3.2.1.3 The method of studying cells Flashcards
Q: What are the three main types of microscopes used to study cells?
A: Optical microscopes, transmission electron microscopes (TEM), and scanning electron microscopes (SEM).
Q: What are the principles of optical microscopes?
A: Optical microscopes use visible light to magnify images of specimens, allowing for the observation of living cells.
Q: What are the limitations of optical microscopes?
A: Optical microscopes have a lower resolution compared to electron microscopes and cannot magnify images beyond a certain point (~1500x magnification).
Q: What are the principles of transmission electron microscopes (TEM)?
A: TEMs pass a beam of electrons through a thin section of the specimen, providing detailed images of the internal structure of cells
Q: What are the limitations of transmission electron microscopes (TEM)?
A: TEMs require the specimen to be in a vacuum, which means living cells cannot be observed. They also require extensive sample preparation and can only view very thin specimens.
Q: What are the principles of scanning electron microscopes (SEM)?
A: SEMs scan a focused beam of electrons across the surface of a specimen, producing detailed three-dimensional images of the specimen’s surface.
Q: What are the limitations of scanning electron microscopes (SEM)?
A: SEMs also require the specimen to be in a vacuum and cannot be used to observe living cells. Additionally, they only provide surface images, not internal structures.
Q: How do you measure the size of an object viewed with an optical microscope?
A: The size of an object can be measured using a calibrated eyepiece graticule or by applying the formula for magnification.
Q: What is the difference between magnification and resolution?
A: Magnification is how much larger an image appears compared to the real object, while resolution is the ability to distinguish two close points as separate.
Q: What is the formula for magnification?
A: Magnification = Size of Image / Size of Real Object.
Q: What are the principles of cell fractionation?
A: Cell fractionation involves breaking up cells to release their components, which can then be separated and studied individually.
Q: What is ultracentrifugation and how is it used in cell study?
A: Ultracentrifugation is a process where cell components are separated based on their size and density by spinning them at very high speeds in a centrifuge.
Q: Why was there a considerable period of time during which the scientific community was cautious about new methods of studying cells?
A: The scientific community takes time to validate and accept new techniques to ensure they provide accurate and reliable data.
