50 Questions
What is the basic unit of length in the metric system?
Nanometer (nm)
Which type of microscope can magnify objects in excess of 100,000x?
Electron Microscope
What physical phenomenon causes light rays to change direction due to a change in the medium through which they travel?
Refraction
What is the equivalent of 1 micron (µ) in meters?
10$^{-6}$ meter
What distinguishes major types of bacteria based on their cell wall characteristics?
Gram stain
Which type of bacteria has a unique lipid bilayer embedded with protein in its cell envelope?
Gram-negative
What stains the inside of the cell for Gram-positive bacteria in the Gram stain?
Crystal violet
Which type of bacteria requires the acid-fast stain due to its waxy coat?
Mycobacterium
What is the main component of the rigid cell wall found only in bacteria?
Peptidoglycan
What are the main components of peptidoglycan?
N-acetylmuramic acid and N-acetylglucosamine
In which type of cells are the glycan chains with peptide interbridges interconnected?
Gram-positive
What leads to the formation of long glycan strands with alternating NAM and NAG sugars?
Polymerization of subunits via their sugars
How many layers of glycan chains are present in Gram-positive cell walls?
As many as 30 layers
What are teichoic acids in Gram-positive cell walls composed of?
Negatively charged chains attached to sugars and D-alanine
Where are lipoteichoic acids linked in Gram-positive cells?
To the cytoplasmic membrane
What is the main advantage of electron microscopy in observing cell structures?
High magnification capability
Which staining method is used to distinguish between Gram-positive and Gram-negative bacteria?
Gram stain
What is the purpose of staining techniques in microscopy?
Improve contrast and visualize cells
Which staining method is used for microbes surrounded by a gel-like layer?
Capsule stain
What type of microscope is used to observe surface details by scanning a beam of electrons over the specimen?
Scanning Electron Microscope (SEM)
Why are staining methods necessary in microscopy?
Observing cells with a bright-field microscope is difficult due to cell transparency
Which staining method is used to detect organisms with high concentrations of mycolic acid?
Acid-fast stain
What is the main disadvantage of electron microscopy?
Complex specimen preparation
Which type of dye is attracted to negatively charged cellular components?
Basic dyes with a positive charge
What is the purpose of TEM in electron microscopy?
To observe fine details of cell structure by directing electrons that pass through or scatter
Which staining method is used for visualizing specific cell structures and proteins in microorganisms?
Immunofluorescence techniques
What is the most commonly used stain for bacteria?
Gram stain
What does resolution refer to in microscopy?
The ability to see objects as distinct, defined as the minimum distance at which two points can be distinguished as individuals
What is the resolving power of electron microscopes compared to bright-field microscopes?
Approximately 1,000 times greater
What is the purpose of immersion oil in bright-field microscopes?
To improve resolution
How is contrast in microscopy typically improved?
By staining cells with dyes or electron-dense materials
What is the function of dark-field microscopes?
To cause cells to stand out as bright against a dark background
What is the role of lenses in microscopy?
To focus light using refraction
What is the total magnification of a compound microscope with ocular lens of 10x and objective lens of 40x?
400x
What is the limit of the resolution of a bright-field microscope?
0.2µm
What does magnification refer to in microscopy?
The increase in the apparent size of the object compared to its actual size
What is the purpose of staining cells in microscopy?
To improve contrast
What is the purpose of using immersion oil in microscopy?
To improve resolution
What is the defining feature of dark-field microscopes?
Directing light towards the specimen at an angle, causing cells to stand out as bright against a dark background
What is the function of the cytoplasmic membrane in bacteria?
It acts as a critical permeability barrier between the cell and the external environment.
Which transport system allows substances to move across the membrane down the concentration gradient without requiring energy?
Facilitated diffusion
What are the structural features of bacteria?
Pilus, ribosomes, cytoplasm, chromosome (DNA), nucleoid, cell wall, flagellum, capsule, and cytoplasmic membrane.
What is the energy source for active transport in bacteria?
Proton motive force or ATP
Which type of bacteria is spherical in shape?
Coccus
What are the types of transport systems used by bacteria?
Facilitated diffusion, active transport, and group translocation
What is the function of protein secretion in bacteria?
Involves the active movement of proteins out of the cell
What are the two distinct types of bacteria mentioned in the text?
Staphylococcus aureus and Salmonella typhimurium
What is the selective permeability of the cytoplasmic membrane in bacteria?
Allows the passage of gases, water, and small hydrophobic molecules, but not sugars, ions, amino acids, or macromolecules.
What are the different shapes of bacteria mentioned in the text?
Coccus, rod (bacillus), vibrio, spirillum, and spirochete
What is the function of the pilus in bacteria?
Facilitates the transfer of genetic material between bacteria
Study Notes
Bacterial Shapes and Groupings
- Actin is represented in red, CEACAM in green, DNA in blue, and bacteria in cyan in the fluorescence microscope image from Anna Sintsova, Lab of Dr. Scott Gray-Owen, published in PLoS Pathogens (2014).
- Bacteria come in various shapes, with coccus being spherical and rod (bacillus) being cylindrical, ranging from 1 µm to 11.4 µm. Other shapes include vibrio, spirillum, and spirochete.
- Staphylococcus aureus and Salmonella typhimurium are two types of bacteria, each with distinct visual representations.
- Bacteria can form different groupings such as chains, packets (diplococcus), clusters, and long chains, each with specific characteristics.
- Structural features of bacteria include pilus, ribosomes, cytoplasm, chromosome (DNA), nucleoid, cell wall, flagellum, capsule, and cytoplasmic membrane.
- The cytoplasmic membrane is a thin, delicate membrane that surrounds the cytoplasm and acts as a critical permeability barrier between the cell and the external environment.
- The cytoplasmic membrane is selectively permeable, allowing the passage of gases, water, and small hydrophobic molecules, but not sugars, ions, amino acids, or macromolecules.
- Most molecules must pass through proteins functioning as selective gates, termed transport systems, to move nutrients, small molecules, waste, and other compounds across the cytoplasmic membrane.
- There are different types of transport systems, including facilitated diffusion, active transport using proton motive force or ATP, and group translocation.
- Facilitated diffusion is a form of passive transport that allows substances to move across the membrane down the concentration gradient without requiring energy.
- Active transport, which requires energy, can use proton motive force or ATP as an energy source to move substances against a concentration gradient.
- Protein secretion involves the active movement of proteins out of the cell, with proteins tagged for secretion via a signal sequence of amino acids, and various secretion systems used by prokaryotes.
Test your knowledge of bacterial shapes, groupings, and structural features with this quiz. Explore different bacterial shapes such as coccus, bacillus, vibrio, spirillum, and spirochete, and learn about bacterial groupings like chains, packets, and clusters. Delve into the structural features of bacteria, including the cytoplasmic membrane, pilus, ribosomes, cytoplasm, chromosome, nucleoid, cell wall, flagellum, and capsule. Gain insights into
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
