Cell Structures: Organelles, Bacteria, Viruses, and Fungi
Cell Structures and Components
Nuclear membrane: A double membrane that surrounds the nucleus of the cell. It contains small pores that allow communication between the nucleus and the cytoplasm.
Chromosomes: Immersed in the nuclear fluid, they become visible only when the cell begins to divide. Chromosomes are carriers of genes, the factors responsible for the transmission of hereditary traits. Their number varies across different cell types and species. Generally shaped like elongated filaments, they are composed mainly of proteins and nucleic acids.
Nucleoli: Spherical corpuscles consisting primarily of protein and RNA.
Cell wall: A thick membrane with varying physical and chemical characteristics. It often gives the cell rigidity and consistency while providing elasticity to withstand deformation without breaking. (Primarily in plant cells).
Plasma membrane: A thin membrane that surrounds the cell, featuring tiny pores that allow communication between the cytoplasm and the exterior.
Plasmodesmata: Robust connections, appearing as very fine cytoplasmic channels, that connect neighboring cells (in plants).
Plastids: Organelles of plant cells, often having a varied rounded shape. Among the most important are chloroplasts.
Vacuoles: Often a characteristic attribute of plant cells, they are close to the center, near the nucleus, sometimes occupying the Golgi apparatus area.
Lysosomes: Tiny sacs filled with digestive enzymes, possibly used in processes such as nutrient breakdown before use.
Mitochondria: Organelles involved in cellular respiration.
Endoplasmic Reticulum and Other Organelles
Endoplasmic Reticulum (ER): A network of thin, double membranes that traverse all areas of the cytoplasm and connect with the cell membrane.
Golgi Apparatus: Stacked layers of very thin membranes; its function is to elaborate the secretions of the cell.
Ribosomes: Very small organelles, often grouped to form polyribosomes. This is where the cell manufactures its proteins.
Microorganisms: Bacteria, Viruses, and Fungi
Bacteria: Prokaryotic cells containing DNA arranged in a circular chromosome within the cytoplasm. They are very small. Bacteria are formed by a cytoplasm and a nucleus. The membrane is thick and chemically constituted by murein (a type of peptidoglycan).
Classification (based on shape):
- Cocci: Spherical, sometimes slightly oval.
- Bacilli: Elongated.
- Spirilla: Comma or spiral-shaped.
Viruses: The simplest vital units, differing structurally from prokaryotic cells. They can be polyhedral, cylindrical, or complex. They have a protein capsule surrounding a molecule of nucleic acid, which facilitates attachment and penetration into the host cell.
Fungi: Eukaryotic cells. They can be beneficial or harmful to health.
Types of Fungi:
- Ascomycetes: Such as yeasts, important in fermentation (beer, wine, yogurt).
- Phycomycetes: Develop out of water, although some are parasites of aquatic animals and plants (e.g., bread mold).
- Basidiomycetes: Mushrooms.
Yeast: Unicellular ascomycetes that play an important role in fermentation processes.