1. Microscopes provide windows to the world of the cell

2. Cellular Diversity The average adult has nearly 100 trillion cells
There are about 200 different types of cells
Cells come in a variety of shapes and sizes
Cellular diversity permits organization of cells into more complex tissues and organs 2

3. History of the Microscope
1665, Robert Hooke described cells using a light microscope
Magnification vs resolution
Highest magnification of l.m. = 1000x
1950, Electron microscope allowed researchers to clearly identify organelles
There are 2 types:
Transmission
Scanning

4. Transmission Electron Microscope (TEM)
e- transmitted through specimen are focused
image magnified by electromagnetic lenses to bend trajectories of charged e-
Used to study internal cell structure
Image is focused onto a viewing screen/film

6. Scanning Electron Microscope (SEM)
e- beam scans surface of specimen that is coated with a thin film of gold
Beam excites secondary e- on sample’s surface
Secondary e- are collected & focused on viewing screen
Useful for studying surface of specimen
SEM has great depth of field & produces 3D image

7. SEM images

8. Disadvantages of Electron microscopes
Can usually only view dead cells because of the elaborate preparation required
May introduce structural artifacts

9. Cell Fractionation
Technique that enables researchers to isolate organelles without destroying their function
Disrupted cells are centrifuged to isolate components of different sizes, densities, and shapes

10. Surface area: volume ratio
Why do you cut up potatoes to boil them?
Place in order depending on which will dissolve fastest  slowest
granulated sugar
Powdered sugar
Sugar cube
Fine sugar

11. Cells Prokaryotic vs Eukaryotic Cell sizes (0.1-100um)
What limits a cell from being too large?
Too small?
Eukaryotic cells have 1000x volume of prokaryotic cells, but only 100x the surface area. How can they compensate for the small surface area to volume ratio?

12. Prokaryote
“before nucleus”
Eukaryote
“true nucleus”

13. A Generalized Cell
Cytoplasm - all the cellular contents between the plasma membrane and the nucleus - cytosol - the fluid portion, mostly water *site of many chem. Rx. - organelles - subcellular structures having characteristic shapes and specific functions 13

14. The cytoskeleton - network of protein filaments throughout the cytosol -provides structural support for the cell -three types according to increasing size: microfilaments (cables), intermediate filaments (cables), and microtubules (support beams)
Resist
tension
Bearing
tension
Resist
compression 14

16. Organelles
Centrosome - located near the nucleus, consists of two centrioles 16

17. Cilia and Flagella
Cilia - short, hair-like projections from the cell surface, move fluids along a cell surface
Flagella - longer than cilia, move an entire cell; ex. sperm cell’s tail 17

18. Internal Membranes Partitions cell into compartments
Have unique lipid & protein compositions depending upon their specific fx.
Participate in metabolic reactions (enzymes)

19. Class I: membrane derived
1. Nuclear envelope - a double membrane that separates the nucleus from the cytoplasm
Nuclear pores - numerous openings in the nuclear envelope, control movement of substances between nucleus and cytoplasm
Nucleolus - spherical body that produces ribosomes 19

20. 2. Endoplasmic reticulum - network of membranes in the shape of flattened sacs or tubules
- Rough ER - connected to the nuclear envelope, a series of flattened sacs, surface is studded with ribosomes, produces various proteins
-Smooth ER - a network of membrane tubules, does not have ribosomes, synthesizes fatty acids and steroids, detoxifies certain drugs

21. 3. Golgi complex - consists of 3-20 flattened, membranous sacs called cisternae
- modify, sort, and package proteins for transport to different destinations
- proteins are transported by various vesicles

22. 4. Vesicles Sacs made of membrane
Transport substances throughout cell and to/fro membrane

23. 5. Vacuoles
Food vacuole  formed by phagocytosis (protists & macrophages)
Contractile vacuole  pumps excess water from cell (protozoans)
Central vacuole  enclosed by membrane (tonoplast); stores organic compounds, ions, poisons, provides turgor pressure (plants)

24. 6. Lysosomes Sequesters destructive enzymes from cytosol
Maintains optimum acidic environment for enzyme function

25. Peroxisome Bound by a single membrane derived from lipids w/i cell
Contains enzymes that transfer Hydrogen atoms from various substrates to oxygen (H2O2).
Contains catalase that converts H2O2 to water.
Breaks down fatty acids
Detoxification of alcohol & other poisons (liver)

26. Mitochondria - the “powerhouses” of the cell
Class II: bacteria like organelles
(energy production)
Mitochondria - the “powerhouses” of the cell
Generate ATP
More prevalent in physiologically active cells: muscles, liver and kidneys
Inner and outer mitochondrial membranes
Cristae - the series of folds of the inner membrane
Matrix - the large central fluid-filled cavity
Self-replicate during times of increased cellular demand or before cell division

27. Class III: Involved in Gene Expression