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Questions and Answers
What did Robert Hooke observe when he first discovered cells?
What did Robert Hooke observe when he first discovered cells?
What limitation did Antonie van Leeuwenhoek face despite his advancements?
What limitation did Antonie van Leeuwenhoek face despite his advancements?
Which scientist concluded that all plant tissues are composed of cells?
Which scientist concluded that all plant tissues are composed of cells?
According to the cell theory, which statement is NOT considered true?
According to the cell theory, which statement is NOT considered true?
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What is one key characteristic of living things mentioned?
What is one key characteristic of living things mentioned?
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Which limitation did Robert Hooke have with his microscope?
Which limitation did Robert Hooke have with his microscope?
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What is the maximum resolution power of a light microscope?
What is the maximum resolution power of a light microscope?
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Which component of the cell was discovered by Robert Brown?
Which component of the cell was discovered by Robert Brown?
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What discovery is Rudolf Virchow noted for in cell biology?
What discovery is Rudolf Virchow noted for in cell biology?
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Which type of microscope provides a three-dimensional view of the specimen's surface?
Which type of microscope provides a three-dimensional view of the specimen's surface?
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Why must specimens be dead when viewed using a transmission electron microscope (TEM)?
Why must specimens be dead when viewed using a transmission electron microscope (TEM)?
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What is a significant limitation of light microscopes regarding resolution?
What is a significant limitation of light microscopes regarding resolution?
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What must often be used to enhance contrast when observing specimens with a light microscope?
What must often be used to enhance contrast when observing specimens with a light microscope?
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What was one of the major advancements made by Max Knoll and Ernst Ruska?
What was one of the major advancements made by Max Knoll and Ernst Ruska?
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Which of the following is a disadvantage of the transmission electron microscope?
Which of the following is a disadvantage of the transmission electron microscope?
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What is the resolving power of an electron microscope?
What is the resolving power of an electron microscope?
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What is a primary advantage of using a scanning electron microscope (SEM)?
What is a primary advantage of using a scanning electron microscope (SEM)?
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Which statement accurately describes the process of homogenization in cell fractionation?
Which statement accurately describes the process of homogenization in cell fractionation?
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Why is the solution used during homogenization kept cold?
Why is the solution used during homogenization kept cold?
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During differential centrifugation, what happens to larger and denser particles?
During differential centrifugation, what happens to larger and denser particles?
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What is the function of the supernatant in the context of differential centrifugation?
What is the function of the supernatant in the context of differential centrifugation?
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What is the primary purpose of cell fractionation?
What is the primary purpose of cell fractionation?
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What determines the speed and duration of centrifugation in differential centrifugation?
What determines the speed and duration of centrifugation in differential centrifugation?
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Which characteristic makes ultracentrifuges unique compared to regular centrifuges?
Which characteristic makes ultracentrifuges unique compared to regular centrifuges?
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Which statement about modern cell theory is accurate?
Which statement about modern cell theory is accurate?
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What distinguishes eukaryotic cells from prokaryotic cells?
What distinguishes eukaryotic cells from prokaryotic cells?
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Which is a method used for studying cells?
Which is a method used for studying cells?
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What is the maximum practical magnification of a light microscope?
What is the maximum practical magnification of a light microscope?
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What does resolution in microscopy refer to?
What does resolution in microscopy refer to?
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What formula is used to calculate resolution in microscopy?
What formula is used to calculate resolution in microscopy?
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How does the wavelength of light affect resolution in microscopy?
How does the wavelength of light affect resolution in microscopy?
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What is the significance of the numerical aperture in microscopy?
What is the significance of the numerical aperture in microscopy?
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Study Notes
Cell Structure and Functions
- Cells are the basic unit of life.
- Biology is the study of life and living organisms.
- Living things exhibit characteristics, including an organized structure, requiring energy for existence, reproduction, growth, metabolism, response to stimuli, adaptation to the environment, movement, and respiration.
- Cells are made up of organelles.
Discovery of Cells
- 1665: Robert Hooke observed cork slices using a microscope and coined the term "cells". He only saw empty cell walls of dead plant tissue. His microscope could only magnify 30X.
- 1650-1700: Antonie van Leeuwenhoek improved microscopes, achieving magnification up to 300X and observed living cells (blood cells, sperm, bacteria, protozoa, algae). His microscopes had limitations in resolution.
- 1830: Robert Brown discovered the nucleus in cells.
- 1838: Matthias Schleiden concluded that all plant tissues were made of cells.
- 1839: Theodor Schwann concluded that all animal tissues are made of cells.
- 1855: Rudolf Virchow discovered that all cells come from pre-existing cells.
Cell Theory
- All organisms are composed of one or more cells.
- The cell is the basic unit of structure and function in all organisms.
- All cells arise from pre-existing cells.
Modern Cell Theory
- Cells are the basic units of life.
- All living things are made up of cells.
- New cells arise from pre-existing cells.
- Cells contain DNA, passed during cell division.
- All cells are similar in chemical composition and metabolic activity.
- All energy flow occurs within cells.
Cellular Organization
- Simple: Prokaryotes (bacteria, archaebacteria).
- Complex: Eukaryotes (plants, animals, fungi, algae, protozoa).
- Eukaryotes have membrane-bound organelles.
- Prokaryotes lack membrane-bound organelles.
The Study of Cells
- Microscopy: The use of microscopes to study cells (with both light and electron microscopes).
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Light Microscopy: Uses visible light to view specimens, provides magnification and resolution.
- Resolution is the minimum distance between two points that can still be perceived as separate points (measured in nanometers).
- Magnification is the measure of the enlargement of an image (using objective lenses and ocular lenses).
- A lower resolution implies the images will appear blurry.
- Smaller wavelengths of light provide enhanced resolution. Blue light is often used because its wavelength is shorter than other colors in the visible spectrum.
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Electron Microscopy: Uses beams of electrons, vastly increasing resolution.
- Transmission Electron Microscopy (TEM): Transmits electrons through thin tissue sections; produces 2-D images and uses a fluorescent screen or photographic plates (electron micrographs).
- Scanning Electron Microscopy (SEM): Scans the surface of a specimen, forming a 3-D view of its contours and surface features.
- The resolving power of a light microscope is about 200nm. The resolving power of an electron microscope is only about 0.2nm.
- Limitations of the light microscope: The resolving power is limited by the wavelength of light used, and hence, the light microscope can't resolve finer details.
- Limitations of the electron microscope: Specimens must be dead (for vacuum) and sample preparation can alter the tissue.
Cell Fractionation
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Homogenization: Mechanical disruption of cells to break the cell wall and plasma membrane, is carried out in a cold, isotonic, buffered solution.
- Cold temperatures help to reduce enzymatic activity to prevent cell damage.
- An isotonic solution prevents osmotic damage.
- A buffered solution helps maintain a stable pH.
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Differential Centrifugation: Homogenate is centrifuged at different speeds; cellular components are separated based on size and density.
- Larger and denser particles form pellets at lower speeds, lower centrifugal forces and shorter time duration.
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Description
Explore the fundamental concepts of cell structure and their functions in the living organism in this quiz. Learn about the historical discoveries of cells by scientists like Robert Hooke and Antonie van Leeuwenhoek. Test your knowledge on the characteristics and components of cells.
