Science 10 – Unit C BIOLOGY Chapter 1 – The Microscope

C1.3 & C1.4 Development in imaging, staining, and cell research Cells inside the pulmonary artery of a cow

The quality of the image Three factors affect the quality of an image in microscopy: –magnification –contrast –resolution Skin cells of a frog

Magnification improved with advancements in lens- making light microscopes used in labs today can now magnify between X

Contrast refers to the variation of shadow and colour –it is contrast that allows the human eye to focus on different aspects of the image and to register depth cells by themselves are mostly colourless image quality has improved with: –new stains and staining techniques –new methods of illuminating the specimen

Contrast a cell with low contrast a cell with high contrast a cell with phase contrast illumination

Resolution the ability to distinguish between two structures that are very close together –the human eye is capable of resolving objects that are 0.1mm or larger the higher the resolution of a microscope, the more clearly you can see the magnified image similar to the resolution capabilities of a digital camera

Resolution the picture on the left has low resolution, and appears pixelated the picture on the right has a higher resolution and is therefore a clearer image

Fluorescent microscopy fluorescent stains called GFP (green fluorescent protein) are introduced to the specimen different cell structures absorb stains in different amounts the specimen is subjected to UV light depending on the type of dye, the cell glows either yellow, orange or green unlike conventional staining, GFP does not kill the cell, and allows for observation of living specimens

Brightfield microscopes light passes through the specimen fixing and staining process kills the specimen –you can’t view living tissues limited resoloution –you can’t get any higher resolution than 0.2µm

Confocal technology uses lasers and computers to focus the light the later reflects off the object and back to the eyepiece you see a thin section with high resolution computer software can be used to build up a 3D image fluorescent stains work better with confocal microscopes because they eliminate the blurriness of the reflected light

Confocal technology traditional optical microscope confocal microscope

Electron microscopy uses a fine beam of electrons instead of light the electrons pass through different materials at different rates, due to differences in density instead of lenses, EMs use magnetic fields to focus the image

Transmission Electron Microscope (TEM) electrons pass through the specimen 100X better magnification and resolution than light microscope difficult to produce 3D images specimens are fixed and stained, so living specimens cannot be observed

Scanning Electron Microscope (SEM) good for observing surface features of specimens –the specimen is fixed, and coated in gold –the electrons reflect off the gold and produce a 3D image –2X better image quality than the TEM uses computes to move the specimen and view it from different angles move the specimen and view it from different anglesmove the specimen and view it from different angles new SEMs permit the use of live material

Gene mapping with new imaging techniques comes new possibilities for research at the cellular level gene mapping refers to decoding of a species’ genome –an organism’s genome refers to all the information contained within its DNA in 2001, the Human Genome Project published a complete map of the entire human genome

Gene mapping could help us understand where cancer and other diseases come from and how to treat them more effectively also allows us to create new varieties of plants –ethical arguments arise about the dangers of genetically modified food

Cell communication cells are open systems, meaning they must interact with their environment to survive hormones are chemicals produced in one part of your body that act on a different part –for example, the hormone adrenaline is produced in your brain, but acts all over your body in times of stress or excitement –hormones and other transmitter chemicals form part of your cells’ communication system

Cell communication receptors on the surface of the cells allow transmitters to attach to the cell and carry out their function –only transmitters with the correct shape can dock at a particular receptor –similar to a lock and key method

Cell communication certain viruses and bacteria can trick the cells by mimicking the shape of a harmless molecule in order for your immune system to fight off invaders, it must first identify them, based on the markers on their cell membranes

Cell communication better understanding of cell communication allows scientists and research companies to: –diagnose diseases carried by viruses and bacteria –diagnose diseases of the immune system –make more targeted, and more effective medications

Homework Page 264 #1, Page 265 #10, 11 Complete the following table: Feature Light microscope Electron microscope illumination focused by how image is viewed advantages disadvantages