cellorganisation

Cell organisation refers to how cells are structured and arranged to carry out life processes. In biology, organisms are built from cells that fall into two broad categories: prokaryotic and eukaryotic. Prokaryotic cells, such as bacteria, lack a membrane-bound nucleus and most organelles. Their DNA is typically a circular chromosome in the cytoplasm, and they have a cell membrane, a rigid cell wall, ribosomes, and often external structures like flagella or pili.

Eukaryotic cells, found in plants, animals, fungi, and protists, are more compartmentalised. They possess a true nucleus that houses DNA, enclosed by a nuclear envelope. The cytoplasm contains cytosol and a cytoskeleton of protein filaments. Membrane-bound organelles include mitochondria for energy production, chloroplasts in photosynthetic cells, the endoplasmic reticulum (rough for protein synthesis, with ribosomes; smooth for lipid synthesis), the Golgi apparatus for processing and packaging, lysosomes and peroxisomes for digestion and metabolism, and various vesicles. The plasma membrane regulates exchange with the environment and provides cell signalling opportunities. The vacuole, especially large in plant cells, stores water and nutrients.

Cell organisation extends beyond organelles to tissues and organ systems in multicellular organisms. Cells differentiate to perform specialised functions and interact through signalling molecules and the extracellular matrix. The cell cycle and division (mitosis in somatic cells, meiosis in germ cells) enable growth, development, and genetic propagation, while controlled apoptosis helps remove damaged cells.