Cell Biology and Structure

These are extremely minute hair like appendages. They are made up of a protein called pilin. They help in the attachment of a bacterial cell. They also act as conjugation canals through which DNA of one cell passes into the other.

Within the cells of basidiomycete fungi are found microscopic structures called parenthesomes or septal pore caps. They are shaped like parentheses and found on either side of pores in the dolipore septum which separates cells within a hypha.

The part of the cell which occurs between the plasma membrane and nuclear envelope is called the cytoplasm. The cytoplasm is composed of the matrix, the organelles and non-living inclusions like vacuoles and granules.

Being a dynamic structure, it is quite flexible. Hence, it does not restrict growth, movements, and changes in the shape of a cell.

The cell membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively-permeable to ions and organic molecules and controls the movement of substances in and out of cells. It consists of the phospholipid bilayer with embedded proteins.

Guard cells have thin and elastic outer walls and thick inner walls. When turgid, the thin outer walls stretch and bulge outward, opening the stomatal pore. This asymmetric thickening is essential for stomatal opening and closing.

Each stoma (stomatal pore) is surrounded by two specialized guard cells that change shape to open or close the pore. This regulates gas exchange and water loss.

Lysosomes are single membrane-bound organelles containing digestive enzymes. The nucleus has a double membrane (nuclear envelope), mitochondria and chloroplasts also have double membranes, making lysosome the correct answer.

Animal cells are of two types, eukaryotic, which contain a nucleus, and prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular.

 The rod-shaped structures in the nucleus of a cell are chromosomes. They carry genetic material in a 'rod' of DNA that is bonded to various proteins in the cell nucleus.

The primary cell wall of plants is composed of the polysaccharides cellulose, hemicellulose and pectin.

Cytoplasm is the jelly-like, water-based substance that fills the cell and surrounds organelles. It provides the medium for metabolic reactions and organelle movement.

Plant cells differ from animal cells in the presence of a large central vacuole.

The nucleoid is the nuclear region in prokaryotic cells where the genetic material (DNA) is located, but it is not surrounded by a nuclear membrane. Nucleolus is found within eukaryotic nuclei, while vesicles and cisternae are membrane-bound structures in eukaryotes.

The nucleus contains the cell's genetic material (DNA) and controls all cellular activities, including growth, development, and protein synthesis, thereby determining how the cell develops and what form it takes. Vacuoles store materials, mitochondria produce energy, and plastids (in plants) have specific functions like photosynthesis or storage.