Cell Structure1 Chapter 4: Cell Structure Topics you are not responsible for: Bacterial cell walls and the Archaea Cell-to-cell interactions End of Chapter questions: Understand: all Apply: all Synthesize: 1, 3, 4 Do all mQuiz questions TEM of Platinum/Carbon replicas of HeLa cell cytoplasm showing clathrin- coated vesicles and microtubules Inner Life of The Cell

Cell Structure2 What happens to A  after it forms? External Amyloid plaques Internal Neurofibrillary tangles -- Tau protein “Trafficking” of membrane components Exportto cell surface -- APP, secretases, etc. Import into cell Questions Do plaques and/or tangles cause Alzheimer’s Dis.? Why do neuro. tangles form?

Cells and Organs3 Leukocyte Rolling Leukocyte Homing Cells of you immune system circulate continuously through your body Circulation of cells and Interstitial fluid -- antigens / pathogens -- immune cells Cell extravasation -- Chemokines -- receptors -- adhesion proteins

Cell Structure4 Light Microscopy (A-C) A Bright FieldDIC B DIC Video Confocal 3D imaging Electron Microscopy D E TEMSEM Fluorescence C

Cell Structure5 Examples of Electron Microscopy D. TEM (Transmission Electron Microscopy) of neurons (cross- section) showing internal cellular structures. ttp://visualsunlimited.photoshelter. com/image/I00005SIGjGWwl9U ttp://visualsunlimited.photoshelter. com/image/I00005SIGjGWwl9U E. SEM (Scanning Electron Microscopy) of neurons showing external surface structures. em/nerv03.sem.html Examples of Light Microscopy A. Standard Bright Field Microscopy of Histological section of brain stained to show Neurofibrillary Tangles (>) and Aβ plaques (*). uk.org.uk/mag //artsep06/mc-Alzheimer.htmlhttp:// uk.org.uk/mag //artsep06/mc-Alzheimer.html B. DIC (Differential Interference Microscopy) of Neocortical neurons in primary culture. Note accentuation of edges and 3D-like appearance Adapted from bin/standard.cgi?descriptif=mantegazza.txt&dossier 1=equipes&dossier2=mantegazza&site=inter&men u=1&ssmenu=14&lang=ukhttp:// bin/standard.cgi?descriptif=mantegazza.txt&dossier 1=equipes&dossier2=mantegazza&site=inter&men u=1&ssmenu=14&lang=uk C. Fluorescence Microscopy of fibroblast cell culture stained for proteins of the nucleus, mitochondria, and peroxisomes, as well as the filamentous actin and intermediate filaments. digitalimages/muntjac/muntjaclarge10.html digitalimages/muntjac/muntjaclarge10.html

Cell Structure6 How do Eukaryotic cells differ from Prokaryotic cells? Prokaryotes = bacteria Eukaryotes = everything else Size Cytoplasm organization Structure of chromosomes We will discuss other differences later Eukaryotic cell cytoplasm

Cell Structure7 How big are cells? Why are cells so small? Surface to volume (S/V) ratio How Big is It?

Cell Structure8 What are some functional regions of cells? Cytoplasm Cell membrane (plasma membrane) Extracellular structures Cell wall Cilia & flagella EC matrix

Cell Structure9 What are the components of eukaryotic cytoplasm? Membrane bound compartments -- Cytoplasm vs “cytosol” Molecular building blocks Proteins/enzymes -- Cytoskeleton Ribosomes

Cell Structure10 What is the structure of the nucleus? Large nuclear pores -- two membranes Chromosomes Nucleolus

Cell Structure11 How do molecules move through the cell? 1) Diffusion 2) Endomembrane transport system What is transported? Where to? Endocytosis & exocytosis Molecular Diffusion Know this!

Cell Structure12 What is the structure and function of the ER? Beginning of endomembrane transport Rough ER Protein: -- synthesis (Ribosomes) -- folding -- modifications (glycosylation) Smooth ER Lipid synthesis Ca++ storage Transport to Golgi Cell structure Transport vesicles

Cell Structure13 What is the structure & function of the Golgi? Protein modifications -- e.g., glycosylation Sorting & Packaging into vesicles View these animation Virtual cell -- Protein Trafficking Virtual cell – Protein modification Links on Class resource page How are proteins transported Through the Golgi?

Intracellular Transport14 How are proteins modified within the golgi? How are enzymes ‘tagged’ for transport to lysosomes? -- hydrolytic enzymes -- NAcGluAm-P transferase -- mannose-6-P -- M-6-P receptors

Cell Structure15 What is the function of lysosomes? Breakdown of: Intracellular materials Extracellular materials How are materials transported to lysosome ? Hydrolases from Golgi Materials from inside and outside the cells

Cell Structure16 Mutations to transport processes underlie some genetic diseases I-cell diseases Accumulation of lysosomes Mental retardation Metabolic abnormalities Fatal Mucolipidosis II NAcGluAm-P transferase deficiency What is expected effect? Tay-Sacks disease ganglioside G M2 lipase deficiency -- lipid recycled from cell surface What is expected effect? Lymphocytes of Mucolipidosis II

Cell Structure17 What are functions of chloroplasts and mitochondria? What are distinctive properties Double membrane Presence of DNA What is the origin of these organelles? “Endosymbiosis” 70S vs 80S ribosomes Endosymbiosis

Cell Structure18 What proteins comprise the cell cytoskeleton? Intermediate filaments Microtubules Actin filaments How is the “cytoskeleton” different from a animal skeleton? Organization and function of Intermediate filaments Mechanical strength

Cell Structure19 What are the organization and functions of microtubules? cytoplasmic transport chromosome movements movements of flagella and cilia -- “9+2” structure Cytoplasmic streaming Closer view on microtubules FlagellaCilia

Cell Structure20 What are the organization and functions of actin filaments? Various types of cell movements Membrane contractions muscle contraction Crawling motions Interacts with “myosin” Heart CellMembrane ruffling

Cell Structure21 How do plant cells differ from animal cells ? Chloroplasts Cell Wall Vacuole

Cell Structure22 How are viruses different from cells? Much smaller Protein coat – ‘capsid’ Often no membrane No metabolism Why are virus infections Very difficult to treat?