LIFE, ORGANELLES, CELL MEMBRANE, CELLULAR TRANSPORT Cellular Transport (Part II and III) History of the Cell, Microscopes, Types of Cells LIFE, ORGANELLES, CELL MEMBRANE, CELLULAR TRANSPORT

Part 2 Cell Discovery and Theory The link between cell discoveries has been linked through time with advances in microscope technology from the first compound microscope to electron microscopes.

1. History of the Cell A. No one had any clue that cells existed until 1665, when English scientist Robert Hooke made the first compound microscope. He looked at cork, a layer just under the bark of a tree. He saw small box-like structures that reminded him of the dormitories that monks lived in, called cells.

1. History of the Cell B. Inspired by Hooke’s work, Dutch scientist Anton van Leeuwenhoek designed his own microscope in the late 1660s. He started looking at many objects, like pond water and milk, all of which had cells!

1. History of the Cell C. Scientists knew that many items had cells, but no overall theories about them had been made. In 1838, German scientist Matthias Schleiden, after studying as many plants as he could, theorized that all plants were composed of cells.

1. History of the Cell D. A year later Theodore Schwann, after studying as many animal specimens as he could, theorized that all animals were composed of cells.

1. History of the Cell E. In 1885 a Prussian doctor, Rudolph Virchow theorized that all cells are produced from the division of existing cells.

1. History of the Cell F. The Cell Theory was made 1. All living organisms are made of one or more cells. 2. Cells are the basic unit of structure and organization for all living things. 3. Cells arise only from preexisting cells, passing genetic material from parent cells to daughter cells.

2. Microscope Technology - Compound 1. The compound microscope is the type of microscope we use in class. It uses two glass lenses, which multiplies the magnification of the lenses. What is the total magnification if the objective lens reads 10? Multiply the ocular lens (10) x the objective lens (10) for a total of 100.

2. Microscope Technology - Compound 2. The compound microscope is limited, because it uses light to view samples. Light bounces off objects, making them appear blurry past 1000x magnification.

2. Microscope Technology - Electron 1. In the 1940s, the Transmission Electron Microscope (TEM) was invented. It used magnets to aim a beam of electrons towards cells. Samples had to be cut extremely thinly and by dyed with heavy metals. Black and white images were made, magnifying up to 500,000x!

2. Microscope Technology - Electron 2. More recently, the Scanning Electron Microscope (SEM) was invented. Electrons are directed over the surface of the specimen, making a 3-D image. As with TEMs, only non-living specimens could be viewed. Pollen samples

2. Microscope Technology - Electron 3. A Scanning Tunneling Microscope (STM) tunnels electrons through a small probe. 3-D computer images can be made for objects as small as atoms. STMs can be used on living specimens and magnify 2,000,000x!

2. Microscope Technology - Electron Atomic Force Microscopes (AFM) use nanotechnology to actually operate on single cells using a nanoneedle. The needle tip is 200 nanometers (nm) and can enter a cell without damaging the cell membrane.

3. Basic Cell Types Prokaryotic Cells are very small, and have few organelles. They have a cell membrane, but do not have a clearly defined nucleus or other membrane-bound organelles. They have a circular DNA ring called plasmid. Most unicellular organisms, like bacteria, are prokaryotes.

3. Basic Cell Types Eukaryotic cells are over 100x larger than prokaryotic cells, but they are often shown as the same size in pictures for easy comparison. Eukaryotes have many membrane-bound organelles, such as a nucleus. Many have specialized structures, and cells themselves can be specialized and carry out specific tasks, like nerve cells or liver cells.

The prokaryotic cell on the left is smaller and appears less complex than the eukaryotic cell on the right. The prokaryotic cell has been enlarged for the purpose of comparing each cell’s internal structures.

3. Basic Cell Types Origin of Cell Diversity – Scientists theorize that eukaryotes evolved from earlier forms of prokaryotes. The Endosymbiont Theory suggests that a symbiotic relationship between two prokaryotic cells occurred. One cell was larger and offered protection to the smaller cell. The smaller cell was capable of certain tasks like photosynthesis (make sugars) or cellular respiration (harvesting usable energy from sugars).

3. Basic Cell Types The organelles called chloroplasts and mitochondria are similar in size and structure to prokaryotic cells. They also have their own DNA! Your mitochondrial DNA is exactly the same as your mother’s mitochondrial DNA!

Part 3 Cell Structure and Organelles

3. Comparing Cells A. Plant and animal cells are largely composed of the same organelles. B. Cell walls can be in plant cells, prokaryotes, and fungi cells (not animal) C. Centrioles are in animal cells and protist cells (not bacteria or plant)

3. Comparing Cells D. Cilia and flagella can be in protists, prokaryotes and animal cells. E. Lysosomes are in animal cells, but rarely in plant cells. F. Vacuoles are large in plant cells, but are rare and small in animal cells.