NOTES: 7.1 - Introduction to the Cell

Cell Theory All living things are composed of 1 or more cells. Cells are the basic unit of structure & function in living things. New cells are produced from existing cells.

MICROSCOPES Light Microscope Electron Microscope (1940’s) Scanning Electron Microscope Transmission Electron Microscope

Light Microscope works by passing visible light through a thin section of specimen and then through glass lenses magnification about 1000x - 1500x

Electron Microscope (1940’s) uses electron beams which have shorter wavelengths of light (so you can see smaller objects…more detail) magnification up to 500,000x

Electron Microscope Scanning Electron Microscope electron beam scans the surface of a specimen useful for studying the surface of specimen in 3-D Transmission Electron Microscope electrons transmitted through specimen used to study internal cell structure

Disadvantages to EM… can only view dead cells (preparation steps kill living cells) very expensive zooxanthellae cells cultured from coral Aiptasia pulchella in a Scanning Electron Microscope

Cell Types & Classification!

ALL CELLS: have a cell membrane have cytoplasm have ribosomes can reproduce & contain genetic material

CELLS CAN BE CLASSIFIED AS: 1. PROKARYOTES 2. EUKARYOTES See… no nucleus!!! See… a nucleus!!!

PROKARYOTES EUKARYOTES oldest cells (3.5 billion years) “newer” cells (1.5 billion years)

PROKARYOTES EUKARYOTES oldest cells (3.5 billion years) single celled “newer” cells (1.5 billion years) single or multicellular

PROKARYOTES EUKARYOTES oldest cells (3.5 billion years) single celled lack nucleus & membrane-bound organelles “newer” cells (1.5 billion years) single or multicellular have a “true” nucleus & membrane-bound organelles

PROKARYOTES EUKARYOTES oldest cells (3.5 billion years) single celled lack nucleus & membrane-bound organelles genetic material in a single, circular molecule “newer” cells (1.5 billion years) single or multicellular have a “true” nucleus & membrane-bound organelles genetic material organized and in nucleus

PROKARYOTES EUKARYOTES oldest cells (3.5 billion years) single celled lack nucleus & membrane-bound organelles genetic material in a single, circular molecule small (1-2 µm) “newer” cells (1.5 billion years) single or multicellular have a “true” nucleus & membrane-bound organelles genetic material organized and in nucleus larger (2-1000 µm)

PROKARYOTES EUKARYOTES oldest cells (3.5 billion years) single celled lack nucleus & membrane-bound organelles genetic material in a single, circular molecule small (1-2 µm) Domains Bacteria & Archaea (bacteria) “newer” cells (1.5 billion years) single or multicellular have a “true” nucleus & membrane-bound organelles genetic material organized and in nucleus larger (2-1000 µm) Kingdoms Protista, Fungi, Plantae, Animalia

NUCLEUS • membrane-bound organelle in eukaryotic cells; • contains the cell’s DNA enclosed by a nuclear envelope contains all of the information for cell to function