Cell Theory & Eukaryotic Structures

• Cellular timeline– 1665… Robert Hooke views cork under a microscope and

describes tiny chambers he calls cells– 1674… Anton van Leeuwehoek observes single celled organisms

in pond water using a microscope– 1838… Matthias Schleiden states that all plants are made of cells– 1839… Theodor Schwann states that all animals are made of cells– 1855… Rudolph Virchow… establishes the cell theory

• Cell theory– All living things are made of cells – Cells are the basic unit of life – New cells come from existing cells

Exploring the Cell• Study called cytology

– Light microscopy - a device using light and mirrors to magnify an object. Its resolution (measure of clarity) is limited to 0.2 mm. • good for seeing the gross structure of

most cells and bacteria • most appropriate for viewing live

specimens – Electron Microscopy - a device that

concentrates a beam of electrons onto a plated surface. Its resolution is to around 2nm. (good for seeing organelles and some macromolecules)• (SEM) scanning electron microscope -

good for detailed investigation of surface structure

• (TEM) transmission electron microscope - good for seeing internal structures of cells

– Cell fractionation • uses a centrifuge to separate the parts of

the cell by mass

Prokaryote vs Eukaryote• Prokaryotes - no true nucleus

– DNA is not separated from the rest of the cell (no nuclear membrane) but is concentrated in a nucleoid region

• Eukaryote - true nucleus – DNA is located in a membrane bound

compartment called the nucleus • The nucleus houses the genetic information of the

cells. It is responsible for directing protein synthesis which effects every function of the cell.

– area between the nucleus and the plasma membrane is called the cytoplasm • contains the membrane bound

organelles

Prokaryote vs Eukaryote

• Common features – plasma membrane - all cells are bound by a plasma membrane

• functions as a selective barrier - hydrophobic interior with hydrophilic exterior which is embedded with channel proteins used to transport materials.

• has a very large surface to volume ration in order to efficiently transfer gases, nutrients, & waste in and out of the cell

Prokaryote vs Eukaryote• Prokaryote (Bacteria)– The cell performs everything required for survival

• Growth• Reproduction• Response to environment• Movement

• Eukaryote (Protists, Fungi, Plants, Animals)– Larger and more complex than prakaryotes– Single celled (protists) or multicelled

• Cells may highly specialized to carry out specific functions