentration of Rubisco and other enzymes involved in carbon fixation.

General Metabolism:
Pyrenoids are integral to the overall metabolism of algae. They are involved in various metabolic processes, including carbon fixation, starch synthesis, protein storage, and enzyme secretion. These structures help regulate the concentration of key enzymes and proteins necessary for the proper functioning of the cell. Pyrenoids ensure efficient utilization of carbon dioxide and energy resources, allowing algae to thrive and grow in their environments.

In conclusion, pyrenoids are specialized structures within algae that play a critical role in starch formation, protein storage, enzyme secretion, and general metabolic processes. They are essential for the efficient utilization of carbon dioxide and the production of energy-rich molecules necessary for the growth and survival of algae.

Protein storage in green algae. But it also store strach. As per NCERT sentence (pyrenoids store protein besides of strach)