1. People have been studying cells for the last 300 years. Discoveries made have only been possible with the development of new technologies. One of which came in the form of improved microscopic design.

2. In the mid 1600s, Anton van Leewenhoek created the first microscope.
   1. Robert Hooke discovered cells. When observing cork with a simple microscope, he named the tiny rectangular boxes he saw, CELLS.

3. In the next 200 years, higher quality lenses were developed improving magnification and clarity.
   1. In 1838, Matthias Scheiden after studying plant structure concluded that all plants are composed of cells.
   2. In 1839, Theodor Schwann found that animal tissue looked similar to plant tissue; therefore concluded it too was also made up of cells.
   3. Some years later Robert Brown discovered an object near the center of many cells, now called the nucleus.
   4. In 1858, Rudolf Virchow stated that all cells come from other living cells.

   5. All of the above scientists helped create what is called the
      CELL THEORY:
      1. All living things are made up of cells.
      2. Cells are the smallest working units of living things.
      3. All cells come from other living cells.

         THE CELL THEORY APPLIES TO ALL ORGANISMS!!!

4. By the end of the 1800s, most cell organelles had been discovered and studied. In the mid 1900s, several advanced microscopes were developed providing a more detailed view of cells.
   1. The Compound Light Microscope is the type we use in class. It contains several lenses lined up with each other allowing it to magnify objects up to 1000 times.

   2. The Electron Microscope uses a beam of electrons instead of light. It can magnify up to 1,000 times larger than a compound light microscope.
      There are two types of electron microscopes:
      
      1. A Transmission Electron Microscope (TEM) shines beams of electrons through a sample, and then captures the image on a fluorescent screen. (The shadow of the object is seen.) Sample must be sliced very thin so the beam can pass through them.
      2. A Scanning Electron Microscope (SEM) shines a beam of electrons on the surface of the sample. The reflected electrons are captured and are used to form an image on a television screen.

   3. The Scanning Probe Microscope traces the surface of a sample with a tiny tip known as a probe.

1. Three Main Parts of the Cell (1.) Plasma Membrane, (2.) Cytoplasm, and (3.) Nucleus)
   1. The plasma membrane (or cell membrane) is a flexible, protective layer that separates the cell from its environment.
      1. The membrane is often referred to as a selectively permeable membrane, meaning it protects itself by letting only certain substances through it.

   2. The cytoplasm is a jelly-like fluid that fills the cell. It contains water, food, building materials, and organelles. (cyto-- cell, plasm�fluid)

   3. The nucleus controls all activities of the cell. There are two main categories of cells divided simply by the presence or absence of a nucleus:
      1. Prokaryotes - �pro- before, karyote- nucleus� do not have a nucleus. Their DNA floats around the cell without protection.
         Bacteria are the most important example of prokaryotes. They contain:
         1. Cell Wall (made up of protein-polysaccharide)
         2. Plasma membrane
         3. 1 ring-like chromosome floating around the cell
         4. Cytoplasm
         5. Ribosomes (make proteins)

      2. Eukaryotes � (Eu- true, karyote � nucleus) do have a nucleus protecting its chromosomes. Examples:
         1. Many unicellular (single-celled) organisms are eukaryotic.
            Examples: Protists (amoeba and paramecium)
         2. Multicellular organisms
            Examples: Animal, plant, and most fungal cells.

      3. Parts of the Eukaryotic Nucleus:
         1. Nuclear envelope - two layer membrane system of the nucleus.
            1. Encases and protects DNA.
            2. Contains large nuclear pores that allow only certain material in and out of the nucleus.
         2. Nucleolus - seen as a smaller dark spot inside the nucleus where ribosomes are made. (Made up of protein and RNA)
         3. Chromosomes - coiled DNA molecules that contain genetic information.

    

    

2. Organelles��little organs� that carries out a particular function or role in a cell. Eukaryotes have increased efficiency in the cell by creating little membrane compartments for the division of labor.
   1. Mitochondria are the �Energy Power Plants� providing 95% of the cells energy.
      1. They extract the energy found in food molecules for the cell to use through a process called cellular respiration.
      2. The mitochondria are bean-shaped organelles, with inner membranes called cristae. These cristae have many folds increasing the surface area for respiration.
      3. The mitochondria are bacteria-like organelles. (It has its own DNA!)

   2. Ribosomes make proteins. �Protein factories�
      1. They are small, round organelles made up of RNA and protein.
      2. They are found floating freely around the cell and attached to ER.

   3. Rough Endoplasmic Reticulum (ER) is the transportation system for the proteins of the cell.
      1. The ER is made up of membranes folded into a tunnel system.
      2. It has ribosomes embedded in its membranes making it appear �rough�. The ribosomes place the proteins they make inside the ER for transport.

   4. Smooth ER makes, stores, and transports hormones and lipids.
      1. It is a membrane tunnel system with no ribosomes attached, making it appear �smooth�.
      2. It is responsible for the detoxification of drugs and other chemicals (in the liver).

   5. Golgi Bodies act as the �Protein - Mail Room�, sorting out and re-packaging similar proteins together.
      1. It is a hollow membrane system that resembles a stack of smashed pancakes.
      2. The Golgi bodies take proteins from the ER and send them through the layers of pancakes, sorting them and packaging them into membrane bubbles.

   6. Lysosomes (lyso- to break, -some�body) act as the �Cleanup Crew� of the cell.
      1. Lysosomes are membrane bubbles containing digestive enzymes that travel around the cell engulfing and destroying worn out organelles.
      2. In single-celled organisms like the amoeba, lysosomes digest organisms the amoeba captures. Lysosomes are created by the Golgi Bodies.

    

    

3. Cell Framework - Cytoskeleton
   1. Microtubules are small hollow tubes made of protein that support the cell.
      1. Microtubules fill the cell like a net. They are able to contract moving organelles around the cell like escalators.
      2. Centrioles are special microtubules used in the reproduction of animal cells. They are not found in plant cells.

      3. In some cells, microtubules provide movement of the cell. Examples:
         1. Cilia - short hair-like structures on the outside of some cells.
            • Cilia help move single-celled organisms like paramecium.
            • Cilia found on lung cells are constantly beating to remove foreign particles.
         2. Flagella � a long, tail-like structure found on the outside of some cells.

    

    

4. Cell Parts found Mainly in Plants
   1. Cell wall - support structure made up of cellulose. This wall is found outside the plasma membrane.

   2. Vacuole � membrane-bound storage bubble.
      1. Plant cells have one very large water storage vacuole, which provides support to the cell.
      2. In animal cells we find smaller vacuoles, but they store proteins, fats, and carbohydrates.

   3. Chloroplasts - organelles responsible for photosynthesis in plants and algae.
      1. Photosynthesis is a process that converts light energy into carbohydrates.
      2. Chloroplasts are bacteria-like. They have their own DNA!

    

    

5. The Endosymbiont Hypothesis states that mitochondria and chloroplasts were at one time independent organisms that were incorporated into other single-celled organisms. They lived in a state of symbiosis, where both benefited. The mitochondria and chloroplast gained protection inside their host cells, while producing extra energy that the host cells could use. These larger host cells, with their energy producing �partners� were able to become more complex, efficient, and specialized.

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