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Transcript
Chapter 7 Cell Structure and Function The discovery of cells was dependent on the invention of the microscope The Cell Theory 1. All organisms (bacteria, protists, fungi, plants, animals) are made of cells. 2. Cells are the basic unit of structure and function of living things. 3. All cells come from preexisting cells. Important Scientists • Hooke discovered and named cells Early Microscopes = Light Microscopes, where light reflects off an object. Usually cannot see most organelles with these. Van Leeuwenhoek’s Microscope Original Copy An old German Microscope Stains add contrast. Some can identify chemical types Acid-secreting cells of Rattlesnake Venom Glands From: Zoologischer Anzeiger - A Journal of Comparative Zoology Volume 245, Issues 3–4, 24 November 2006, Pages 147–159 Bioweapons synthesis and storage: The venom gland of front-fanged snakes ☆ Stephen P. Mackessy, , Louise M. Baxter School of Biological Sciences, University of Northern Colorado, 501 20th St., CB 92, Greeley, CO 80639-0017, USA Fluorescent Stains Human height 1m Length of some nerve and muscle cells 0.1 m Chicken egg 1 cm Unaided eye Microscopes are almost always needed to see a cell. Frog egg Old terminology: micron Most plant and animal cells 10 µm Nucleus Most bacteria 1 µm Mitochondrion 100 nm Smallest bacteria Viruses Ribosomes 10 nm Proteins Lipids 1 nm Small molecules Atoms Electron microscope Size: 1-100 micrometers (= µm) 100 µm Light microscope 1 mm Electron Microscopes Today (Note Problem: Cells are not alive) SEM = Scanning See surface See 3-D TEM = Transmission Thin Section; see through See 2-D Important Scientists • Schleiden determined that all plants are made of cells. • Schwann determined that all animals are made of cells. Important Scientists Van Leeuwenhoek discovered that microorganisms live in a huge variety of sources (pond water, rivers, his mouth). Virchow claimed that all cells come from preexisting cells. The Two Cell Types Prokaryotes and Eukaryotes Prokaryotes = Bacteria and BlueGreen Algae CHARACTERISTICS • Simple • Coffee bean size • No membrane-bound organelles but do have ribosomes (rRNA) • Have DNA, but not in a nucleus Organelle = “little organ” Bacteria Types Cocci (round) Bacillus (rod) Spirillum (spiral) What good are bacteria? • Autotrophs – Produce oxygen • Fix nitrogen – So plants can take it in. We need nitrogen to make DNA & proteins • • • • Recycle nutrients Form antibiotics Help in digestions and formation of vitamins Production of cheese and yogurt Eukaryotes Characteristics – More complex – Larger compared to prokaryotes – Cell membrane; plants and fungi ALSO have cell walls – Membrane bound organelles – DNA in nucleus Eukaryotes Organelles are important in keeping noncompatible reactions apart, yet allowing them to happen at the same time = DIVISION OF LABOR The Basic Animal Cell = Nucleus + Cytoplasm (Cytoplasm = organelles + cytosol) Plasma Membrane Controls what goes in and out. A phospholipid bilayer. Embedded proteins involved in transport. Carbohydrate side chains involved in cell-to-cell recognition. Endocytosis and Exocytosis How larger particles get into and out of a cell Is this green particle inside the cell? Basic Plant and fungi cells also have cell walls for support and protection Walls are typically made of cellulose (plants) or chitin (fungi). NUCLEUS Nuclear envelope Nucleolus Chromatin Rough endoplasmic reticulum TYPICAL Smooth endoplasmic PLANT reticulum Ribosomes CELL Central vacuole Golgi apparatus Microfilaments Intermediate filaments Microtubules Mitochondrion Peroxisome Chloroplast Plasma membrane Cell wall Plasmodesmata Wall of adjacent cell CYTOSKELETON Nucleus Contains chromosomes which are DNA wrapped around protein spools. • Recall that DNA has the code that tells the cell what proteins (enzymes) to make. • Uncoiled chromosomes are called chromatin Also contains nucleoli = areas where rRNA and tRNA are made. Surrounded by a nuclear envelope that has pores in it. Vacuoles Found in plant cells; store water, digestive enzymes, salts, pigments, etc. For support. Vesicles Found in all cells. Store digestive enzymes or other chemicals, transport chemicals, Lysosomes Contain enzymes to break down food brought in by endocytosis; can also break down own molecules and organelles for recycling. Cytoskeleton A network of protein fibers that help the cell keep its shape and helps things move around (like a freeway). Some help the cell move. Cilia Short flagella, often arranged in rows, that help the cell move. Typically hundreds. Primary Cilia Some are chemosensitive, some pressure sensitive. Function in cell signaling, cellular development, and responsible for many diseases. Ribosomes The site of protein synthesis Endoplasmic Reticulum A system of tubes Rough ER: Lipid components of the cell membrane are made here. Proteins destined for export, or to become part of the cell membrane, or digestive enzymes are modified here. Smooth ER: Lipid components of the cell membrane are also made here. Involved in the detoxification of drugs. Golgi Apparatus Where proteins from the ER are further refined and packaged for either storage in the cell or final transport out of the cell. Mitochondria Break down food to produce ATP. This process is called cellular respiration Chloroplasts “Solar Power Plants.” They capture light energy and convert it to chemical energy (sugar). This process is called photosynthesis. NOTE: Both have their own DNA