Sejtek

Sejtek, the Hungarian term for cells, are the basic units of life and the smallest units capable of independent biological activity. They form the structure of all organisms and carry the genetic material and metabolic machinery required for growth, replication, and response to the environment.

Cell theory states that all living things are composed of cells, that cells are the fundamental units of structure and function, and that new cells arise only from preexisting cells. This framework underpins modern biology and medicine.

Cells are divided into prokaryotic and eukaryotic types. Prokaryotes such as bacteria lack a defined nucleus and membrane-bound organelles. Eukaryotes, including plants, animals, fungi, and protists, have a nucleus and numerous membrane-bound organelles.

All cells share a plasma membrane, cytoplasm, and genetic material. Eukaryotic cells contain organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus; chloroplasts are present in plants and some algae. Most genetic material is DNA, with some organelles carrying their own DNA.

Plant cells differ from animal cells in having cell walls, chloroplasts, and a large central vacuole. Animal cells lack cell walls and chloroplasts but share many other organelles.

Sejtek range from unicellular organisms that perform all life processes alone to multicellular organisms with specialized cell types that form tissues and organs through differentiation.

Cell division occurs by mitosis in most somatic cells and by meiosis in germ cells; bacteria reproduce by binary fission. Genetic variation arises through mutation and genetic exchange in microbes, and through meiosis and recombination in sexually reproducing organisms.

Understanding sejtek is central to biology, medicine, and biotechnology, influencing development, disease research, and therapeutic strategies.