OCR module 2 entire topic biology

• positves and negatives of Light/Optical microscopes


  Have poor resolution due to the wavelength of light used to create the image, but can use living samples and get colour images
• positives of 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
• what is Resolution?

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

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


  • Dry mount
  • Wet mount
  • Squash slide
  • Smear slide
• Eyepiece graticule


  A scale within the eyepiece of a microscope that can be used to measure the size of objects
• Calibrating the eyepiece graticule


  1. Align it with a stage micrometer

  2. Count how many eyepiece divisions fit into one stage micrometer division

  3. Use the known stage micrometer division value to calculate the eyepiece division value
• Magnification calculation


  Size of image / Size of real object
• Staining


  Adding dyes to make cell components more visible under the microscope
• Differential staining


  Using multiple stains to colour different cell components different colours
• Gram staining


  A differential staining technique used to identify whether bacteria are gram-positive or gram-negative
• Scientific drawings


  Accurate, labelled diagrams showing the size, shape, and location of structures, without any sketching, shading or colouring
• how do Transmission electron microscopeswork

  Use a beam of electrons that pass through a very thin specimen to create a 2D image
• how do Scanning electron microscopeswork?

  Use a beam of electrons that bounce 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
• Eukaryotic cell organelles


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

  animal, plant and fungal cells
• 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
• Endoplasmic reticulum (ER)


  • Smooth folded membranes
  • Rough membranes have ribosomes attached on the outside
• Golgi apparatus


  Folded membranes that form cisternae, vesicles bud off the edges, proteins are processed and packaged here, can modify proteins by adding carbohydrates, create secretory vesicles and lysosomes
• Lysosomes


  Vesicles containing digestive enzymes, can fuse with phagosomes to hydrolyze and destroy pathogens, involved in breaking down dead cells, contents released by fusing with cell membrane
• 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 ribosomes in eukaryotes, 70S ribosomes in prokaryotes and organelles like mitochondria
• Chloroplasts


  • Found in plant cells, double membrane, internal membrane folds called thylakoids stacked into grana, site of photosynthesis
• Cell wall


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


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


  1. Polypeptide chains synthesized on rough ER ribosomes

  2. Polypeptides move to ER lumen and are folded/packaged into vesicles

  3. Vesicles transported to Golgi apparatus for further modification

  4. Proteins packaged into secretory vesicles

  5. Secretory 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, some have plasmids, capsules, flagella
• Biological molecules


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


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


  Smaller units that can bind together to form polymers
• Polymers


  Larger molecules 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)
• Monosaccharides


  Single sugar units (e.g. glucose, fructose, galactose)
• Disaccharides


  Two monosaccharides bonded together (e.g. sucrose, maltose, lactose)
• Polysaccharides


  Many monosaccharides bonded together (e.g. starch, cellulose, glycogen)
• Alpha glucose


  One isomer of glucose, hydroxyl and hydrogen on carbon 1 are on the same side