Microscopes Provide the Windows to the World of the Cell The Cell Theory Microscopes Provide the Windows to the World of the Cell

The Men Anton Van Leeuwenhoek (1600’s) Credit for the first microscope Looked at pond water and saw “wee beasties”

Robert Hooke Observed plant stems, wood, and cork (1600’s) Saw all the tiny chambers and called them CELLS What cell part did Hooke observe? Cell Wall

Robert Brown (1833) Observed that cells had a dark structure within plant cells Brown observed the nucleus

Matthias Schleiden (1838) Stated that all plants are made of Cells Made many observations of plants around the area

Theodor Schwann (1839) Stated that all animals are made of Cells Observed many animal tissues

Rudolf Virchow (1855) Stated that all cells come from pre-existing cells Cells arise from the division of pre-existing cells

The Cell Theory All living things are composed of cells Cells are the basic unit of structure and function in living things All cells come from pre-existing cells

Exceptions to the Cell Theory Viruses – are not cellular Mitochondria and chloroplast – each contain genetic material and can reproduce

Endosymbiotic Theory What is this? Concerns the origins of mitochondria and plastids (chloroplasts) from prokaryotic cells Endosymbiont Cell that lives within another cell

Endosymbiotic Theory Endosymbionts gained entry to cell as undigested prey items or parasites and began a mutually beneficial relationship Occurred by endocytosis (cell parts are engulfed) Over time this would turn into a single organism whose parts are inseparable

Endosymbiotic Theory Evidence Mitochondria & Plastids Have enzymes and transport systems that are the same as in plasma membrane of prokaryotes Also replicate by same process as certain prokaryotes

Endosymbiotic Theory Evidence Cont’d Both organelles have DNA, have mechanisms to transcribe /translate proteins Size, Nucleotide Sequence, & Sensitivity to antibiotics are similar to prokaryotes