Download Intro to Cells / Microscopes

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
• 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
Exploring the Cell
• 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
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