CELLS

CELLS Cells – the basic unit of structure and function in all living things (plants and animals)

First Sighting of Cells No one knew that cells existed until the invention of the microscope. Around 1590, the invention of the microscope allowed us to look at very small objects.

The Microscope A microscope makes small objects look bigger. Some use a lens to focus light. A simple microscope consists of just one lens. Others are compound and use more than one lens.

In 1663, Robert Hooke observed the structure of a thin slice of cork using a compound microscope he had built himself. He was amazed by the millions of cells! Robert Hooke

Anton Van Leeuwehoek At approximately the same time Robert Hooke was looking at cells, Anton Van Leeuwehoek was looking at tiny objects. He was among the first to see single celled organisms. He looked at pond organisms (animacules), teeth scrapings, and many other small objects. With teeth scrapings, Leeuwenhoek was the first person to see single celled organisms called bacteria.

Cell Theory Through the microscope, two German scientist learned that living things are made up of cells. 1838 – Matthais Schleiden concluded that all plants are made of cells. 1839 – Theodor Schwann concluded that all animals are also made up of cells.

Cell Theory Continued Schwann stated: All living things are made up of cells which led to cell theory; All living things are made up of cells. Cells are the basic unit of structure and function in living things. All cells are produced from other cells. Cell theory holds true for all living things.

Light Microscope As time moved on, scientist learned that the microscope needed more than a lens. For a microscope to be useful to a scientist, it must have two important properties: magnification and resolution.

Magnification Magnification is the ability to make things larger than they are. The lens or lenses in a light microscope magnify an object by bending the light that passes through them. A lens with a curved shape is called a convex lens. Because a compound microscope has more than one lens, it can magnify an object even more!

Resolution To create a useful image, a microscope must help you see individual parts clearly. This is called resolution. Good resolution allows you to see fine detail. You need this to look at cells.

Electron Microscopes These use a beam of electrons to examine a specimen. Because electrons are so tiny, they make the resolution much better than a light microscope.

Microscope Timeline