{Discovering Cells

Coulter

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

Cells and structure: structures of living things are determined by the amazing variety of ways in which cells are put together. (tree/dog)

Cells and function: the processes that enable it to stay alive and reproduce.

Many and small: human skin cells, one square centimeter of your skin’s surface contains more than 100,000 cells.

An overview of cells

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

Microscope-is an instrument that makes small objects look larger.

Some do this by using lenses (like eye glasses) to focus light.

Simple microscope- one lens Complex microscope- more than one lens

First Observation of Cells

1663 Hooke used his microscope to observe the structure of a thin slice of cork

He thought what he saw looked like small rooms, so he called them cells.

He described what he observed; “these pores, or cells, were not very deep, but consisted of a great many little boxes…”

He was amazed about how many cells there were, he estimated that in 1 cubic centimeter there were 1,200,000,000 cells “almost incredible”

Robert Hooke

Looked at drops of lake water, scrapings from teeth and gums, and water from rain gutters.

Was surprised to find a variety of one-celled organisms.

Noted that many moved, he called them animalcules (little animals)

Anton van Leeuwenhoek

Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.

In 1839, Schleiden concluded that all plants are made of cells.

In 1840, Schwann concluded that all animals are also made up of cells

This huge discover did not explain where cells came from.

In 1855, Virchow proposed new cells formed only from cells that already exist.

Development of the cell theory

Is a widely accepted explanation of the relationship between cells and living things

All living things are composed of cells

Cells are the basic units of structure and function in living things

All cells are produced from other cells

The Cell Theory

The lenses in light microscopes magnify an object by bending the light that passes through them.

Observe a hand lens What do you notice? Lens is curved, thicker in the middle. A lens

with this curved shape is called a convex lens.

Light passes through the sides and the lens bends inward. When this light hits the eye, the eye sees the object as larger than it really is.

Magnification of Lenses

Uses more than one lens. Total magnification of the lens is equal to

two lenses multiplied together. Example: first lens makes object 10

times larger. The second lens makes the object 40 times larger.

10x40=400

Compound microscope

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

sharpness, of an image

Resolution

Electron microscopes use a beam of electrons instead of light to produce a magnified image.

Electrons are tiny particles that are smaller than atoms.

Can see smaller images than those of light microscopes.

Resolution is much better than light microscopes.

Electron microscope

Problem: How can you build a compound microscope?

Materials: 2 dual magnifying glasses, each with one

high-power and one low-power lens Metric ruler Black construction paper tape

Build a microscope

Work with a partner. Using only you eyes, examine words in a book. Then use the high-power lens to examine the same words. In your notebook write your observations.

Hold the high-power lens about 5 to 6 cm above the words in the book. When you look at the words through the lens, they will look blurry.

Keep the high-power lens about 5-6cm above the words. Hold the low-power lens above the high-power lens. Write your observations.

Move the low-power lens up and down until the image is in focus and upside down.

Build a microscope

One the image is in focus, experiment with raising and lowering both lenses. Your goal is to produce the highest magnification while keeping the image in clear focus.

When the image is in focus at the position of highest magnification, have your lab partner measure and record the distance between the book and the high-power lens. Your lab partner should also measure and record the distance between the two lenses.

Write a description of how the magnified words viewed through two lenses compares with the words seen without magnification.

Build a microscope

Based on what you learned in part 1, work with a partner to build your own microscope.

Sketch your design in lab report. Test your microscope by examining a

chosen living and non-living organism from outside. Write down observations. Draw to the best of your ability what you see.

Build a microscope