Cells and Cell Theory Chapter 1

Cells??? Cells were discovered in 1655 by Robert Hooke From the study of different organisms, a cell theory was developed. This theory has the following parts: 1. All living things are made up of cells 2. Cells are the basic structural and functional units of life 3. All cells arise from the division of other cells

Are All Cells Alike? All cells can be broken into 2 basic categories Prokaryotic No nuclear envelope surrounding its chromosomes (i.e. no true nucleus) I.e. Bacteria Eukaryotic Cells with a true nucleus surrounded by a nuclear envelope i.e. Plant cells, Animal cells

So what???? Scientists have modified cells so that they produce chemicals called antibodies that fight diseases such as cancer, leprosy, and tetanus (lockjaw). Artificial skin – incubated in petri dishes Change cells from one type to another – skin cells to bone cells, fat cells into nerve cells (osteoporosis and Parkinson’s disease) Use cells for routine tests to determine presence or type of disease

. . . and what? the human body is made up of about 100 000 000 000 000 specialized cells a colony of prokaryotic, mutualistic bacteria live in our gut countless cells enter our bodies as pollen, spores, eggs, and protists our skin supports several fungal species and Staphylococcus epidermis many types of cells are put to use by humans (i.e. yogurt bacteria) and some others are pathogens all cells must incorporate nutrients, excrete wastes, metabolize, and reproduce

Botany + Zoology = Biology 1665 – Robert Hooke - observed compartments in cork that reminded him of honeycomb cells (= rooms) 1674 – Leeuwenhoek - first to see what are now called microorganisms (bacteria, yeast, algae, protists) in a drop of water 1820 – Robert Brown - discovered the nucleus in plant cells 1838 - Matthew Schleiden - found cells in all plants he examined (botanist)  Theodor Schwann - found cells in all animal parts he (zoologist) examined    marriage of botany and zoology into biology, the study of all life 

Observing Cells Compound Light Microscope: objective lens close to the specimen and an ocular lens close to the eye magnification is the product of the objective and ocular lens and represents the ability of a microscope to enlarge the image i.e. 10x ocular lens and 10x objective lens = specimen 100x larger resolution is a measure of how well close objects can be seen as separate, determined by the light source, and represents the quality of the image (best resolution for light microscopes is about 200 nm (2 x 10-7 m) Can observe live specimens

TEM Transmission Electron Microscope (TEM)  electrons pass through a thin section, encased in plastic (developed at U of T in 1937) magnifies up to 5 000 000X, resolution up to 0.2 nm Only observes dead cells TEM

SEM Scanning Electron Microscope (SEM) use magnets to reflect electrons from surface of a specimen, producing a 3D image  magnifies up to 300 000X, resolution up to 10 nm