Chapter 2: The Cell - Biology PDF

Image Source: https://www.behance.net/gallery/15570899/Cell-Collage The Cell: An Overview Chapter 2  Key concepts 1. All organisms are made up of cells 2. The cell is the basic unit of function and structure 3. All cells share some common structures/characteristics...

Image Source: https://www.behance.net/gallery/15570899/Cell-Collage The Cell: An Overview Chapter 2  Key concepts 1. All organisms are made up of cells 2. The cell is the basic unit of function and structure 3. All cells share some common structures/characteristics 4. There are some differences between cells within and between different organisms Image Source: https://www.proprofs.com/flashcards/upload/q4753561.png  Why are cells important? Vital in understanding various aspects of biology but also in agriculture, biotechnology, and many aspects of health and disease Image Source: https://unsplash.com/s/photos/biotechnology Image Source: https://www.sciencefocus.com/science/what-is-lab-grown-meat-a-scientist-explains-the-taste-production-and-safety-of-artificial-foods Image Source: https://cals.ncsu.edu/news/crispr-plants-new-non-gmo-method-to-edit-plants/  The first look Robert Hooke 1655 Small rooms used by monks - cella  Cell theory Mid-19th century, microscopic observations had yielded three generalizations = cell theory All organisms are composed of one or more cells The cell is the basic structural and functional unit of Cells arise only all living organisms from the division Schleiden – plants of preexisting cells Schwann – animals Image Source: Screen capture from the TED Ed Virchow saw cells video, “The Wacky History of Cell Theory.” divide under microscope  Basic features of cell structure and function Basic structural and functional Essential processes of life unit Image Source: https://biologywise.com/plant-animal-cell-similarities Contain genetic information Use energy, respond to changes in environment, reproduce, and pass on hereditary information  Many kinds of cells Unicellular organisms Functional independent organism – carry out all necessary activities Multicellular organisms (plants and animals) Activities of life divided with specialized cells  Sizes of cells Most cells are microscopic Size of cell not related to body size Related to function Image Source: https://www.toppr.com/ask/content/story/amp/cell-and-its- discovery-123264/  Why are cells so small? Cell size limited by surface area-to-volume ratio As cell gets larger there comes a time when its surface area is not large enough to meet the demands of the cell volume Cell will stop growing  How can we look at cells? Microscopy Visualization of cells and microorganisms by magnifying their images to make them larger Image Source: https://micro.magnet.fsu.edu/primer/museum/hooke.html  Magnification The number of times larger an image is than the real size of the object M = I/A I = observed size of the image A = actual size Low magnification Its like zooming in See less but in more detail High magnification Depends on lens system Image Source: https://www.slideshare.net/1slid/3-microscope-lab-thursday-91213  Resolution Minimum distance that two points in specimen can be separated and still be seen as two points The higher the resolution, the greater the detail we can see Affects sharpness of object Higher magnification increases resolution Depends on wavelength of light used Image Source: https://slidetodoc.com/microscopes-magnifications-resolutions-and-calculations- light-microscope-uses/ Magnification vs Resolution Image Source: https://open.oregonstate.education/cellbiology/chapter/microscopy/  Contrast Variation of color and shadow Allows human eye to focus on different aspects of image and to register depth Stains and staining techniques Method of illumination Higher contrast gives more detail, but can’t increase Picture showing low contrast, high contrast and phase resolution contrast Image Source: https://player.slideplayer.com/27/9157951/#  Light microscopy Use visible light (400-700 nanometers) to illuminate specimen a. Range of the electromagnetic spectrum The shortest, most Range of most Range of heat The longest, energetic radiation reaching the escaping from the lowest-energy wavelengths surface of Earth surface of Earth wavelengths Gamma X-rays Ultraviolet Near-infrared Infrared Microwaves Radio rays radiation radiation radiation waves Visible light 400 450 500 550 600 650 700  Light microscopy Allows magnification of about 1000x Resolution of about 0.2 μm Very versatile Image Source: https://microbenotes.com/light-microscope/  Light microscopy Use natural color or add stain Developing seed coat of the model plant Arabidopsis thaliana stained with toluidine blue Epithelial cells of a human gall bladder, stained with hematoxylin and eosin (H&E) Image Source: https://open.oregonstate.education/cellbiology/chapter/microscopy/  Light microscopy Subtypes of light microscopy Types of light that you are viewing when you look at an image Transmitted light microscopy Sample between light source and eyepiece Light passes through sample Image Source: https://open.oregonstate.education/cellbiology/chapter/microscopy/  Light microscopy Subtypes of light microscopy Types of light that you are viewing when you look at an image Emitted light microscopy Light source off to the side Molecules in sample get excited Release own photons Light come from samples themselves Image Source: https://open.oregonstate.education/cellbiology/chapter/microscopy/  Fluorescence Property of some molecules Absorbs energy of a photon Gets excited/moved to higher energy state Electron returns to ground state (less excited) Releases a less energetic / longer wavelength photon Fluorescence emission  Fluorescence microscopy Uses much higher intensity light source (like UV light) Excites a fluorescent species in a sample of interest Fluorescent species in turn emits a lower energy light of a longer wavelength that can be detected Image Source: https://www.en.silicann.com/blog/post/what-is-fluorescence/  Fluorescence microscopy Label (or tag) specific macromolecules / cell structure so that we can track them within the cell Tag structures using fluorescent molecules (called fluorochromes or fluorophores) blue = nucleus red = actin green = microtubules Mouse fibroblasts, Green: F-Actin, FITC, Red: Tubulin, Cy5, Blue: Nuclei, DAPI. Courtesy of: Dr. Günter Giese, Max Planck Institute for Medical Research, Heidelberg, Germany. Image Source: https://www.leica-microsystems.com/science-lab/life-science/fluorescent-dyes//  Electron microscopy Use electrons to illuminate specimen Shorter wavelength than visible light Higher resolution images Image Source: https://ib.bioninja.com.au/standard-level/topic-1-cell-biology/11-introduction-to-cells/microscopes.html  Electron microscopy Use electrons to illuminate specimen Shorter wavelength than visible light Electron microscope Light microscope Higher resolution images (Ability to distinguish separate and distinct objects) 1nm 400nm Image Source: https://quizlet.com/gb/760892366/lecture-8-the-electron-microscopehistory-principles-applications-flash-cards/  Transmission Electron Microscopy Pass electrons through specimen to generate a cross-section Very thin slices of tissue using an ultramicrotome Chemically preserved / fixed and dehydrated Stained with heavy metal (lead) Cotton phloem tissue. Sieve element (top cell) and a companion cell (bottom cell), TEM x8,000. Photo by J. Thorsch. Image Source: https://www.ccber.ucsb.edu/ucsb-natural-history-collections- botanical-plant-anatomy/transmission-electron-microscope  Scanning Electron Microscopy Scatter electrons over a surface to differentiate depth and map in 3D Chemically preserved / fixed and dehydrated Coated/Stained with heavy metal (gold / palladium / Butterfly wing under scanning electron platinum / silver) microscopy. Image Credit: ClaudiaSEM/Shutterstock.com Image Source: https://www.azolifesciences.com/article/Scanning-Electron-Microscopy- %28SEM%29-An-Overview.aspx  Comparison Light Microscopy Electron Microscopy Glass lenses Electromagnetic “lenses” Live or dead cells Only dead cells Stained with coloured dye Coated with heavy metals Less resolution (0.25 to 0.3 More resolution (0.001 µm) µm) Less magnification (500 to More magnification (more 1500x) than 10 000x) Colour images B/W images*  What is common to all cells? What features are shared by all cells (prokaryotic cells and eukaryotic cells)?  The outer boundary All cells are surrounded by plasma Cell 1 membrane Cell 2 Bilayer Lipids with embedded protein molecules Hydrophobic barrier to water-soluble substances  The outer boundary Selected substances can penetrate Cell 1 cell membranes - transport protein channels Cell 2 Selective transport of ions and water- soluble molecules Maintains specialized internal environments  Inside the cell Plasma membrane Cytoplasm (organelles and Cytoskeleton cytosol and cytoskeleton) Protein based Cytosol network of Aqueous solution filamentous structures containing ions, various Central region of all Maintains cell shape organic molecules, and cells (DNA molecules - Plays key roles in cell organelles store hereditary division and information (genes) chromosome segregation  Inside the cell Plasma membrane Cytoplasm (organelles and cytosol and cytoskeleton) Makes molecules Receives signals for growth and from exterior and reproduction and carries out conversion of Central region of all chemical chemical and light cells (DNA molecules - reactions in energy store hereditary response information (genes)  How do prokaryotic and eukaryotic cells differ? Extensive membrane systems Varying internal membranes that form organelles Bacteria and Archaea Nucleoid region with no boundary Eukaryotes membrane Membrane-bound compartment nucleus  Prokaryotic cells Image Source: https://letstalkscience.ca/educational-resources/backgrounders/introduction-bacteria  Prokaryotic cells Nucleoid Single, circular molecule (prokaryotic chromosome) DNA used to make Messenger RNA (mRNA) molecules Carried to ribosomes (in cytoplasm) - assemble amino acids into proteins Ribosomes = rRNA + protein  Prokaryotic cells Plasma membrane Transport in and out of cell Site of metabolic reactions Cellular respiration Photosynthesis  Prokaryotic cells Cytoskeleton Maintain cell shape and functions in cell division Movement Bacterial flagellum rotates in socket and pushes cell through liquid medium Attachment Hairlike pili attach cell to surfaces or other cells Sex pilus joins bacteria during mating (conjugation) Image Source: https://byjus.com/question-answer/what-is-the-main-difference- between-flagella-and-pili/  Prokaryotic cells Rigid external cell wall. Often coated with external polysaccharide layer (glycocalyx) Glycocalyx loosely associated with cells = slime layer Glycocalyx firmly attached = capsule Protection and attachment Image Source: https://www2.nau.edu/~fpm/bio205/Sp-10/Chapter-04.pdf  Eukaryotic cells Image Source: https://animalcellstructure.blogspot.com/2014/03/plant-cells-and-animal-cells.html  Eukaryotic cells Nucleus Membrane-bound compartment Cytoplasm Membranous organelles Specialized functions Cytoskeleton supports and moves cell structures Cytosol Supports energy metabolism and intracellular traffic  Plasma membrane and Cell wall Plasma membrane with embedded Supportive cell wall surrounds plasma proteins membrane (plant, fungi, some protists) Image Source: https://www.earthslab.com/physiology/cell-membrane-plasma-membrane-structure-function-composition/  The nucleus Nuclear envelope Consists of two membranes (layered) Selectively permeable Nuclear pore complex Embedded in nuclear envelope Nucleoporins Regulates transport of proteins and RNA molecules between nucleus and cytoplasm Nuclear pore Channel through nuclear pore complex The nuclear envelope  The nucleus Chromatin Combination of DNA and proteins that fills space inside nucleus Uncondensed / Unwound Nucleolus (pl. nucleoli) Small masses - protein, RNA and DNA Form around genes coding for rRNA molecules (rDNA) Ribosome biogenesis Image Source: https://www.britannica.com/science/nucleolus One or more in nucleus  The nucleus Chromosome Eukaryotic chromosome Condensed chromatin One complete DNA molecule and its Found only during cell division associated proteins Image Source: https://micro.magnet.fsu.edu/cells/nucleus/chromatin.html  Eukaryotic ribosomes Consists of a large and a small subunit Comprises RNA and proteins Formed in nucleoli and exit nucleus through nuclear pore complexes In cytoplasm, they join on mRNAs to form ribosomes Expression of genes (translation)  Eukaryotic ribosomes Image Source: https://www.open.edu/openlearn/science-maths-technology/a-tour- the-cell/content-section-4.4 Image Source: https://reports.news.ucsc.edu/breakthrough/revealing-the-ribosome/  Eukaryotic ribosomes Ribosomes can be freely suspended in the cytosol or attached to membranes Free Attached May remain in cytosol, pass into Attached to membranes: nucleus, or become parts of nuclear envelope or mitochondria, chloroplasts, endoplasmic reticulum (ER) cytoskeleton, or other cytoplasmic Follow special path to other structures. organelles in cell In nucleus become part of chromatin, nuclear envelope, or remain in solution