1. Microscope Notes “Looking at Cells”
Cells were discovered in the 17th century, when microscopes were invented….

2. Cells were discovered by…..
Robert Hooke, in 1665 he looked at a thin piece of cork and ‘saw a lot of little boxes’ which reminded him of the small rooms where monks live, so he called them cells
Anton von Leeuwenhoek used a microscope ten years later to view water from a pond, and he called the tiny organisms he saw ‘animalcules’

3. Measurement
Cells are measured in units of micrometers, abbreviated μm. The symbol μ stands for the prefix ‘micro’
One millimeter = one thousand micrometers!
1mm = 1000 μm
Or, 1 μm = mm

4. Know these words…..
Magnification: the amount of times a specimen being viewed is enlarged in order to be seen, varies with power of microscope
Resolution: the ability that the microscope has to distinguish between two different objects, ie. The nucleus vs. the endoplasmic reticulum
Contrast: ability to see detail within the specimen clearly

5. Types of microscopes Light microscope
Transmission and scanning electron microscopes
Scanning tunneling microscope

6. Compound light microscopes
What we work with in class
Light rays pass through specimen and come into focus through two glass lenses.
The eyepiece lens magnifies a total of 10x.
The objective lens varies with microscopes but can be up to 100x magnification.
Eyepiece lens X objective lens = Total magnification

7. Transmission Electron Microscopes
Use electrons to pass through specimens to view detail
image projected onto screen or photographic film

8. Scanning electron microscopes
The specimen is first coated with a thin layer of metal.
An image is produced by the electrons which bounce off of the specimen.

9. Scanning tunneling microscopes
New video & computer techniques increase microscope resolution and magnification
Uses a needle-like probe to measure voltages of electrons.
It can track the movement of electrons and can see atoms!

10. Compare the images produced by different microscopes…..

11. Compound Light Microscope
An image of sperm

12. Transmission Electron Microscope
a technique where a beam of electrons is passes through & interacts with an ultra thin specimen,
An image is formed, magnified and focused onto an imaging device, such as a fluorescent screen, on film, or detected by a sensor with a camera.

13. Scanning Electron Microscope
S.E.M. image of sperm
Fly specimen prepared for scanning.

14. Scanning Tunneling Electron Microscope
a powerful instrument for imaging surfaces at the atomic level
This is a nanotube of carbon atoms in what is called a “pea-pod” arrangement.

15. Cell Features
The cell theory: was built on the ideas of Hooke and Leeuwenhooek by the following:
Schleiden who said that cells make up every part of a plant
Schwann who claimed that animals are also made of cells
Virchow who determined that cells come from other cells.

16. The cell theory summarized…
All living things are made of one or more cells
Cells are the basic unit of structure and function in organisms
All cells arise from existing cells

17. Cell size and sufrace area:volume ratio
Small cells function more efficiently than larger cells
If the surface area of a cell is larger than it’s volume, then the cell can gather essential nutrients and water and they can get in fast.
If the surface area to volume ratio is close in number to the volume, it takes too long for materials to reach the interior of the cell

18. Common features of cells:
Most cells have…
A cell membrane: encloses cell, separates interior
Cytoplasm: the fluid in which interior cell structures are suspended, also called cytosol
Cytoskeleton: for cellular structure
Ribosomes: to make proteins
DNA: all cells have DNA which contains instructions for making proteins, regulating the activities of the cell, and allowing the cell to reproduce. Red blood cells lose their DNA at a certain point in their life.

19. Prokaryotes
A single-celled organism that lacks a nucleus and other internal compartments
Common prokaryotes which cause infection and spoil food: Bacteria

20. Characteristics of Prokaryotes:
Have little internal structure
Many have a capsule and flagella
DNA is located near the center of the cell and is not contained in a nucleus
A cell wall surrounds the membrane and provides structure and support
Many have flagella which propel them along

21. Typical prokaryote:

22. Eukaryotic Cells Cells with a nucleus and other organelles
An organelle is a structure within a cell that carries out specific activities for that cell
Some eukaryotic cells have cilia which are short hair-like structures that protrude from the surface of the cells

23. cytoskeleton
Provides the internal framework of an animal cell, much as our skeleton provides the internal framework of our bodies
Three types of cytoskeleton fibers:
Actin fibers: found just inside of the cell membrane; helps cell membrane move
Microtubules: transport information from nucleus to different parts of the cell
Intermediate fibers: keep ribosomes and enzymes in place within cell

24. The cell membrane
to separate the internal from external environment of the cell
Regulates materials entering and leaving the cell.
Helps the cell, in turn the organism, maintain homeostasis

25. cell membrane structure
Made up of a phospholipid bilayer
Phospholipid: a molecule with a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail

26. Cell membrane proteins
Proteins embedded in the membrane have polar and nonpolar ends just like the membrane; this keeps them embedded inside of the membrane
These proteins have different functions:
Receptor proteins recognize and bind to substances outside the cell
Enzymes assist chemical reactions in the cell
Transport proteins help substances move across the membrane