2.1.1 - cell ultrastructure and microscopes

Cards (65)

  • Magnification of a light microscope is x1500
  • light microscopes produce a 2D coloured image
  • Light microscopes are used to observe whole cells and tissues
  • Resolution is the ability to distinguish between very small separate structures very close together in great detail
  • TEMs have a resolution of 0.5nm
  • TEMs are used to look at organelle detail
  • TEMs produce a 2D black and white image
  • Scanning electron microscopes have a magnification of x100000
  • Scanning electron microscopes are used to see cell surface detail
  • Scanning electron microscopes produce a 3D black and white image
  • Laser scanning confocal microscopes produce a 3D coloured image
  • To prepare a temporary mount of tissue for a light microscope you:
    obtain a thin section of tissue; place tissue in a drop of water; stain tissue on a slide to make structures visible; add coverslip using mounted needle at 45 degrees.
  • TEMs work by passing a high energy beam of electrons through a thin slice of specimen; focus image onto a fluorescent screen; treat with heavy metal solution; more dense structures appear darker as they absorb more electrons.
  • An SEM works by focussing a beam of electrons onto a specimens surface using electromagnetic lenses; reflected electrons bounce off at different rates and produce a 3D image.
  • Laser scanning confocal microscopes work by focussing a laser beam onto a small area on the samples surface; specimen treated with fluorescent dye; sample emits protons and image is produced pixel by pixel in correct order.
  • Microscopic drawings are done with a sharp pencil and solid lines
  • Microscopic drawings include a scale bar and annotations of visible structures and how they appear on the microscope.
  • Magnification = image size / actual size
  • Differential staining is used to differenciate between cell types of different parts.
  • To calibrate microscopes place micrometer on stage, line up with the graticule.
    count how many divisions are in 100 eyepiece graticules.
  • If 100 eyepiece divisions = 60 micrometers
    Then 1 eyepiece division = 0.6 micrometers
  • 1 mm = 1000 micrometers
  • 1 micrometer = 1000nm
  • Include a title in microscopic drawings and ensure the proportions are correct
  • The nucleolus is dense and is made of RNA and proteins. It assembles ribosomes
  • Nucleus contains DNA coiled around chromatin which makes chromosomes
  • Nucleus controls cellular processes such as gene expression; specialisation; transcription and mitosis
  • Nuclear envelope separates nucleus from cell
  • Rough endoplasmic reticulum is a system of membranes containing fluid filled cavities - cisternae - that are continuous with the nuclear membrane
  • Rough endoplasmic reticulum is studded with ribosomes
  • Smooth endoplasmic reticulum is a system of membranes containing fluid filled cavities - cisternae
  • Smooth endoplasmic reticulum contains enzymes that catalyse reactions with lipid metabolism
  • Golgi apparatus is a stack of membrane bound flattened sacs. Cis face aligns with RER
  • Proteins are modified in the Golgi apparatus. molecules are added or its folded into a 3d shape
  • Ribosomes are small spherical organelles. There are 70s ribosomes in prokaryotic and 80s in eukaryotic cells.
  • Ribosomes, RER and Golgi apparatus are involved production of proteins.
  • For protein production:
    the ribosomes that synthesise proteins are attached to the RER.
    the Golgi apparatus aligns with RER
  • Mitochondria are surrounded by a double membrane. The inner membrane folds to form cristae. They have a fluid filled space - matrix - that contains mitochondrial DNA, enzymes, lipids and proteins. They can be spherical or rod shaped
  • Mitochondria are the site of aerobic respiration to produce ATP.
  • Chloroplasts are the site of photosynthesis to convert solar energy to chemical energy