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Sreeshan · 2024-01-11T02:14:24.069Z

BUILDING BLOCKS OF LIFE — CELL AND TISSUES Basic 2 types of cells prokaryotic cells and eukaryotic cells. Prokaryotic cells A prokaryotic cell is a cell that lacks a true nucleus and membrane-bound organelles. Features: • No nucleus: Unlike their eukaryotic counterparts, prokaryotes lack a true nucleus. Their genetic material (DNA) is not enclosed in a membrane but simply floats freely in the cytoplasm. • Simple internal structure: Prokaryotic cells have a minimal internal structure, with ribosomes responsible for protein synthesis and a cell membrane regulating the movement of materials in and out. • Smaller and simpler: Generally ranging from 0.5 to 5 micrometers, these single-celled organisms are significantly smaller than most eukaryotic cells. This allows for faster reproduction and efficient resource utilization. • Diverse metabolic capabilities: Despite their simplicity, prokaryotes exhibit incredible metabolic diversity. They can be found in extreme environments like boiling springs or deep ocean trenches, and utilize various energy sources like sunlight, chemicals, and organic matter. Classification: • Bacteria: The most common and diverse, including familiar "germs" like E. coli and Bacillus. Bacteria can be further classified based on their shape (rod, spiral, coccus) and metabolic needs (aerobic, anaerobic). • Archaea: Found in extreme environments like deep-sea vents and hypersaline lakes, archaea have unique cell wall structures and often use unusual energy sources like methane or hydrogen sulfide. Ecological importance: • Decomposition: Breaking down dead organisms and returning nutrients to the soil. • Nitrogen fixation: Converting atmospheric nitrogen into a usable form for plants. • Antibiotic production: Many antibiotics come from bacteria, helping us fight off infections. • Food production: Certain bacteria help in food fermentation, like yogurt and cheese production. Eukaryotic cells Eukaryotic cells are the building blocks of all animals, plants, fungi, and many protists. Unlike their simpler prokaryotic counterparts, they boast a complex internal structure and specialized compartments called organelles, each with its own dedicated function. Features: • Nucleus: The control center, housing the cell's genetic material (DNA) in the form of chromosomes. The nucleus is surrounded by a double membrane, regulating the movement of genetic material and ensuring its protection. • Organelles: Specialized compartments with dedicated functions, performing tasks like energy production, protein synthesis, waste disposal, and transportation. Some key organelles include: • Mitochondria: The powerhouses of the cell, generating energy through cellular respiration. • Endoplasmic reticulum (ER): A network of membranes responsible for protein synthesis and transport. • Golgi apparatus: Modifies and packages proteins and lipids for secretion or transport within the cell. • Lysosomes: Contain digestive enzymes that break down cellular waste and foreign particles. • Cytoskeleton: A network of protein fibers providing structural support, facilitating movement, and enabling cell division. • Plasma membrane: The outer boundary of the cell, controlling the movement of materials in and out. Diversity and Specialization: Eukaryotic cells exhibit incredible diversity in size, shape, and function. For example, a tiny red blood cell lacks a nucleus and is specialized for oxygen transport, while a nerve cell can be several meters long and intricately branched for rapid signal transmission. This allows different cell types to excel at specific tasks, ultimately contributing to the complex organ systems and functions of multicellular organisms. Evolutionary Significance: The emergence of eukaryotic cells marked a major evolutionary leap, paving the way for the development of complex multicellular organisms. Their sophisticated internal organization and compartmentalization enabled efficient metabolic processes, diverse cellular specializations, and ultimately, the incredible diversity of life we see today.