1. Aim #10: What are some other tools scientists use in the laboratory?
Date: September 28, 2015
Aim #10: What are some other tools scientists use in the laboratory?
HW:
Complete practice questions- “Tools of Biologist”
Textbook HW #4 (Section 1-3) due Tuesday 9/29
Castle Learning assignment due Wednesday 11:59PM
UNIT 1 TEST- NEXT WEEK THURSDAY/FRIDAY
Do Now: Warm-Up Notebook
Date Title of Activity Page #
9/28 The Microscope 20

2. 1. How do we prepare a wet-mount?
Place drop of water on slide
Place specimen in water
Place cover slip on a 45º angle to avoid air bubbles

3. Microscopy: the use of microscopes to magnify an image for closer observation
Resolution: the clarity of the magnified image
Permits close observation of fine details

4. Image from microscope
(magnification: 100 x)
Image from microscope
(magnification: 45 x)
Image from microscope
(magnification: 10 x)
Lower resolution
Lower resolution
Higher resolution
Higher resolution

5. Microscopes 2. Transmission electron microscope
1. Phase-contrast microscope
Light microscope that enhances contrast
Useful in examining living, unstained cells
3. Scanning electron microscope

6. Phase-contrast Microscope Microscope used for examining living things
Enhances contrast
Does not require staining
Phase Contrast on Right; similar result from staining but doesn’t kill the organism

7. 2. What is an Electron Microscope?
Uses beams of electrons (NOT light waves) to produce magnified image
specially fixed and treated and mounted in a vacuum

8. How do they improve images?
High magnification
High resolution: the ability to separate two objects close together

9. Electron Microscope
Uses a beam of electrons instead of light
Allows for magnifications of >100,000x with high resolution

10. Types of Electron Microscopes
Transmission Electron Microscope (TEM)
Useful for studying interior of cells
Cannot view living specimen
Machine is very delicate and requires special engineers
Machine is very expensive and costs hundreds of thousands of dollars
Scanning Electron Microscope (SEM)
Useful for studying surface of cells
Resulting images have a 3-D appearance
Cannot view living specimen

11. Transmission Electron Microscope (TEM)
Useful for observing cell interiors
Expensive, complex machine converts information about the electrons as they hit the specimen into a visual image.

12. Preparing specimens for TEM requires fixing, dehydrating, and sectioning the specimen using elaborate machinery
Specimen must be cut into very thin tissue
Tissue is killed in preparation

13. 3. What is a stereoscope? AKA: Dissecting Microscope
Binocular: two tubes
Presents a slightly different view of specimen to each eye… 3D
Useful for opaque objects and small organisms or body structures

14. 4. What is a centrifuge? AKA: ultracentrifuge
Separates according to different densities by spinning sample in a test tube at very high speeds

15. Ultracentrifuge
Used for cell fractionation: separation and sorting of cell parts, like organelles
First, tissue is blended and mashed
Produces a liquid called the homogenate
Homogenate is centrifuged to sort the different parts by density

16. Freeze Fracture
Used to study membranes under an electron microscope
Involves freezing and cleaving the membrane into two halves.
Each half is then coated with metal to make a cast which can then be studied under the microscope.

17. 5. Why do we stain cells?
Cell Structures can be made visible by treatment with solutions that color certain parts of cells and not others

18. Living cells are grown in a nutrient-rich medium Ex: agar
Tissue Cultures
Used to study cells in vitro (in a lab) rather than in vivo (in a living thing)
Living cells are grown in a nutrient-rich medium
Ex: agar
Cells will reproduce and scientists can study each generation using tools like a phase-contrast microscope
Find video on HeLa Cells

20. 6. Why do we use indicators?
Substances that change color when in the presence of certain chemicals