Discovering CellsLesson 1 – TB pages 122-129

What are cells?

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

• All living things are made of cells.

Cells and Structure

• When you describe what an object is made of and how its parts are put together, then you are describing the structure of an object.

• When you describe what a living thing is made of and how its cells are put together, then you are describing the structure of a living thing.

Cells and Function

• An organism’s functions are the processes that enable it to live, grow, and reproduce.

• Cells are involved in all functions of the organism. They work together.

• Each cell carries out the basic functions that let it live, grow, and reproduce. Those functions include obtaining oxygen, food, and water and getting rid of wastes.

What Scientists made key discoveries in the early study of cells?

Robert Hooke

• In 1663, he observed a slice of cork with his microscope and discovered cells. He called them “small rooms.”

Anton van Leeuwenhoek• Around 1674, he discovered one-

celled organisms with his microscope. He called them “animalcules.”

Matthias Schleiden

• In 1838, he concluded that all plants are made of cells.

Theodor Schwann

• 1n 1839, he concluded that all animals are made of cells.

• He discovered the differences between animal and plant cells.

Rudolph Virchow

• In 1855, he proposed that new cells are formed only from cells that already exist.

The Cell Theory

How many years did it take for the cell theory to unfold? Why did it take so long?Why is it a scientific theory and not a scientific law?

Light Microscopes• focus light through lenses to produce a

magnified image

Compound Microscope

• focuses light through a lens to produce an image• magnifies the image using two lenses at once• can magnify an object more than a single lens can

• This compound microscope has a 10x lens in the eyepiece. The revolving nosepiece holds three differentLenses: 4x, 10x, and 40x.

Calculate the three total magnification possible for the microscope.10 x 4= 40x10 x 10 = 100x10 x 40 = 400x

Electron Microscopes• use beams of electrons

instead of light• can see objects that are

too small to be seen with light microscopes

• Have higher magnification and better resolution