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In certain bacteria like Bacillus subtilis, the plasma membrane creates inward folds, known as mesosomes, that extend into the cytoplasm. These mesosomes perform various roles such as respiration and secretion.

1. (a) The glycocalyx, also called mucilage, forms the outermost layer of bacterial cells or their cell walls and is rich in polysaccharides. A dense and rigid mucilage layer, known as a capsule, provides stickiness to the cells and shields them from desiccation, toxins, and attachment by external invaders.
2. (b) The capsule is an outer layer surrounding the bacterial cell wall. It helps protect the cells from being engulfed by eukaryotic cells like macrophages and also blocks bacterial viruses and hydrophobic toxic substances such as detergents.
3. (c) The cell membranes of E. coli, a bacterial species, and Chlamydomonas, a unicellular green alga, are similar in composition, as both are made up of lipids and proteins.
4. (d) Nostoc is classified as a prokaryote, whereas the others are eukaryotes. Prokaryotes lack a nuclear membrane.

Correct answer: (a) The glycocalyx, also called mucilage, forms the outermost layer of bacterial cells or their cell walls and is rich in polysaccharides. A dense and rigid mucilage layer, known as a capsule, provides stickiness to the cells and shields them from desiccation, toxins, and attachment by external invaders.

Solution

The correct choice identifies the glycocalyx/capsule, which is an outer bacterial layer made largely of polysaccharides. It helps cells adhere and protects them from drying out, toxins, and other harmful agents.

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