Cells were not discovered until the mid-1600’s when microscopes were invented. Robert Hooke: first man to describe cells He looked at a slice of cork He described it as “ little boxes” or “little rooms”
He described plant cells as “juicy”, which meant that they were livingHe discovered that animal cells do not have a cell wall like plant cells do.
Anton van Leewenhoek: made his own microscope to look at pond scum Saw little organisms that we now call protists Discovered differences in blood cells Discovered that yeast were unicellular organisms
Almost 200 years passed before scientists realized that cells were present in ALL living things! Matthias Schleidan: Concluded that all plants were made of cells Theodor Swann: Concluded that all animals were made of cells
Wrote the first two parts of the cell theory, which is: (1) All organisms are made up of one or more cells (2) The cell is the basic unit of all living things *Rudolf Vichrow: Wrote 3rd part of Cell Theory, which is: (3) All cells come from existing cells
Cell Size: Example of large cell: yolk of chicken egg Most cells are SMALL. There are reasons why: (1) Allows the cell to get rid of less food and wastes (2) As the volume of the cell increases, its surface area grows (3) The volume and surface area of the cell limit the size that the cell can be. (4) We calculate this by finding the surface area-to-volume ratio
RATIO = surface area / volumeExample:Step 1: Find surface area of cube (# of sides x area of cube)If sides of cube measure 2 cm, then surface area = 6 x (2 cm x 2 cm)Surface area of cube = 24 cm2
Step 2: Find volume of a cube(side x side x side)Volume = 2 cm x 2 cm x 2 cmVolume of cube = 8 cm3Put numbers into equation: 24 = 3: 1 8 “three to one ratio” *The larger the cell, the smaller the surface area to volume ratio!
Two Kinds of CellsProkaryotes: single-celled organisms that do not contain a nucleusPRO = NO (NUCLEUS) *no membrane-bound organelles *Smaller in size *Examples: Eubacteria and Archabacteria *They do contain cytoplasm, DNA, and a cell membrane
Eukaryotes: single or multicellular organisms that DO contain a nucleus *Have membrane-bound organelles *Most are larger in size, but still require a microscope to see *Examples: protists, fungi, plants, and animals *They do contain cytoplasm, DNA, and a cell membrane