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General Biology: A Tour of the Cell

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  • Who first observed cells and cell walls?
    Robert Hooke was the first recorded person to observe cells and cell walls in the 1600s-1700s.
  • What did Antoni van Leeuwenhoek contribute to microscopy?
    He created his own microscopes and observed 'animalcules', early observations of microorganisms.
  • What is the principle of a Light Microscope (LM)?
    Visible light passes through a specimen and glass lenses that refract the light to magnify the image, up to ~1,000x life-size.
  • Define magnification in microscopy.
    Magnification is the ratio of an object's image size to its real size.
  • What is resolution in microscopy?
    Resolution is the measure of image clarity, the minimum distance two points can be separated and still be distinguished.
  • Why is contrast important in microscopy?
    Contrast is the difference in brightness between light and dark areas, helping distinguish structures in the image.
  • What are the limitations of Light Microscopes?
    LMs cannot resolve most subcellular structures and organelles because they are too small to be seen clearly.
  • What is the main difference between Scanning Electron Microscopes (SEM) and Transmission Electron Microscopes (TEM)?
    SEM focuses electrons on specimen surfaces producing 3D images; TEM passes electrons through specimens to study internal structures with higher resolution.
  • What is cell fractionation?
    A technique that breaks cells and separates components by centrifugation based on size to isolate organelles for study.
  • What are the basic features common to all cells?
    All cells have a plasma membrane, cytosol, chromosomes, and ribosomes.
  • How do prokaryotic cells differ from eukaryotic cells?
    Prokaryotes lack a nucleus and membrane-bound organelles, have DNA in a nucleoid, and are usually smaller than eukaryotes.
  • What is the plasma membrane composed of?
    A double layer of phospholipids forming a selective barrier that regulates passage of oxygen, nutrients, and waste.
  • Why is the surface area to volume ratio important for cells?
    Smaller cells have a greater surface area to volume ratio, facilitating efficient diffusion of materials.
  • What is the function of the nucleus in eukaryotic cells?
    The nucleus stores most of the cell's DNA and genes, organizing DNA into chromosomes and controlling gene expression.
  • What are ribosomes and their role?
    Ribosomes are composed of rRNA and protein; they synthesize proteins using information from DNA.
  • What organelles are part of the endomembrane system?
    Includes nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane.
  • What are the two types of endoplasmic reticulum and their functions?
    Smooth ER synthesizes lipids, metabolizes carbohydrates, detoxifies poisons, and stores calcium ions; Rough ER has ribosomes and secretes proteins and glycoproteins.
  • What is the Golgi apparatus's role?
    Modifies products from the ER, manufactures macromolecules, produces glycolipids, and sorts/packages materials into vesicles.
  • What is the function of lysosomes?
    Lysosomes contain hydrolytic enzymes to digest macromolecules, participate in phagocytosis, and recycle cell components via autophagy.
  • What is the endosymbiont theory?
    Eukaryotic cells evolved when an ancestor engulfed oxygen-using prokaryotes (mitochondria) and photosynthetic prokaryotes (chloroplasts).
  • What are mitochondria and their function?
    Organelles in eukaryotic cells that perform cellular respiration to generate ATP, with a double membrane and their own DNA.
  • Describe chloroplast structure and function.
    Chloroplasts have inner and outer membranes, thylakoids stacked into grana, and stroma; they capture light energy for photosynthesis.
  • What are peroxisomes and their role?
    Membranous sacs containing enzymes that detoxify harmful substances and convert hydrogen peroxide into water and oxygen.
  • What is the cytoskeleton and its functions?
    A network of fibers (microtubules, microfilaments, intermediate filaments) that support cell shape, organize structures, and enable motility.
  • What are microtubules and their roles?
    Hollow rods made of tubulin that shape the cell, guide organelle movement, and separate chromosomes during cell division.
  • What are microfilaments and their functions?
    Thin rods of actin that bear tension, support cell shape, form microvilli cores, and enable muscle contraction.
  • What are intermediate filaments?
    Fibers with diameter between microtubules and microfilaments that reinforce cell shape and fix organelles in place, more permanent than others.
  • What is the plant cell wall composed of and its function?
    Made of cellulose microfibrils embedded in polysaccharides and proteins; it protects the cell, maintains shape, and prevents excess water uptake.
  • What is the extracellular matrix (ECM) in animal cells?
    A network outside the plasma membrane made of glycoproteins like collagen and fibronectin that bind cells and facilitate communication.
  • What are cell junctions and their types?
    Structures that connect neighboring cells: plasmodesmata in plants; tight junctions, desmosomes, and gap junctions in animals.