NOTES: Introduction to the Cell

1.All living things are composed of 1 or more cells. 2.In organisms, cells are the basic unit of structure & function 3.Cells are produced only from existing cells.

MICROSCOPES 1.Light Microscope 2.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 x

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 1.Scanning Electron Microscope –electron beam scans the surface of a specimen –useful for studying the surface of specimen in 3-D 2.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

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!!!

PROKARYOTESEUKARYOTES oldest cells (3.5 billion years) “newer” cells (1.5 billion years)

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

PROKARYOTESEUKARYOTES 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

PROKARYOTESEUKARYOTES 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

PROKARYOTESEUKARYOTES 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 ( µm)

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