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Cells

This text provides an overview of cell membranes and the different types of organisms, including prokaryotes and eukaryotes. It explains the structure and functions of cell membranes, as well as the distinguishing features of various organism types.

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Cells

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  1. Cells Jason R Mayberry, PhD Castle View High School

  2. Membranes CH3 CH3 CH3 CH3 CH3 Hydrophilic (water loving) Integral Protein CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 OH OH OH OH OH Hydrophobic(water fearing) • The heads of phospholipids are Hydrophilic • The tails of phospholipids are Hydrophobic • Phospholipids line up with their heads next to each other and their tails next to each other • Phosphlipid Bilayer: structure of organic membranes comprised of two layers of Phospholipids lined up with their tails facing each other, so that they don’t have to “see” the water. • “Membranes” like this form spontaneously in water similarly to soap bubbles but are very fragile • Integral Proteins, and Cholesterol (animals) or Phytosterol (plants) molecules mix in with cellular membranes to strengthen them and add functionality. • Carbohydrate groups are bound to some proteins and phospholipid heads.

  3. Summary of Cell/Organism Types Prokaryote: Single celled organism lacking membrane bound organelles (e.g. no nucleus) Bacteria One of the two kingdoms of Prokaryotes; most common. Archaea One of the two kingdoms of Prokaryotes; less common; more extreme. Eukaryote: Single or Multicelled organism with membrane bound organelles (e.g. nucleus) Plant Group of multicellular eukaryotic organisms with chloroplasts and cellulose cell walls. Fungi Group of multicellular eukaryotic organisms lacking chloroplasts, but having chitin cell walls. Animal Group of multicellular eukaryotic organisms lacking chloroplasts and lacking a cell wall. Protists Diverse group of unique eukaryotic organisms that is neither plant, nor fungi, nor animal, and with a wide variety of features.

  4. Prokaryotes – The earliest/simplest cells Plasma Membrane: Outer phospholipid bilayer that compartmentalizes the cell. Average is ~2µm long Cytosol: Aqueous (water) solution in which cell contents are dissolved Cell Wall: Ridged cell wall built primarily of polysaccharides (Carbohydrates) ProkaryoticDNA Flagellum: Rotary protein structure providing locomotion • Nucleoid Region: Contains a single circular strand of DNA (coiled up) • Contains information for making proteins • Also contains smaller circular “plasmid” DNAs in cytosol. Ribosomes: RNA and Protein complexes that synthesize new proteins • Proteins: Many types of proteins found through the cell providing structure an function. • Embedded in the membrane • Dissolved in the cytosol

  5. Two Kingdoms of Prokaryotic Cells Bacteria Archaea Much More Common; Tend to live in normal environments, but some can be extreme. Tend to be extremophiles (live in extreme environments; e.g. hot pools of Yellowstone national park) Where Found Plasma Membrane Typical Double P-headed Monolayer Typical Pseudomurein (and other types of unique carbohydrates) Peptidoglycan(a unique carbohydrate) Cell Wall Proteins for DNA-> RNA-> Protein Unique Similar to Eukaryotes (discussed later)

  6. Typical Eukaryotic Cell Plasma Membrane: Phospholipid bilayer that compartmentalizes the cell; ~75µm long Cell Mem-branes Organelles: Membrane bound compartments inside the cell; specialized for specific tasks. Mitochondria: Power House of the Cell; Completes glucose breakdown to produce ATP for entire cell. Nucleus Contains DNA; Multiple Linear strands Endoplasmic Reticulum Involved in Protein Synthesis and processing Chloroplasts: Capture sunlight and use energy for making carbohydrates Ribosomes: RNA and Protein complexes that synthesize new proteins Peroxisomes Detoxification Golgi Apparatus Protein processing and distribution Vacuole: Storage and other specialized tasks Transport Vesicles Transport proteins to some parts of cell or to outside of cell. Lysosome: Cellular Digestion Carbohydrate Cell Wall

  7. Size Comparison Eukaryotic Organelles make them generally more efficient at carrying out life’s tasks; this allows eukaryotic cells to grow larger.

  8. Eukaryotic Cell Cytoskeleton Cytoskeleton: Protein fibers spread throughout the cell to provide structural and functional support. Microtubules Intermediate Filaments Microfilaments

  9. Types of Eukaryotic Cells Parent cell 1 μm 10 μm Cell wall Buds Vacuole Cell Animal Cells Fungal Cells Nucleus 5 μm Nucleolus Nucleus Yeast cells budding (colorized SEM) Human cells from lining of uterus (colorized TEM) Mitochondrion A single yeast cell (colorized TEM) Cell Flagella 1 μm 5 μm 8 μm Cell wall Chloroplast Nucleus Mitochondrion Nucleolus Protists Plant Cells Nucleus Vacuole Nucleolus Chlamydomonas (colorized SEM) Chloroplast Cells from duckweed (colorized TEM) Cell wall Chlamydomonas (colorized TEM)

  10. Plant Cells and Plants Cellulose microfibrils • Distinguishing Features • Mitochondria and Chloroplasts • Cell Wall made of cellulose • Immotile (cannot move) • No Single Celled Examples • Multicellular • Examples • Moss • Grass • Tulips • Oak • Chloroplast are used to make sugars, which are then used to make other organic molecules. • Chloroplasts break down some of the sugars to make ATP for the entire cell Glycan Plasma membrane Secondary cellwall Pectin Primary cell wall Hemicellulose Mitochondrion 50 nm Plasma membrane Unbranched Cellulose Cell wall Cellulose 6 CH2OH CH2OH OH OH Chloroplast H H 5 3 2 O O H H H H O O 1 4 4 H OH H OH H H H H OH H OH H Wall of adjacent cell 1 O O O H H H H O O 3 2 5 OH OH H H CH OH CH OH 2 2 6

  11. Fungi Cells • Distinguishing Features • Cell Wall made of Chitin (a carbohydrate) • No Chloroplasts • Immotile (Do not move) • Single Cellular Examples: Yeast • Multicellular • Examples: Mold, Mushrooms • Do Not ingest food; Secrete enzymes outside the body to digest it, then absorb it from the environment. Chitin Fungal Cell

  12. Animal Cells • Distinguishing Features • No Chloroplasts • No Cell Wall • Motile (Can move) • Flagellum • Microvilli • No Single Celled Examples • Multicellular • Examples • Sponges (Individual cells are motile before settling down) • Jelly-Fish • Butterflies • Lobster • You • Ingest food (eat) before digestion so can carry it with them as they digest and absorb. Flagellum Microvilli

  13. Protista • Protist: Very diverse group of “Other” eukaryotes that are neither plant, nor fungi, nor animal. • Usually single celled, but sometimes multicelled • Some have a cell wall • Some have chloroplasts • Some are animal like • Some are plant like • Etc.

  14. Summary of Types of Cells Not Alive Cells: capable of independent self-replication (Alive) Inanimate: incapable of replication (i.e. rocks, clouds, stars, dead cells, etc.) ProkaryoticNo Organelles EukaryoticContain Organelles Single Celled Multicelled Bacteria Archaea Protists Plants Fungi Animals Viruses: capable of self-replication but only by manipulating living cells

  15. Tree of Life Universal Common Ancestor • Animals, Plants, and to some extent Fungi are the most conspicuous forms of life. • In terms of abundance and diversity, these three are significantly outweighed by Bacteria, Archaea, and Protists.

  16. Diversity

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