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Questions and Answers
What is the function of the ocular lens in a compound light microscope?
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?
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?
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?
What is a characteristic of an electron microscope compared to a light microscope?
What type of electron microscope is used for examining internal structures of a specimen?
What type of electron microscope is used for examining internal structures of a specimen?
Which statement about light and resolution is accurate?
Which statement about light and resolution is accurate?
What is the resolving power of a microscope if two points can be distinguished as long as they are at least 4 nm apart?
What is the resolving power of a microscope if two points can be distinguished as long as they are at least 4 nm apart?
Why do samples prepared for a TEM often require staining with metal?
Why do samples prepared for a TEM often require staining with metal?
What defines a prokaryote?
What defines a prokaryote?
Which shape describes a bacterium that is corkscrew-shaped?
Which shape describes a bacterium that is corkscrew-shaped?
What is the function of capsules in bacteria like Streptococcus pneumoniae?
What is the function of capsules in bacteria like Streptococcus pneumoniae?
What distinguishes a slime layer from a capsule in bacteria?
What distinguishes a slime layer from a capsule in bacteria?
Which of the following eukaryotic organisms is classified as multicellular?
Which of the following eukaryotic organisms is classified as multicellular?
What type of organism typically possesses a single circular chromosome?
What type of organism typically possesses a single circular chromosome?
How do slime layers aid bacteria like Streptococcus mutans?
How do slime layers aid bacteria like Streptococcus mutans?
What is the primary characteristic of eukaryotes?
What is the primary characteristic of eukaryotes?
Which of the following is a characteristic feature of eukaryotic cells?
Which of the following is a characteristic feature of eukaryotic cells?
What component of the cytoplasmic membrane provides rigidity compared to bacterial membranes?
What component of the cytoplasmic membrane provides rigidity compared to bacterial membranes?
Which type of eukaryotic cell wall component is found in fungi?
Which type of eukaryotic cell wall component is found in fungi?
What is the primary function of mitochondria in eukaryotic cells?
What is the primary function of mitochondria in eukaryotic cells?
What structural feature distinguishes eukaryotic ribosomes from prokaryotic ribosomes?
What structural feature distinguishes eukaryotic ribosomes from prokaryotic ribosomes?
What is the primary function of the bacterial cell wall?
What is the primary function of the bacterial cell wall?
Which of the following is NOT a function of the cytoskeleton in eukaryotic cells?
Which of the following is NOT a function of the cytoskeleton in eukaryotic cells?
Which of the following eukaryotic organelles is responsible for photosynthesis?
Which of the following eukaryotic organelles is responsible for photosynthesis?
Which macromolecule primarily composes the bacterial cell wall?
Which macromolecule primarily composes the bacterial cell wall?
What function do flagella and cilia serve in eukaryotic cells?
What function do flagella and cilia serve in eukaryotic cells?
Which of the following statements accurately describes Gram positive bacteria?
Which of the following statements accurately describes Gram positive bacteria?
What characterizes the outer membrane in Gram negative bacteria?
What characterizes the outer membrane in Gram negative bacteria?
What are the alternating monosaccharides that make up the polysaccharide portion of peptidoglycan?
What are the alternating monosaccharides that make up the polysaccharide portion of peptidoglycan?
What type of acids are found in Gram positive bacteria that are not present in Gram negative bacteria?
What type of acids are found in Gram positive bacteria that are not present in Gram negative bacteria?
Which component of the Gram negative cell wall is known to be toxic?
Which component of the Gram negative cell wall is known to be toxic?
What is a significant mechanism for distinguishing Gram negative bacteria such as E. coli?
What is a significant mechanism for distinguishing Gram negative bacteria such as E. coli?
What type of flagellar arrangement consists of a single polar flagellum?
What type of flagellar arrangement consists of a single polar flagellum?
Which of the following describes the motion produced by flagella when they turn in one direction?
Which of the following describes the motion produced by flagella when they turn in one direction?
What is the primary purpose of fimbriae in bacteria?
What is the primary purpose of fimbriae in bacteria?
In which flagellar arrangement do tufts of flagella originate from opposite poles?
In which flagellar arrangement do tufts of flagella originate from opposite poles?
Which statement accurately describes chemotaxis in bacteria?
Which statement accurately describes chemotaxis in bacteria?
What is the function of pili in bacteria?
What is the function of pili in bacteria?
Which type of bacteria arrangement has flagella distributed all over the cell surface?
Which type of bacteria arrangement has flagella distributed all over the cell surface?
Which of the following best describes the structure of a flagellum?
Which of the following best describes the structure of a flagellum?
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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
- Compound light microscope: A type of light microscope that uses two lenses to magnify:
- 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.
- Contains teichoic acids:
- 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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