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Questions and Answers
What is the primary function of a transmission electron microscope (TEM)?
What is the primary function of a transmission electron microscope (TEM)?
Which type of microscope is best suited for observing specimen in three dimensions?
Which type of microscope is best suited for observing specimen in three dimensions?
For what purpose is an inverted microscope primarily used?
For what purpose is an inverted microscope primarily used?
What role do fluorescent dyes (fluorochromes) play in fluorescence microscopy?
What role do fluorescent dyes (fluorochromes) play in fluorescence microscopy?
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What is a key characteristic of polarized microscopes?
What is a key characteristic of polarized microscopes?
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What is the primary source of illumination used in light microscopes?
What is the primary source of illumination used in light microscopes?
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What is the maximum theoretical magnification of a light microscope?
What is the maximum theoretical magnification of a light microscope?
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What type of radiation is used by electron microscopes?
What type of radiation is used by electron microscopes?
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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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Which of the following statements about light microscopes is incorrect?
Which of the following statements about light microscopes is incorrect?
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Study Notes
Introduction to Cytology and Genetics
- Cytology and genetics were introduced.
- Cell membrane, mitochondrion, cytoplasm, nucleus, DNA, endoplasmic reticulum, lysosome, ribosome, and Golgi apparatus are cellular components.
Microscopes
- Microscopes are optical devices used to observe microscopic objects (less than 70µm).
- The goal of the chapter is to explain microscope types, design, operation, and biomedical microscopic techniques.
Types of Microscopes
- Microscopes are categorized by the type of radiation used (light or electron).
Light Microscopes
- Light microscopes use white or UV light (sunlight, bulb, or vapor lamp).
- Optical components are made of glass.
- The resolution is 0.2 µm and maximum theoretical magnification is 2,000 times.
- Practical magnification is up to 1,000 times.
- Routine observation uses transmitted light.
- Fluorescent and inverted microscopes utilize light from above the slide.
Light Microscope Components
- The diagram displays microscope parts (eyepieces, observation tube, objective lens, stage, condenser lens, light source, base) and controls (neck, coaxial stage controls, course focus, fine focus, switch, rheostat).
Electron Microscopes
- Electron microscopes utilize a stream of electrons emitted by a cathode as radiation.
- Optical components use electromagnetic lenses.
- Resolution is 0.2 nm and maximum magnification is 1,000,000 times.
- Samples need preparation (fixation, staining, contrasting).
- Transmission electron microscope (TEM) visualizes samples by passing an electron beam through them.
- Scanning electron microscope (SEM) observes the sample surface with the electron beam.
Types of Electron Microscopes
- Transmission electron microscope (TEM) creates high-resolution images of internal cell structures by passing electrons through the sample.
- Scanning electron microscope (SEM) creates three-dimensional images of the specimen surface using a scanning electron beam.
Types of Light Microscopes
- Stereomicroscopes (dissecting microscopes) use light from two slightly different angles to view specimens in three dimensions.
- Low-power magnification is typically less than 100x.
Inverted Microscope
- This microscope type reverses the optical path, placing the optics below the slide and the light source above.
- It is useful for observing cell cultures growing on the bottom of Petri dishes.
Fluorescence Microscope
- For specific samples, a special type of light microscope uses UV (ultraviolet) radiation to illuminate the specimen, leading to light emission at longer wavelengths (visible light).
- Special fluorescent dyes, called fluorochromes, are used in this type of observation.
- The fluorescence microscopy is a useful technique for cytogenetic analysis (like FISH)
Polarized Microscope
- A polarized microscope uses polarized light generated by special Nicol prisms to observe structures like chitin, and crystalline cell inclusions.
Recommended Procedure for Microscopic Observation
- Quadrants, concentric circles, and clock face orientations aid in identifying specimen positions within the microscope's field of view.
Types of Slide Preparations
- Impression preparations press a clean slide against a tissue surface, facilitating cell observation.
- Smear preparations spread a drop of a cellular suspension across a slide.
- Covered slides comprise a sample, supported by a cover slip.
Native Slides
- Used to detect physiological cell behaviors like movement, division, and ingestion, but not good for intracellular structure analysis.
- Phase and dark-field microscopy are often used for observations requiring higher detail.
Fixation
- Fixation halts cellular processes and autolysis.
- Chemical or physical fixation methods are used, including heating and drying, and chemical solutions.
The Cell
- Cells are the functional and structural unit of all organisms.
- Cytology is the study of cells, including their basic life processes (metabolism, growth, reproduction, and irritability).
Cell Theory
- In 1838, Schleiden and Schwann defined plant and animal cells as elemental components of all living organisms.
- In 1855, Virchow revised the cell theory with the concept that all cells arise from existing cells.
Cell Types
- Prokaryotic cells (e.g., bacteria, archaea) are simple, small, and lack a nucleus or membrane-bound organelles.
- Eukaryotic cells (e.g., protozoa, fungi, plants, animals) are complex, larger, possess a nucleus, and have membrane-bound organelles.
Eukaryotic Cell
- Eukaryotic cells form unicellular or multicellular organisms.
- Organisms categorized by their nutritional pattern (autotrophic or heterotrophic).
- They undergo processes like differentiation to specialize.
Shape and Size of Cells
- Cell size and shape are specific to their locations and functions in the body.
- Cells exhibit various shapes like spherical, biconcave disc, squamous, cuboidal, polygonal, spindle-shaped, and multi-polar.
Cells According to Size
- Cells can be classified as small (e.g., erythrocytes, lymphocytes), medium-sized (e.g., plasma cells, chondrocytes), or large (e.g., human ova, megakaryocytes, motor neurons).
Molecular Structure of Cell Membranes
- Cell membranes (biomembranes) are essential components of all cells.
- Their discovery was closely tied to the development of transmission electron microscopy.
- Detailed observation reveals typical trilaminar structure.
- Chemical composition differences reflect cell specialization.
Function of Cell Membrane
- The cell membrane separates intracellular from extracellular spaces.
- It's a dynamic equilibrium boundary, maintaining the internal environment.
- It contains vital components like enzymes, receptors, and transport proteins, playing roles in substance intake and interactions.
Main Components of Cell Membranes
- Phospholipids are main cell membrane components, arranged in a double layer (bilayer).
- Polar heads face the aqueous environment, while non-polar tails face inward.
- These phospholipids are not chemically bound, therefore they can move laterally.
Cell Membrane Proteins
- Integral proteins penetrate or traverse the phospholipid bilayer.
- Peripheral proteins are situated on the surface of the bilayer.
- Proteins have various roles: transport of ions and substances, signal reception (hormones, neurotransmitters), and catalytic activity (enzymes).
Cell Junction Types
- Descriptions of cell junction types (tight junctions, adherens junctions, desmosomes, gap junctions) are included.
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Description
Explore the fundamentals of cytology and the various types of microscopes used in biology. This quiz covers key cellular components and provides an overview of light and electron microscopes, their functions, and design. Test your knowledge of microscope operation and biomedical techniques.
