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Transcript
A Look at Cells—Cell Theory, Structure, & Function NOTES (Powerpoint Notes) These notes are based on the information in chapter 3 of your text. There is absolutely no guarantee that every last thing you need to know is here. You need to LISTEN in class, READ the chapter, and PAY ATTENTION to the other activities we do in class. You are responsible for any and all material you are exposed to or have access to (except the entire internet ). Cells are the smallest unit of life that can carry out all the functions of a living organism; not discovered until the invention of the microscope. Organisms can be very broadly classified on the number of cells they are made of. Unicellular organisms are made of only 1 cell; they are the smallest of all living organisms. Ex) some bacteria, many protists Other living organisms are made of many cells and are called Multicellular Ex) Plants, animals, and fungi Shape is related to function Blood cells (hemocytes) - round to move through vessels Nerve - long to carry message to spinal cord Muscle cells for contracting and relaxing The Discovery of Cells Robert Hooke gave the cell its name when viewing cork from an oak tree Anton Van Leewenhoek invented the first “real” microscope and later viewed living organisms (for the first time) in pond water Brown discovered the nuclei of a cells by observing epidermal cells of orchids. Cell Theory Schleiden, a botanist, said “all plants are made of cells” Schwann, a zoologist, said “all organisms are made of cells” Virchow, a physician, said “all new cells come from other cells” These 3 pieces of information are incorporated into the modern cell theory which states: * Cells are the basic unit of life * All organisms are made of cells * All cells come from other cells Basic Cell Structures All cells have some structures in common. All cells have: Cell membrane - phospholipids and protein Cytoplasm - everything inside the cell except the nucleus/DNA Cytoskeleton - system of fibers DNA/RNA - the genetic material Ribosomes - proteins are made on these Cell Membrane See Fig. 11 & 12, p. 60-61 Function: homeostasis 1. controls what enters and leaves the cell 2. boundary separating the cell from its environment Structure: 1. Thin layer of lipids embedded with proteins 2. semipermeable (aka selectively permeable) 3. 2 phospholipid layers called a bilayer 4. hydrophilic head (water loving) 5. hydrophobic tail (water fearing) Cytoplasm Function: Contains or “suspends” structures called organelles inside the cell Structure: 1. Jelly-like base, consisting mainly of water and organic compounds; called the cytosol 2. Other structures within the cytoplasm vary. 3. Contains the cytoskeleton Cytoskeleton: Function: Provides support and a place to anchor other organelles Structure: Composed of protein fibers 3 types: Actin fibers microtubules intermediate fibers DNA All cells contain DNA at some point in their lives Structure: complementary strands in a double helix Function : Carries the genetic code replicates itself to pass the genetic code on to its daughter cells Ribosomes Structure: Spheres composed of RNA and Protein Function: Site of protein synthesis free are shown in the electron micrograph. Ribosomes are also attached to the ER “Typical” animal Cell “Typical” plant Cell note the cell wall! Nucleus – Found only in eukaryotes (all except bacteria) Function: Control headquarters for the cell (brain) Structure: Found in the cytoplasm Contains the genetic material – chromosomes – made of DNA and Proteins Surrounded by a double membrane called the Nuclear Envelope or Nuclear Membrane Inside is a Nucleolus that makes ribosomes Overview of Organelles Eukaryotic cells contain a variety of organelles other than the nucleus. These include: 2 • Endoplasmic Reticulum (ER) – transport system of tubes (1 & 4) •Golgi– stacked sacs that package and distribute materials through the cell (2) 3 1 Vesicles – membrane-bound sacs for transport of proteins (3) 4 •Vacuoles – tiny membrane-bound storage containers •Lysosomes (animal cells only) – contain digestive enzymes, “suicide sacs” •Mitochondria – function in the 2nd part of Respiration, taking the energy from small carbon compounds and storing it in ATP; have their own DNA “powerhouse of cell” •Centrioles– function in cell division (animal cells only); always 2 present at right angles to each other; referred to collectively as the centrosome •Chloroplast – type of plastid containing chlorophyll; functions in photosynthesis (plant cells and a few protists only) ; have their own DNA •Central Vacuole (plant cells only) – large central structure for storing water and its solutes Organelles—A Closer Look at a Few Nucleolus: Location—within the nucleus; Structure—knot of chromatin; Function—produce ribosomes Endoplasmic Reticulum (Rough): Structure—Network of membranes near nucleus, contains ribosomes on surface; Function—transports proteins made by the attached ribosomes through the cell to the golgi. Endoplasmic Reticulum (Smooth): Structure—Network of folded membranes throughout cell, Contains no ribsomes on surface; Function—Makes lipids and breaks down toxic substances. Golgi Apparatus: Location—in the cytoplasm; Structure—closely stacked, flattened membrane sacs; Function— stores, packages, and transports products (proteins) inside for use outside; vesicles (a bit of golgi pinches for transport of stored materials) Lysosome: Not found in plants; Structure—saclike, contains digestive enzymes; Function—digests food particles, old organelles Mitochondria: Found in ALL eukaryotic cells; Strucure--oval, complex matrix of folded membranes to increase surface area; Function—changes energy stored in food into a more useful form, the energy storage molecule called adenosine triphosphate (ATP) Centrioles: Found in Animal cells only; Structure—9 sets of 3 protein fibers; Function—aid in the division of chromosomes during mitosis. Microtubules: Location—throughout the cell’s structure; Structure—thick filaments made of protein; Function— gives structure & shape to cells and anchors organelles Microfilaments: Location—thoughout the cell structure; Structure—thin, protein tubes; Function—allows for elasticity and movement within cells Vesicles: Location—inside or outside of the plasma/cell membrane; Structure—bits of membrane from the plasma membrane or the golgi apparatus; Function--Vesicles fuse with the cell membrane may be used to release or transport chemicals in or out of the cells. Exocytosis out of the cell; Endocytosis into the cell Vacuole: Location—cytoplasm; Structure—sac of fluid surrounded by a membrane; Plants--large in size, Animals— small in size; Function—sites of storage of water, ions and some nutrients. Plants: allows plants to maintain turgor pressure. Chloroplast: Location—plant cells and some protests; Structure—double phospholipids bilayer, Inner layer (stacks=grana; Non stacked area = stroma); Function—capturing radiant energy and converting it to chemical energy, chlorophyll is the green pigment that traps the energy from the sun. Vesicles, golgi, and ER are all involved in protein production in the cell. They are found in both plant and animals cells. Mitochondria are found in both plant and animal cells. They are involved in cellular respiration. ONLY IN ANIMALS: Centrioles are only found in animal cells. They were thought to be involved in cell division. Lysosomes contain digestive enzymes for breaking down toxins and worn out organelles, invading cells, or “food” for phages. ONLY IN PLANTS: Choloroplasts are found only in plant cells. They take in light energy and store it in carbohydrates during photosynthesis. Note the cell wall (contains cellulose, provides structure & support) and large central vacuole (stores water) in the diagram of a plant cell. They are also found only in plant cells. Flagella and Cilia: Location—outside of cells; Structure—Cilia (short hair-like), Flagella (long whip-like tail); Function--locomotion=movement, Cilia (tiny, flutters of movement), Flagella (one big wave motion) Some Cell Web Sites for Further Study http://sun.menloschool.org/~cweaver/cells/ •http://www.borg.com/~lubehawk/cell.htm •http://www.rkm.com.au/CELL/ •http://www.enchantedlearning.com/subjects/biology/cells/ •http://web.jjay.cuny.edu/~acarpi/NSC/13-cells.htm •http://www.rkm.com.au/BACTERIA/bacterial-cell.html http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html#Golgi%20Apparatus%20and%20Dictyosomes