1. Friday, 09/29/17 Do Now: What is that?
Magnified Image:
What is that?
Make a qualitative observation of the magnified image.
Describe what you see.
Infer its identity.

2. Cork Cells under a Microscope
Magnified Image:

3. Chapter 7: Cell Structure & Functions
7.1 Life is Cellular notes
-Smallest living unit of any organism = CELL!

4. The Discovery of the Cell:
-“SEEING is believing”
-Without INSTRUMENTS to make cells visible, they remained undiscovered...
-Discovery of cells was made possible by the invention of the  MICROSCOPE.

5. Early Microscopes: But first, some history…
Late 1500s, European eyeglass makers discovered that combining many glass lenses could MAGNIFY small objects  inspiring the first microscopes to be made.

6. In 1665, ROBERT HOOKE used an early COMPOUND microscope to look at a non-living thin slice of CORK (a plant material).
Cork was viewed under the microscope and described as thousands of tiny “empty chambers” in monasteries, which ROBERT HOOKE called CELLS.

7. Around same time as Robert Hooke, ANTON VAN LEEUWENHOEK used a SINGLE-LENS MICROSCOPE to observe pond water.
Pond water was observed to be full of tiny living ORGANISMS.
Human mouth was observed to full of (what Biologists would later call)  BACTERIA.
Anton van Leeuwenhoek was the first to observe living MICROORGANISMS using a simple microscope.

8. The Cell Theory:
(Recall) Theory: A well-tested explanation bringing together OBSERVATIONS and hypotheses to explain a phenomena.
Observations made by scientists confirm that cells are the basic UNITS of LIFE..
German botanist Matthias Schleiden: all PLANTS are made of cells.
German biologist Theodor Schwann: all ANIMALS are made of cells.
German physician Rudolf Virchow concludes: NEW cells can be produced only from division of EXISTING cells.

9. *All these discoveries brought together to form the → Cell Theory*
1- All living things are made up of cells
2- Cells are the basic units of structure and function in living things
3- New cells are produced from existing cells.
*Recall*  8 Characteristics of Living Things:
1-Universal Genetic Code (DNA)
2-Grow & Develop
3-Respond to their Environment
4-Made up Cells
5-Reproduce
6-Maintain a Stable Internal Environment (Homeostasis)
7-Obtain & Use Material & Energy
8-Evolve

10. Exploring the Cell Using a Microscope:
Microscope: enlarges (magnifies) the image of something very SMALL.
Most microscopes use LENSES to magnify the image by focusing LIGHT or ELECTRONS.

11. 2 Types of Microscopes:
Compound Light Microscope: The magnification of an image when LIGHT passes through 2 lenses.

12. Limitations of Compound Light Microscope
Limitation #1: LIGHT limits detail of images because light is diffracted (scattered) as it passes through matter, so can only produce clear images to a magnification of about 1000x.
Limitation #2: most living cells are TRANSPARENT.
Solution: Use chemical STAINS or DYES.
(Some dyes/stains are so specific that they only reveal certain compounds or structures within the cell.)
Onion Cells Stained with Methylene Blue

13. 2. Electron Microscope: shoots a beam of ELECTRONS at a subject in order to produce a super magnified image.
2 major types of electron microscopes:
TRANSMISSION electron microscope: magnify cell structures and large protein molecules.
Beams of electrons can only pass through thin samples, so cells and tissues are cut into very thin slices → images appear: FLAT and 2-dimensional.

14. 2. SCANNING electron microscope: pencil-like beam of electrons is scanned over SURFACE of specimen.
Image is formed at specimen's surface, so samples do not have to be cut into thin slices to be observed → images appear: 3-dimensional images of the specimens' SURFACE.

15. Cells come in a variety of SHAPES and SIZES.

16. Prokaryotes vs. Eukaryotes:
All cells:
Contain DNA.
DNA: molecule that carries biological INFORMATION.
2. Surrounded by a thin flexible layer called: CELL MEMBRANE

17. Prokaryotes vs. Eukaryotes:
Cells are categorized into 2 groups based on whether a NUCLEUS is present or not:
Nucleus (plural: Nuclei): large-membrane enclosed structure containing genetic material in the form of DNA AND CONTROLS many of the cell’s activities.
EUKARYOTES: Cells that enclose DNA in their nuclei.
PROKARYOTES: Cells that do not contain DNA in their nuclei.
Eukaryote
Prokaryote

18. Prokaryotes vs. Eukaryotes:
Smaller
Simpler
Do not separate genetic material within a nucleus.
Ex: BACTERIA
2. Eukaryotes:
Larger
More complex: many structures and internal membranes,
highly specialized
Separate genetic material from the rest of the cell.
Ex: UNICELLULAR: Protists
Ex: MULTICELLULAR: Plants, animals, fungi.
Eukaryote
Prokaryote

20. A. K. B. C. J. D. I. E. F. H. G.

21. Calculating Magnification:
Ocular Lens (10x)
OCULAR lens, 10x, magnifies the image.
OBJECTIVE lenses, magnifies the image even more: 4x, 10x, or 40x.
Total magnification = Ocular magnification x Objective magnification

22. How to use a microscope to see small things: https://www. youtube
1- Wet Mount: Prepared using water & coverslip

23. 2- Field of View: What is seen through the microscope.

24. 3- Depth of Field: Referring to layers, 3-D image using fine adjustment in high power.

25. Video Demonstration

26. What was the difference between your observation of the Elodea plant under the 10x objective versus the 40x objective lens?
Let’s Calculate the total magnification in each:
Formula: ocular lens magnification power * objective lens magnification power.
Ocular Lens: 10x
Objective lens: 10x or 40x
10x multiplied by 40x = 400x
What does this imply about the difference between the images under each magnification lens?
The higher the magnification, the more magnified the image will be.