Early beginnings Robert Hooke - described “cells” Leuwenhoek - described microbes Leuwenhoek - published first drawings of bacteria from the mouth

“Cell theory” 19th century Schlieden (botanist) & Schwann (zoologist) Cell Theory –organisms composed of one or more cells –the cell is the smallest unit of life –continuity of life is from the growth and division of cells

Basic cell Common features of prokaryotic and eucaryotic cells –Plasma membrane –DNA –Cytoplasm

Prokaryotes Pro - “before” & karyote - “nucleus” –no nucleus plasma membrane cell wall capsule flagella pili

Eucaryotes Eu - “true” & caryote - “nucleus” –contain a nuclear membrane bound nucleus plasma membrane cytosol cytomembrane system –Endoplasmic reticulum –Golgi bodies –Vesicles

Plasma membrane Barrier between the outside world and the inside world of the cell composed of phospholipids arranged in a bilayer (see Figure 11.11) Selectively permeable

Cytoskeleton Figure 1.20 Structure –Actin, intermediate filaments, microtubules –Protein Function –Structural integrity –Organization –Motility

Mitochondria Figure 1.11 “Cellular Power Plant” Structure –Double membrane -outer membrane & inner membrane Function –Oxidize food to produce ATP –Site of aerobic respiration

Chloroplast Figure 1.13 Structure –double membrane - outer membrane & thylakoid membrane Function –Site of photosynthesis

Central Vacuole Plants only Structure –Membrane bound Function –Storeage

Summary Nucleus - localize chromosomes ER –sER - synthesize lipid –rER - assemble polypeptides Golgi bodies - modify and transport protein and lipids Vesicles - transport Mitochondrion - synthesize ATP

Non - membranous structures Ribosomes - assemble polypeptides Cytoskeleton –Structural –Organizational –Motility

Light microscope Brightfield microscopy –illumination source - light –resolution proportional to 1/2 wavelength –practical resolution > 500nm –usually requires some type of staining –see Panel 1.1

Brightfield microscopy Variations –Darkfield object appears bright on a dark background –Phase contrast can view organelles without staining –see Panel 1.1

Fluorescent microscope Source of illumination - UV light or short wave visible wavelengths Requires a fluorochrome stain Excitation wavelength - UV Emission wavelength - longer wavelength –usually in visible light range See Panel 1.1

Electron microscope Source of illumination - electron beam Types of electron microscopes –transmission - TEM resolution 2nm see Panel 1.1 –scanning - SEM resolution 3-20nm See Panel 1.1

Newer microscopes Confocal microscope –uses laser light to “virtually” dissect specimen Atomic Force Microscope –Extremely high resolution –can view living organisms –Website hapter3/Chapter3.html hapter3/Chapter3.html

Cell size Small spheres have a greater surface area to volume ratio (SA:V) than large spheres Surface area to volume ratio influences exchange of nutrients and waste products from a cell. The smaller the SA:V, the greater the rate of exchange!