1. AP Bio Chapter 4

2. Microscopy Three important aspects: Light microscope (LM) –
Magnification – how large the object appears compared to actual size
Resolution – how clear the image appear; how well two points can be distinguished
Contrast – visible differences in parts of the sample
Light microscope (LM) –
Visible light passes through the specimen and then through glass lenses
Lenses refract light and magnify the image
Highest magnification ~ 1000 x
Living cells can be observed
Subcellular organelles are generally too small for accurate resolution
Stains are used to enhance the contrast
These microscopes are used in most high school and college biology courses

3. Microscopy…
Electron microscope (EM) – use a beam of electrons; two types:
Scanning electron microscope (SEM)
Focuses the electrons on the surface of the specimen; image appears ‘3-D’
Transmission electron microscope (TEM)
The beam of electrons goes through the specimen, allowing the internal study of cells
A specimen must be treated with a thin layer of metal (usually gold) and then placed in a vacuum chamber before being observed
Information is sent to a computer which then projects the image on its screen
Living organisms cannot be observed
For these reasons as well as cost and practicality these microscopes are not used in high school biology courses

4. Cell parts ALL cells have these basic features:
Plasma membrane
Semifluid substance called cytosol
Chromosomes (carry genes)
Ribosomes (make proteins)
Prokaryotic cells – no internal membrane system
Bacteria and Archaea
Eukaryotic cells – internal membrane system
Protists, fungi, plants, animals
Separates different areas of the cell for different jobs

5. Eukaryotic cells
Metabolic requirements set upper limits on the size of cells
The ratio of surface area to volume of a cell is critical
Small cells have a greater surface area relative to volume

6. Cellular organelles
Describe the structure and function of the following:
Lysosomes
Vacuoles
Nucleus
Mitochondria
Nuclear envelope
Chloroplasts
Nucleolus
Cytoskeleton
Ribosomes
Cilia and flagella
Rough endoplasmic reticulum
Cell walls
Smooth endoplasmic reticulum
Cell junctions
Golgi apparatus