cells

• modern cell theory:

  • the cell is the smallest living unit in all organisms
  • all living things are made of cells
  • all cells come from pre-existing cells
• cells are the basic and fundamental unit of life, possessing a highly organised structure that enables it to carry out vital functions
• every living organism is made of cells
• unicellular: a microscopic single-celled organism, e.g. bacteria, amoeba
• multicellular: macroscopic organisms with more than one cell type, e.g. humans
• prokaryotes:

  • unicellular
  • no nucleus
  • has DNA
  • no membrane bound organelles
• eukaryotes:

  • multicellular
  • has a nucleus and DNA
  • has membrane bound organelles
• the first cell: LUCA (Last Universal Common Ancestor), believed to be a prokaryotic cell that existed around 3.5-4 billion years ago
• specialised cell > tissue > organ > system > organism
• every cell needs oxygen and nutrients to live
• carbon dioxide is waste for a cell
• every cell needs blood flow to live