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University of Toronto Scarborough
Biological Sciences
Aarti Ashok

Cell Biology Lecture 1: Slide 19: Cells are alive: That’s because they can eat, and have a finite lifespan. They function alongside other cells, and are not isolated. Discoveries, which were later used for clinical application (No need to memorize them, since they will be used in later lectures. These informations are not in the slides): Claude and Palade: recognized the organization of cells Blobel: one of the most cited scientists; found signals in proteins to show where they go Fire and Mello: discovered the iRNA (interference RNA); now used for cancer research GFP (green fluorescent protein): used in cellular molecular studies Slide 28: Hooke: coined the word cell Leeywenhock: ‘father of biology’; noticed moving microbes in water, and labeled the bacteria in species categories Slide 31: Whole cells are not static. They move and transport materials both intracellular and intercellular, they assemble and disassemble and divide. Cells have receptors on their surface, which are used to interact with chemical signals (video, slide 31) Slide 33: Cells are self-regulated: they can repair themselves (ie. Can correct genetic errors), and can regulate cell division (they decide when to stop and start. That’s where cancer cells are an issue, since they stop that regulation and cells divide non-stop) Slide 35: Prokaryotes use binary fission, in which they just split in two without mitosis/meiosis) Slide 39: Fossil records have shown that prokaryotes came first around 2.7 billion years ago. Slide 41: Endosymbiotic cells 1) Anaerobic ancestor engulfed an aerobic prokaryote, thus becoming aerobic itself. 2) The aerobic prokaryote lives inside the cell and develops a membrane  mitochondria 5) The plant has engulfed an additional cyanobacteria, which evolved into the chloroplast. The cyanobacteria is one the most complex bacteria, because all of its membranes are capable of photosynthesis. Slide 44: A fertilized egg needs to divide and form around 250 different cells to become a multicellular organism (ie. Human) Slide 49: in vitro- outside body in a controlled environment (medium) Embryonic tissues stop after 50-100 divisions, so they are used in studies where you want to see how the subject authentically grows. Slide 51: Only one cell line is grown, which will be in a sterile environment to prevent contamination. They are then placed in an incubator where they divide. Slide 55: Mice kidney cell- confluent culture. The cells are closely spaced, and can’t divide anymore because of that. Microscope preparation: The cell is fixed by killing it first. However, the cell looks the same just as it was when it was alive. One block of the cell is cut off (around mm to micrometer sections). The blocks are stained for visibility, placed on the slide, and can be observed via microscope. (ex. Slide 58 Brain tissue) Slide 59: Other microscopes have different optics to look at different fractures of the cell. Increasing the contrast can make the cell more 3D (Fig. 18.6). Slide 61: The Electron Microscope: Electrons can be used as a light source, because they have very short wavelengths. You apply a voltage to get a wavelength, which gives a high resolution. The higher the wavelength, the poorer the resolution. Slide 63: electron microscope has a heated filament for electron source. It has a controlled voltage that accelerates the electrons, leading to a very short wavelength. Slide 64: Carbon, Oxygen and Hydrogen (which are found in all living organisms) are not electron dense, so when they are stained with heavy metal, the electrons scatter. Dark spots form where electrons scatter- like the nucleus. Ex Fig 18.11: the red blood cell is very condensed, and is full of prote
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