Module 2 Foundations in Biology

• Light/Optical microscopes

  Have poor resolution due to the wavelength of light used to create the image, but can use living samples and produce color images
• Transmission electron microscopes

  Have much higher magnification and resolution, using electrons passing through the specimen to create the image
• Scanning electron microscopes

  Similar to transmission electron microscopes, but the electrons bounce off the surface to create a 3D image
• Laser scanning confocal microscopes

  High resolution and 3D, using laser light to create the image
• Resolution

  The minimum distance between two objects where they can still be viewed as separate
• Magnification

  How many times larger the image is compared to the actual object
• Slide preparation types

  • Dry mount
  • Wet mount
  • Squash slide
  • Smear slide
• Calibrating the eyepiece graticule

  1. Use a stage micrometer

  2. Align graticule and micrometer

  3. Count divisions on graticule that fit one division on micrometer

  4. Calculate value of one graticule division
• Magnification calculation

  Size of image / Size of real object
• Scientific drawings

  • Must be in pencil, include title and magnification, annotate structures, use solid lines with no shading or coloring
• Transmission electron microscopes

  Use a beam of electrons passing through a very thin, stained specimen in a vacuum to create a 2D image
• Scanning electron microscopes

  Use a beam of electrons bouncing off the surface of the specimen to create a 3D image
• Laser scanning confocal microscopes


  Use a high intensity laser to illuminate a fluorescently stained specimen, creating a 3D image by scanning through different focal planes
• Organelles in eukaryotic cells

  • Nucleus
  • Flagella
  • Cilia
  • Centrioles
  • Cytoskeleton
  • Endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Mitochondria
  • Peroxisomes
  • Plastids
  • Vacuoles
  • Ribosomes
• Nucleus

  • Contains DNA, site of DNA replication and transcription, has nuclear envelope with pores
• Flagella and cilia

  • Provide mobility and sensory functions
• Centrioles

  • Form the centrosome, involved in spindle fiber formation during cell division
• Cytoskeleton

  • Network of microfilaments, microtubules and intermediate fibers that provide mechanical strength and stability to the cell
• Endoplasmic reticulum

  • Rough ER is site of protein synthesis, smooth ER is site of lipid and carbohydrate synthesis
• Golgi apparatus

  • Modifies, packages and distributes proteins and other molecules produced in the ER
• Rough endoplasmic reticulum (RER)

  Site of protein synthesis because they have ribosomes on the outside, proteins can also be folded here
• Smooth endoplasmic reticulum (SER)

  Site of synthesis of lipids and carbohydrates, can also be used for storage
• Golgi apparatus

  • Folded membranes forming cisternae, vesicles bud off the edges, processes and packages proteins, creates lysosomes
• Lysosomes

  Vesicles containing digestive enzymes, can fuse with phagosomes to hydrolyze and destroy pathogens, break down dead cells
• Mitochondria

  • Double membrane-bound organelle, inner membrane folds to form cristae, site of aerobic respiration and ATP production, contains own ribosomes and DNA
• Ribosomes

  Small organelles made of protein and RNA, where protein synthesis occurs, 80S in eukaryotes, 70S in prokaryotes and organelles
• Chloroplasts

  • Double membrane-bound organelle found in plant cells, internal membrane folds form thylakoids and grana, site of photosynthesis
• Cell wall

  Provides structural strength, made of cellulose in plants, chitin in fungi
• Plasma membrane

  Phospholipid bilayer with embedded proteins, controls what enters and exits the cell
• Protein synthesis and secretion

  1. Polypeptide chains synthesized on RER ribosomes

  2. Polypeptides move to RER lumen and are folded/packaged

  3. Packaged into vesicles and transported to Golgi

  4. Proteins modified further in Golgi

  5. Packaged into secretory vesicles

  6. Vesicles fuse with cell membrane and release proteins by exocytosis
• Prokaryotic cells

  • Smaller, no membrane-bound organelles, circular DNA not in a nucleus, 70S ribosomes, cell wall made of murein, may have plasmids, capsule, flagella
• Biological molecules

  • Carbohydrates (C, H, O)
  • Lipids (C, H, O)
  • Proteins (C, H, O, N, sometimes S)
  • Nucleic acids (C, H, O, N, P)
• Water

  Polar molecule, forms hydrogen bonds, important as solvent, transport medium, coolant, habitat provider
• Monomer


  Smaller unit that can bind together to form a polymer
• Polymer

  Larger molecule made up of many monomers bonded together
• Monomers and polymers

  • Glucose (monomer) -> Starch, cellulose, glycogen (polymers)
  • Amino acids (monomers) -> Proteins (polymers)
  • Nucleotides (monomers) -> DNA, RNA (polymers)
• Alpha glucose, Beta glucose

  Structural isomers of glucose, differ in orientation of hydroxyl group on carbon 1
• Glycosidic bond

  Bond formed between two monosaccharides in a disaccharide during a condensation reaction
• Hexagon

  Each point represents a carbon atom, with additional carbon and hydrogen/hydroxyl groups
• Alpha glucose


  Hydroxyl and hydrogen on carbon 1 are on the same side of the ring