CH-1 SEC-1Discovering Cells &

Microscopes

An Overview of Cells

• Cells are the basic unit of structure and function in living things.

• This means that cells make up the parts of an organism and carry out all of an organisms processes or jobs.

The Cell Theory

• The cell is the basic unit of structure and function in all living things.

• All living things are made up of cells.

• Cells come from pre-existing cells.

Exceptions to the Cell TheoryThese are facts that can not be explained by the Cell Theory.

• Viruses are not made up of cells, but they do contain genetic material DNA.

• The first cell could not have arisen from a previously existing cell, scientists don’t know the origin of the first cell.

History of Cell Study

• Scientists did not know much about cells until the discovery of the microscope.

• Zacharias & Hans Janssen- Dutch eyeglass makers (1590). Developed the first compound microscope.

History of Cell Study• Robert Hooke- English (1660’s) developed a

compound microscope and observed thin slices of cork (cell walls). He came up with the term ”cell”.

History of Cell Study• Anton van Leeuwenhoek- (1674) also built

microscopes, and viewed pond water. He saw tiny one-celled organisms which he called animalcules.

History cont…..• Matthias Schleiden- (German, 1838) botanist,

concluded that all plants were made up of cells.• Theodor Schwann- (German, 1839) zoologist,

studied animal cells, concluded that all animals were made up of cells.

• Rudolf Virchow- (1858) concluded that all new cells must come from previously existing cells.

First Observations of Cells

• The invention of the microscope made it possible for people to discover and learn about cells.

• A microscope is an instrument that makes small objects look larger.

Microscopes

• Microscopes are used to study materials that can’t be seen with the unaided or naked eye.

• A simple microscope contains only one lens.• A compound microscope uses two lens to

increase the size of a specimen.• A specimen must be thin enough for light to

pass through it.

Simple Microscopes Compound Light Microscope

Magnification• Magnification is the ability to make things

look larger than they are. • The lens in light microscopes

magnify an object by bending the light that passes through them.

• When this light hits the eye, the eye will see the object much larger than it really is.

Total Magnification• The total magnification of an object is found by multiplying the

magnification of the

objective lens x eyepiece lens• Lets practice… The microscopes we use in class have an

eyepiece lens that is 10x.

Each objective is; scanning 4xlow power 10xhigh power 40x

Resolution

• The ability to clearly distinguish the individual parts of an object is called resolution.

• It’s also another term for the “sharpness” of an image.

Plant Cells

Electron Microscopes

• Use a beam of electrons instead of light to produce a magnified image.

• Electrons are VERY tiny particles that are even smaller than atoms.

• This type of microscope is used to view EXTREMELY

small objects.

Electron Microscope

Electron Microscope Images

Lets Practice•

Use the following information to answer the question; eyepiece 10xscanning 4x

low power 10xhigh power 40x

• What is the total magnification when you view a specimen on low power?A. 10xB. 40x

C. 100x D. 400x

Parts of the Microscope

NOW you’re going to label your diagram of the microscope

9. Eyepiece 10x (ocular)

1. Body Tube

2. Revolving Nosepiece

10. Arm3. Scanning Objective 4x4. Low Power Objective 10x5. High Power Objective 40x

11. Stage6. Stage Clips

12. Coarse Focus Knob

13. Fine Focus Knob

14. Base

7. Diaphragm8. Light