Chapter 4

 Schwann, Schleiden and Virchow are credited with coming up with the basics of the cell theory  3 components: ◦ 1.All living organisms are made up of cells ◦ 2.Cells are the basic units of structure and function in living organisms. ◦ 3.All cells come from cells that existed before them by cellular reproduction. 

 Every cell has the following main characteristics: ◦ Cell membrane ◦ Cytoplasm ◦ DNA ◦ Ribosomes

 Antone von Leeuwenhoek assembled the first microscope that was useful for scientific research.  Compound light microscopes reflect light through a set of lenses and the specimen to magnify the specimen.  See handout for the parts of the microscope – you must know it. 

 Two important characteristics that determine the quality of a light microscope: ◦ Magnification – an increase in the apparent size of an object. We calculate magnification by the following: Magnification of eyepiece x magnification of objective lens = total magnifying power Resolution – the measure of clarity of an image. As the magnification increases, the resolution of the image decreases.

 Some microscopes use beams of electrons for magnification instead of light – electron microscopes  Scanning electron microscope (SEM) – used to study the detailed architecture of the surface of the object. Forms a 3D image, but does not show the inside of the object.  Transmission electron microscope (TEM) – used to provide a detailed 2D image of the inside structure of the object that is viewed.

  Cells are microscopic, they are visible only with light microscopes.  Most of their size ranges from µm.  Cells are small, because they have to be able to carry materials from one side of the cell to the next in a short period of time.  Cells must have a large enough surface area to be able to take in nutrients and oxygen and release waste quickly.

 Prokaryotic cells – ◦ small cells (about 1-10 µm) that do not have a nucleus and membrane-bound organelles ◦ Found in bacteria and archaebacteria

 Prokaryotic Cell Organelles: ◦ Nucleoid region – part of the prokaryotic cell where the DNA is found ◦ Cell membrane – innermost covering of the cell ◦ Cell wall – outside of cell membrane, made up of a special mix of polysaccharides and proteins (antibiotics break it down) ◦ Capsule – outside of the cell wall, protective covering (not all bacteria have it) ◦ Flagella (sing. Flagellum) – long, whiplike structure that moves bacteria ◦ Pili – short, hair-like projection used to stick to other surfaces and for conjugation (exchange of genetic materials between bacteria) ◦ Cytoplasm – jelly-like fluid that dissolves substances and holds organelles ◦ Ribosomes – organelles that make proteins in the cytoplasm

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 Protists, Fungi, Plants, and Animals  Have nucleus and membrane-bound organelles  Much larger and more complex than prokaryotic cells.  Reproduce sexually and asexually

 Nucleus ◦ Control center of cell; contains most of the cell’s DNA  Nucleolus ◦ Location where ribosomes are synthesized  Nuclear pore ◦ Allows RNA to move in and out of nucleus

 Ribosomes ◦ Protein synthesis  Rough ER ◦ Comprised of a network of tubes and flattened sacs. ◦ Continuous with plasma membrane and nuclear membrane ◦ Site of protein synthesis (consists of ribosomes)

 Smooth ER ◦ Site of lipid and carbohydrate metabolism ◦ No ribosomes  Golgi Apparatus ◦ Connected with ER; flattened disc-shaped sacs, stacked one on top of the other ◦ Modification, storage, and packaging of proteins. ◦ “tags” proteins so they go to the correct destination.

 Lysosomes (in animal cells and some protists) ◦ Digestion of nutrients, bacteria, and damaged organelles; destruction of certain cells during embryonic development  Peroxisomes ◦ Diverse metabolic processes with breakdown of H 2 O 2 by-product  Vacuoles ◦ Digestion (like lysosomes); storage of chemicals, cell enlargement; water balance

 Chloroplasts ◦ Conversion of light energy to chemical energy of sugars (site of photosynthesis)  Mitochondria ◦ Conversion of chemical energy of food to chemical energy of ATP ◦ “Power House” of cell ◦ Bound by double membrane

 Cytoskeleton (including cilia, flagella, and centrioles in animal cells) ◦ Maintenance of cell shape; anchorage for organelles; movement of organelles within cells; cell movement; mechanical transmission of signals from exterior of cell to interior.  Cell walls (in plants, fungi, and protists) ◦ Maintenance of cell shape and skeletal support; surface protection; binding of cells in tissues