Microscopy Overview and Techniques

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Questions and Answers

What is the function of the ocular lens in a compound light microscope?

It is responsible for the resolving power.

It magnifies by 20x.

It magnifies by 10x. (correct)

It serves as the lens closest to the specimen.

Which of the following is true regarding the resolution in microscopy?

Resolution allows us to distinguish two points that are closer together. (correct)

Resolution is not affected by the wavelength of light used.

Resolution decreases with shorter wavelengths.

Higher resolution means the ability to see at greater distances.

How is total magnification calculated in a compound microscope?

Ocular lens / Objective lens

Objective lens + Ocular lens

Ocular lens x Objective lens (correct)

Ocular lens + Objective lens - 1

What is a characteristic of an electron microscope compared to a light microscope?

Allows greater magnification, up to 500,000x. Signup and view all the answers

What type of electron microscope is used for examining internal structures of a specimen?

Transmission Electron Microscope (TEM) Signup and view all the answers

Which statement about light and resolution is accurate?

Resolution requires light to pass between two objects. Signup and view all the answers

What is the resolving power of a microscope if two points can be distinguished as long as they are at least 4 nm apart?

4 nm Signup and view all the answers

Why do samples prepared for a TEM often require staining with metal?

To enhance the contrast of internal structures. Signup and view all the answers

What defines a prokaryote?

Lacks membrane-enclosed organelles. Signup and view all the answers

Which shape describes a bacterium that is corkscrew-shaped?

Spirochete Signup and view all the answers

What is the function of capsules in bacteria like Streptococcus pneumoniae?

Protect against phagocytosis. Signup and view all the answers

What distinguishes a slime layer from a capsule in bacteria?

Capsules are organized and firmly attached to the cell wall. Signup and view all the answers

Which of the following eukaryotic organisms is classified as multicellular?

Fungi Signup and view all the answers

What type of organism typically possesses a single circular chromosome?

Archaea Signup and view all the answers

How do slime layers aid bacteria like Streptococcus mutans?

They promote biofilm formation. Signup and view all the answers

What is the primary characteristic of eukaryotes?

Have membrane-enclosed organelles. Signup and view all the answers

Which of the following is a characteristic feature of eukaryotic cells?

Presence of membrane-bound organelles Signup and view all the answers

What component of the cytoplasmic membrane provides rigidity compared to bacterial membranes?

Sterols Signup and view all the answers

Which type of eukaryotic cell wall component is found in fungi?

Chitin Signup and view all the answers

What is the primary function of mitochondria in eukaryotic cells?

Energy production Signup and view all the answers

What structural feature distinguishes eukaryotic ribosomes from prokaryotic ribosomes?

Size and weight Signup and view all the answers

What is the primary function of the bacterial cell wall?

To prevent rupture and protect against environmental changes Signup and view all the answers

Which of the following is NOT a function of the cytoskeleton in eukaryotic cells?

Protecting against pathogens Signup and view all the answers

Which of the following eukaryotic organelles is responsible for photosynthesis?

Chloroplasts Signup and view all the answers

Which macromolecule primarily composes the bacterial cell wall?

Peptidoglycan Signup and view all the answers

What function do flagella and cilia serve in eukaryotic cells?

Movement and motility Signup and view all the answers

Which of the following statements accurately describes Gram positive bacteria?

They have a thick peptidoglycan layer and only one membrane. Signup and view all the answers

What characterizes the outer membrane in Gram negative bacteria?

It is made of lipopolysaccharides, proteins, and lipids. Signup and view all the answers

What are the alternating monosaccharides that make up the polysaccharide portion of peptidoglycan?

N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM) Signup and view all the answers

What type of acids are found in Gram positive bacteria that are not present in Gram negative bacteria?

Teichoic acids Signup and view all the answers

Which component of the Gram negative cell wall is known to be toxic?

Lipid portion of lipopolysaccharides Signup and view all the answers

What is a significant mechanism for distinguishing Gram negative bacteria such as E. coli?

The structure of their outer membrane and O-sugars Signup and view all the answers

What type of flagellar arrangement consists of a single polar flagellum?

Monotrichous Signup and view all the answers

Which of the following describes the motion produced by flagella when they turn in one direction?

Run Signup and view all the answers

What is the primary purpose of fimbriae in bacteria?

Adhesion to surfaces Signup and view all the answers

In which flagellar arrangement do tufts of flagella originate from opposite poles?

Amphitrichous Signup and view all the answers

Which statement accurately describes chemotaxis in bacteria?

It involves movement toward attractants and away from repellents. Signup and view all the answers

What is the function of pili in bacteria?

Genetic material transfer Signup and view all the answers

Which type of bacteria arrangement has flagella distributed all over the cell surface?

Peritrichous Signup and view all the answers

Which of the following best describes the structure of a flagellum?

Semi-rigid and helical Signup and view all the answers

Study Notes

Microscopy

Light Microscope: Visible light is used to observe specimens
- Compound light microscope: A type of light microscope that uses two lenses to magnify:
  - Ocular lens (Eyepiece): Magnifies by 10x.
  - Objective lens: Magnifies between 10x - 100x
Total magnification: Ocular lens x Objective lens
Resolution: Ability to distinguish fine detail.
- Determined by the wavelength of light used, shorter wavelength, better resolution.
Electron Microscope: Uses electrons for viewing, higher resolution, higher magnification
- Electron wavelengths are much shorter than light.
- Magnification is much greater with this method (up to 500,000x).
- Allows us to view viruses and internal cellular structures.
Types of Electron Microscope:
- Transmission Electron Microscope (TEM): For visualizing internal structures, thin slices of the sample are required.
Prokaryotes:
- "Before nucleus," DNA is not enclosed in a nucleus.
- Usually have one circular chromosome.
- Lack membrane-enclosed organelles.
- Examples: Bacteria, Archaea.
Eukaryotes:
- "True nucleus," DNA is located in the nucleus, surrounded by a nuclear membrane.
- DNA is arranged in multiple chromosomes.
- Contain membrane-enclosed organelles.
- Examples: Algae, Protozoa, Fungi, Plants, Animals.

Bacterial Morphology

Coccus: Spherical shape (plural: Cocci)
Bacillus: Rod-shaped (plural: Bacilli)
Vibrio: Curved shape
Spirillum: Spiral shape (plural: Spirilla)
Spirochete: Corkscrew shape.

Bacterial Cell Structure

Capsule: Sticky gelatinous layer outside the cell, aids in protection from phagocytosis.
- Examples: Streptococcus pneumoniae can cause disease when encapsulated, but not when lacking a capsule.
Slime layer: Unorganised and loosely attached, allows for surface adhesion.
- Example: Streptococcus mutans can make polysaccharide slime from sucrose and attach to teeth, contributing to cavities.
Flagella: Long protein appendages used for motility.
- Monotrichous: Single polar flagellum.
- Lophotrichous: Two or more flagella originating from one pole.
- Amphitrichous: Tufts of flagella originating from opposite poles.
- Peritrichous: Flagella distributed all over the cell.
Fimbriae: Short hair-like appendages that allow the cells to adhere to surfaces.
- They contribute to pathogenicity.
- Example: Certain strains of E. coli can attach to the intestinal wall with fimbriae.
Pili: Allows attachment of two bacteria to each other, involved in genetic material transfer.
- Example: E. coli sex pilus facilitates genetic exchange between bacteria.
Cell wall: Rigid structure defining the cell shape, prevents cell rupture, and protects from environmental changes.
- Composed of peptidoglycan.
- Used for bacterial identification.
- Peptidoglycan: Composed of polysaccharide and amino acid chains, forming a mesh-like structure around the cell.
Gram positive cell wall: Thick layer of peptidoglycan outside the plasma membrane.
- Contains teichoic acids:
  - Wall teichoic acids: Attached to the peptidoglycan.
  - Lipoteichoic acids: Attached to the plasma membrane and extend through the peptidoglycan.
- Has only one membrane - the cytoplasmic membrane.
Gram negative cell wall: Thin layer of peptidoglycan sandwiched between two membranes.
- Outer membrane composed of lipids (phospholipids), proteins, and lipopolysaccharides (LPS).
- LPS contains O-sugars used for identifying Gram-negative bacteria.
- The lipid portion of LPS is toxic and referred to as endotoxin.

Eukaryotic cell structure

Includes a wide range of microorganisms: Algae, Fungi, Protozoa
Larger and more complex than prokaryotes
Cells contain a defined nucleus
Contains membrane-bound organelles
Cytoplasmic membrane: Similar structure to prokaryotic cells, composed of phospholipids, proteins, and sterols.
- Sterols make the membrane more rigid compared to bacteria.
Cell wall: Not always present in eukaryotes, allows for endocytosis (taking in matter)
- Simple structure, but different composition depending on the type of cell.
- Made of cellulose (algae, plants), chitin (fungi).
Cytoplasm: The substance within the plasma membrane, outside of the nuclear membrane.
- Contains the cytoskeleton - protein filaments that provide support, shape, and facilitate transport in the cell.
Ribosomes: Larger and heavier than bacterial ribosomes (80S).
Membrane-bound organelles: Structures with specialized functions, not found in bacteria.
- Nucleus: Houses genetic material.
- Mitochondria: Site of energy production.
- Chloroplasts: Site of photosynthesis in algae and plant cells.
Flagellum and cilia: Long, flexible projections that contain protein and cytoplasm.
- Used for motility and sweeping material past stationary cells.
Endocytosis: Process of bringing external matter into the cell.
Exocytosis: Process of releasing matter from the cell.

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Description

Explore the fascinating world of microscopy with this quiz, covering various types of microscopes including light and electron microscopes. Understand concepts like total magnification, resolution, and the significance of different microscope types in cellular biology. Test your knowledge on how these tools help in studying microscopic structures.