Chapter 7.1 Life Is Cellular

The Discovery of the Cell In 1665 Robert Hooke used a very basic compound microscope to look at living things. He saw boxes in cork (dead plant material) and named them cells. Anton van Leeuwenhoek discovered little tiny animals in pond water. They were the first people to see cells.

The Cell Theory Cells are the basic unit of life. Matthias Schleiden came up with the idea that all plants were made of cells. Theodor Schwann said that all animals were made of cells. Rudolf Virchow said that new cell could only be made from the division of existing cells. All these discoveries let to the cell theory: All living things are made of cells. Cells are the basic unit of structure and function in living things. New cells are produced from existing cells.

Exploring the Cell Today researchers are able to use fluorescent labels and light microscopy to follow molecules around cells. They can scan cells with a laser and build a 3D image. Video technology can produce movies of cells growing, dividing, and developing.

Electron Microscopes Electron microscopes can magnify up to 1000 times. Transmission electrons microscopes beam electrons and allow a cross- section view of cells and tissues. Scanning electron microscopes bounce electrons on the outer surface of a specimen so it gives a 3D image of cells. Electron microscopes can only show dead specimens.

Scanning Probe Microscopes These microscopes produce images by tracing the surface of samples with a fine probe. They can even see a single atom.

Prokaryotes and Eukaryotes All cells have a cell membrane (a barrier around the cell). And they contain DNA. There are 2 categories of cells: prokaryotes and eukaryotes. Eukaryotes have a nucleus (large membrane bound structure that contains DNA and controls cell activities). Prokaryotes do NOT have a nucleus.

Prokaryotes These cells are smaller and simpler than eukaryotic cells. They have genetic material (DNA) but not in a nucleus. Prokaryotes are still able to grow, reproduce, and respond to their environment, and move. These are bacterial cells

Eukaryotes These cells are larger and more complex than prokaryotes. They are highly specialized meaning they have membrane bound structures in them. They have a nucleus that contains their DNA. Some eukaryotes are single celled organisms, some are large, multicellular organisms. Plants, animals, fungi, and protists are all eukaryotes.