Chapter 7 Robert Hooke: 1665 - looked at a thin slice of cork Anton van Leeuwenhoek: 1674 - observed living cells in pond water In 1839, Schwann and Schleiden suggested that cells were the basic unit of life. In 1855, Rudolf Virchow concluded that all cells come from pre-existing cells. 1. 2. 3. All living things are composed of cells Cells are the basic units of structure and function in living things New cells are produced from existing cells Cells that do not contain a nuclei. Generally smaller and simpler than eukaryotic cells. EX: Bacteria Contain a nucleus where genetic material is separated from the cell by a membrane – “membrane bound” Larger and more complex Contains specialized structures (organelles) and internal membranes Some are single-celled, others are large, multicellular organisms A factory with different tasks performed at different locations within the factory. 1 Nucleolus 2 Nucleus 3 Ribosomes (little dots) 4 Vesicle 5 Rough endoplasmic reticulum 6 Golgi apparatus 7 Cytoskeleton 8 Smooth endoplasmic reticulum 9 Mitochondria 10 Vacuole 11 Cytosol 12 Lysosome 13 Centrioles within Centrosome 14 Cell membrane Means “little organs” Cytoplasm: ◦ Liquid/gelatenous part of the cell where organelles are suspended Nucleus: ◦ Contains the DNA (coded instructions for making proteins and other important molecules) ◦ Cell Song http://www.youtube.com/watch?v=ZK6YP1Smbxk Nuclear envelope (membrane): surrounds the nucleus ◦ Dotted with nuclear pores that allow material to move into and out. ◦ RNA, DNA, and protein can move in and out. ◦ Chromatin: grainy material in the nucleus ◦ Chromosomes: condensed chromatin ◦ Nucleolus: dense circular area inside, where assembly of ribosomes begins Proteins are assembled here!!! Found throughout the cytoplasm Produce proteins by following coded instructions from the nucleus. Internal membrane system The site where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell. Rough ER: involved in the synthesis of proteins. ◦ Contains ribosomes Smooth ER: contains collections of enzymes that perform specialized tasks. Ribosomes are not found on it. Synthesis of membrane lipids and the detoxification of drugs. Modify, sort, and package proteins and other materials from the endoplasmic reticulum for storage in the cell or secretion outside the cell. Small organelles filled with enzymes. Digestion, or breakdown of lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell. Also breaks down organelles that have outlived their usefulness Tay-Sachs disease: traced to lysosomes that fail to function properly. Mitochondria: organelles that convert the chemical energy in food into compounds more convenient to use. Makes energy Composed of two membranes: ◦ Outer and inner membranes ◦ Folded inner membranes increase surface area for more energy production ◦ Mitochondria come from the cytoplasm of the egg cell ( from mother) Chloroplast: capture energy from sunlight and convert it into chemical energy in a process known as photosynthesis. Found in plants and photosynthetic organisms. Surrounded by two membranes: Contain green pigment called chlorophyll Helps support the cell. A network of protein filaments that maintains cell shape. Also involved in movement. Microfilaments: threadlike structures made of a protein called actin. Produce a tough flexible framework that supports the cell. Microtubules: hollow structures made up of proteins known as tubulins. ◦ Play a role in cell shape ◦ Important in cell division ◦ Cilia and flagella: movement Centrioles: located near the nucleus and helps to organize cell division. ◦ Not found in plant cells Regulates what enters and leaves the cell Composition: lipid bilayer Fluid Mosaic Model Transport and channel proteins: help to move material across the cell membrane. Carbohydrates: allow individual cells to identify one another Lie outside the cell membrane. provide support and protection for the cell. Cellulose: principle component of cell wall the mass of the solute in a given volume of solution Equilibrium: when the concentration of the solute is the same throughout the system Particles move from an area of high concentration to an area of low concentration. Does not require energy The diffusion of water through a selectively permeable membrane. Isotonic: the concentration of solutes is the same inside and outside the cell Hypertonic: solution has a higher solute concentration than the cell Hypotonic: solution has a lower solute concentration than the cell. Molecules that cannot diffuse across the cell membrane’s lipid bilayer on their own move through protein channels instead. No energy is required against the concentration gradient (low to high). Requires energy Carried out by transport proteins. Taking material into the cell by means of infoldings, or pockets, of cell membrane ◦ Phagocytosis ◦ Requires considerable amount of energy the membrane of the vacuole surrounding the material fuses with the cell membrane forcing the contents out of the cell.