B3 Cells

• What is one method used for studying cells?

  Microscopes
• What are the two main types of microscopes?

  Light microscopes and electron microscopes
• What is the resolving power of light microscopes?

  0.2 µm
• Why is the resolution of light microscopes limited to 0.2 µm?

  Because it is the wavelength of light
• What is the resolving power of electron microscopes?

  0.1 nm
• How is magnification calculated in microscopy?

  Magnification = size of image / size of real object
• What does resolution define in microscopy?

  The minimum distance apart that two objects can be distinguished as separate
• What is the main limitation of light microscopes compared to electron microscopes?

  Light microscopes cannot resolve objects closer than 0.2 µm
• What is the function of the vacuum environment in electron microscopes?

  To prevent air particles from deflecting the electron beam
• How does a Transmission Electron Microscope (TEM) work?

  • A beam of electrons passes through a thin section of a specimen
  • Areas that absorb electrons appear darker on the micrograph
• How does a Scanning Electron Microscope (SEM) work?

  • A beam of electrons passes across the surface of a specimen
  • Scattering patterns build up a 3D image based on contours
• What is a limitation of using electron microscopes?

  Living specimens cannot be observed
• What is the purpose of the homogenate in cell fractionation?

  To separate different parts and organelles of a cell

  
• What are the steps of differential centrifugation in cell fractionation?

  1. Blend cells to form homogenate
  2. Spin at slow speed to sediment nuclei
  3. Remove supernatant and spin faster for mitochondria
  4. Continue increasing speed to separate other organelles

  
• Why is the homogenate placed in a cold, buffered solution?

  To slow down enzyme activity
• What type of cells are humans made up of?

  Eukaryotic cells
• What are the common features of eukaryotic cells?

  • Contain a nucleus
  • Have membrane-bound organelles
• What is the ultrastructure of the nucleus?

  • Double membrane called the envelope
  • Contains ~3000 nuclear pores
  • Contains chromatin and nucleolus
  • Nucleoplasm makes up the bulk
• What is the function of the Rough Endoplasmic Reticulum (RER)?

  • Folds and processes proteins made on ribosomes
• What is the function of the Smooth Endoplasmic Reticulum (SER)?

  • Produces and processes lipids
• What is the function of the Golgi apparatus?

  • Processes and packages proteins and lipids
  • Produces lysosomes
• What is the structure and function of mitochondria?

  • Oval-shaped, double membrane
  • Inner membrane folded into cristae
  • Contains enzymes for respiration
• What are the functions of centrioles?

  • Involved in producing spindle fibers for cell division
• What is the role of ribosomes in cells?

  • Site of protein production
• What are lysosomes and their function?

  • Vesicles containing digestive enzymes
  • Bound by a single membrane
• What structures do prokaryotic cells contain?

  • Cell wall made of peptidoglycan
  • Capsule for moisture retention
  • Plasmid (circular DNA)
  • Flagellum for movement
  • Pili for attachment
  • Ribosomes for protein production
  • Mesosomes for respiration

  
• What are viruses composed of?

  Nucleic acid enclosed in a protein coat
• How are cells organized in multicellular organisms?

  Cells into tissues, tissues into organs, organs into systems
• What is the role of mitosis in cell division?

  • Produces identical daughter cells
  • Important for growth, repair, and asexual reproduction
• What are the three stages of the cell cycle?

  1. Mitosis
  2. Interphase
  3. Cytokinesis

  
• What occurs during interphase?

  • Cell grows and prepares to divide
  • Chromosomes and organelles are replicated
  • Chromosomes begin to condense
• What happens during cytokinesis?

  • Parent and replicated organelles move apart
  • Cytoplasm divides to produce two daughter cells

  
• What is binary fission?

  The process by which prokaryotic cells divide
• What are the steps of binary fission in prokaryotic cells?

  1. Circular DNA replicates and attaches to the membrane
  2. Membrane grows and pinches inwards
  3. New cell wall forms between DNA molecules
• How do viruses replicate?

  Infected host cells replicate the virus particles
• What is the structure of biological membranes?

  • Composed of a sea of phospholipids
  • Contains protein molecules between phospholipids
  • Partially permeable membrane

  
• What is the main function of biological membranes?

  • Control movement of substances in and out of cells/organelles
  • Contains receptors for hormones
  • Enables adjacent cells to stick together
• What is the fluid mosaic model?

  • Describes the structure of the cell membrane
  • Fluidity of the membrane and mosaic arrangement of proteins
• What forms between the two DNA molecules during cell division?

  A new cell wall
• What do the identical daughter cells contain after cell division?

  A single copy of circular DNA and variable plasmid copies