2.1 Cell structure

• There are four different types of microscopes: light or Optical microscopes, transmission electron microscopes, scanning electron microscopes, and laser scanning confocal microscopes.
• Light or Optical microscopes have a poor resolution due to the wavelength of light and can be used on living samples to create a color image.
• Transmission electron microscopes have a higher magnification and resolution, with electrons passing through the specimen to create an image.
• Scanning electron microscopes are similar to transmission electron microscopes, but the electrons are bouncing off the surface to create a 3D image.
• Inside the Golgi apparatus, proteins are modified further and packaged into secretory vesicles which carry the proteins to the cell surface membrane.
• Prokaryotic cells are much smaller than eukaryotic cells, do not have membrane-bound organelles, have smaller ribosomes, circular DNA that is not contained within a nucleus and is not bound to histone proteins, and have cell walls made up of a molecule called murine.
• Some prokaryotic cells contain plasmids, a capsule, and a flagellum, but not all prokaryotic cells contain these three structures.
• Laser scanning confocal microscopes are high resolution and 3D, using laser light to create the image.
• Resolution in microscopy is the minimum distance between two objects in which you can still view them as separate, determined by the wavelength of the light in a light microscope or Optical microscope, and by the wavelength of an electron in an electron microscope.
• The eyepiece graticule is used to measure the size of the object being observed through a microscope.
• Different lenses on a microscope can cause different magnifications, such as times 10, times 40, or times 100.
• At each magnification, the value of one division on the eyepiece graticule will be different, and it must be calibrated at every magnification to determine its worth.
• A stage micrometer, which is a glass slide with a ruler on it, is used to calibrate the eyepiece graticule.
• The stage micrometer is placed on the stage of the microscope and aligned next to the eyepiece graticule.
• To calibrate the eyepiece graticule, the number of divisions on the eyepiece graticule that fit into one division on the stage micrometer is counted.
• On a stage micrometer, each division is worth 10 micrometers.
• Magnification in microscopy refers to how many times larger the images compared to the actual object that you are viewing, with four types of slide preparation in light microscopy: dry Mount, wet Mount, squash slide, and smooth Slide.
• Lysosomes can be created by the Golgi apparatus and are vesicles of digestive enzymes that contain lots of different enzymes with functions including the hydrolysis of bacteria, fusion with phagosomes in phagocytosis, and the complete breakdown of dead cells.
• Mitochondria are double membrane-bound organelles that contain their own ribosomes and loops of DNA, making them the site of aerobic respiration and ATP production.
• Ribosomes are small, made up of two subunits of protein and RNA, and are found in the cytoplasm of eukaryotic cells and in mitochondria and chloroplasts.
• Chloroplasts are found in plant cells and are the site of photosynthesis.
• Cell walls are found in plants and fungi of eukaryotic organisms, not in animal cells, and are made up of cellulose or chitin, providing structural strength.
• The plasma membrane is found in all cells and forms the cell surface membrane, made up of a phospholipid bilayer with other molecules embedded such as channel proteins, carrier proteins, proteins on the outside which might act as receptors, and cholesterol which affects the fluidity and therefore the permeability of the membrane.
• Dry Mount is when thin slices or even the whole organism or specimen are viewed, placed on top of a glass slide with a cover slip placed on top.
• Wet Mount is when the specimens are added to water or a stain before the cover slip is lowered on top with a mounted needle to prevent air bubbles forming.
• One division on the eyepiece graticule is worth 10 micrometers, allowing the size of the specimen to be calculated.
• The magnification calculation is the size of the image divided by the size of the real object.
• Staining is necessary to make some cell components visible under the microscope.
• Differential staining involves using multiple chemical stains to stain different parts of the cells different colors.
• Crystal violet and methylene blue are positively charged stains that are attracted to anything negative, including negatively charged components of the cell.
• Gram staining involves using two different stains to identify what type of bacteria you have.
• Gram-positive bacteria appear blue or purple as the stain is retained due to the really thick peptoglycan cell wall.
• Gram-negative bacteria cannot absorb Crystal Violet stain because their peptoglycan wool is thin, so they are stained with a counter stain, saffronin, which turns them red.
• Differential staining is important in determining which antibiotic would be best or most suitable to treat an infection.
• Scientific drawings are different from artistic drawings and have a complete set of rules, including using a sharp pencil, including a title, stating the magnification, and annotating the cell components or cells.
• Squash Mount is when a very thin slice from the tip of the root of an onion or garlic is placed on a glass slide, stained, and then squashed to create a thin layer of cells that the light can pass through.
• Smear Slide is created using the edge of another slide to smear your sample across your slide, then placing the cover slip on top.
• Inside a light microscope, the eyepiece has a scale that can be inserted on a glass disc and calibrated.
• Chromosomes are linear in shape and the nucleolus is a darker sphere inside the nucleus where RNA and ribosomes are created.
• The nucleolus is the site of ribosome synthesis.