सामान्य कृषि एवं कोशिका जीवविज्ञान

Universality of cell structures across prokaryotes:

• Ribosomes (specifically 70S ribosomes consisting of 50S and 30S subunits) are indispensable for protein translation and are universally present in all living prokaryotes (eubacteria and archaea).
• Capsules (glycocalyx layers) are present only in specific encapsulated bacteria (e.g., Streptococcus pneumoniae) and are absent in non-capsulated species.
• Flagella are motility appendages present only in motile bacteria; non-motile prokaryotes lack flagella entirely.

Organelles of plant lipid metabolism:

• Glyoxysomes are specialized single-membrane microbodies found in lipid-storing tissues (such as the endosperm or cotyledons of oilseeds like castor, sunflower).
• They contain the enzymes of the glyoxylate cycle (isocitrate lyase, malate synthase) and $\beta$-oxidation of fatty acids, converting stored triacylglycerols into succinate and subsequently carbohydrates (gluconeogenesis) during germination.
• They are intimately associated with oleosomes/oil bodies (spherosomes).

Structure of plasmodesmata:

• Plasmodesmata are microscopic channels traversing the cell walls of plant cells, facilitating symplastic communication and transport.
• Running through the center of each plasmodesma is a narrow, cylindrical appressed tubule called the desmotubule.
• The desmotubule is a continuous extension of the cortical endoplasmic reticulum (ER) network from one cell to the adjacent cell.
• Around the desmotubule lies the cytoplasmic sleeve bounded by the plasma membrane.