Living organisms are made up of cells that can be classified into two main types: prokaryotic and eukaryotic cells. These fundamental building blocks of life have distinct characteristics that set them apart.
Prokaryotic cells are simpler and smaller, typically found in bacteria. They lack a true nucleus and membrane-bound organelles. Their genetic material floats freely in the cytoplasm within a region called the nucleoid. The cell wall contains peptidoglycan, and they may have additional structures like flagella for movement or pili for attachment. Common prokaryotic cell examples include bacteria like E. coli. In contrast, eukaryotic cells are more complex and larger, found in plants, animals, fungi, and protists. They contain a true membrane-bound nucleus housing their DNA, along with specialized organelles like mitochondria for energy production, endoplasmic reticulum for protein synthesis, and Golgi apparatus for protein packaging and secretion.
Within multicellular organisms, cells become specialized to perform specific functions. For example, in specialised animal cells, muscle cells are adapted with multiple nuclei and abundant mitochondria to provide energy for contraction. These adaptations of muscle cells enable them to perform their function efficiently. Other specialized cells include nerve cells with long axons for transmitting signals, red blood cells that lack a nucleus to maximize hemoglobin storage, and sperm cells with a tail for swimming. The study of cell structure and function is fundamental to GCSE Biology and forms a crucial part of Biology Paper 1 topics. Understanding these concepts helps explain how organisms function at the cellular level and how different cell types work together in complex multicellular organisms.