cellgrowth

Cell growth is the process by which cells increase in size or number. In unicellular organisms, growth usually means population expansion through cell division. In multicellular organisms, growth encompasses both hypertrophy (increase in cell size) and hyperplasia (increase in cell number), and it supports development, tissue maintenance, and healing.

Growth is regulated by the cell cycle and a network of signaling pathways. In eukaryotic cells, progression through G1, S, G2, and M phases depends on cyclins and cyclin-dependent kinases, with checkpoints ensuring readiness. External signals from growth factors, nutrients, and energy status activate pathways such as MAPK, PI3K/AKT, and mTOR, which promote biosynthesis and division.

Environmental and physical factors influence growth. Nutrient availability, oxygen, temperature, and cell density can accelerate or restrain proliferation. Mechanisms like contact inhibition help maintain tissue architecture. In plants, cell growth frequently involves cell expansion driven by turgor pressure and cell wall loosening. Measurement in laboratories uses growth curves, doubling time, and assays of DNA synthesis or metabolic activity.

Applications and relevance: understanding cell growth informs developmental biology, cancer research, and regenerative medicine. Dysregulation of growth processes underlies tumor formation and aging. Studying how cells sense and respond to their environment helps in tissue engineering, agriculture, and biotechnology.