MIC 102 Final Exam ACTUAL
QUESTIONS AND CORRECT ANSWERS
Light microscopy - CORRECT ANSWERS - Uses visible light to
examine microscopic-sized objects that cannot be seen by the naked eye.
- Allows finer detail than the naked eye.
Electron microscopy - CORRECT ANSWERS - Visualize objects much
smaller than those resolved optically.
- Use accelerated electrons instead of light photons.
- Samples are fixed with chemicals to cross-link molecules to preserve their
structure.
Fluorescent stains - CORRECT ANSWERS - Used with light
microscopy.
- Fluorescence is emitted from chemicals known as fluorochromes when
exposed to incident light of a shorter wavelength.
- Can visualize specific types of molecules.
- Specific to particular bacteria.
- Reacts or attaches to a molecule or receptor that reacts with desired cell target.
- The tags light up when excited by wavelength given off by fluorescent
microscope.
- Proteins can be tagged and tracked to see their localization.
- Green fluorescent protein (GFP): First fluorescent protein derived from a
jellyfish.
Gram stain - CORRECT ANSWERS - Developed by Christian Gram to
determine structures of bacteria using stains that contrasted their features.
- Can be distinguished by gram positive or gram negative bacteria.
,Gram positive stain - CORRECT ANSWERS - Stain with primary stain
(crystal violet).
- Add iodide which binds to crystal violet and traps it in cell.
- Rapidly wash with ethanol or acetone to decolorize, the violet will wash out.
- Counterstain with secondary stain, which will not retain.
- Stains purple because thick peptidoglycan wall that retains the crystal violet.
Gram negative stain - CORRECT ANSWERS - Stain with primary stain
(crystal violet).
- Add iodide which binds to crystal violet and traps it in cell.
- Rapidly wash with ethanol or acetone to decolorize, the violet will wash out.
- Counterstain with secondary stain.
- Stains red because it does not retain crystal violet and retains the secondary
stain.
Gram positive bacteria envelope - CORRECT ANSWERS - Contains
murein.
- Lacks outer membrane.
- Thick peptidoglycan cell wall -> enriches for polar molecules such as
phosphates, sugars, charged amino acids.
- Has teichoic acid: Provides rigidity and promotes stickiness of bacteria to
specific surfaces.
- Lipoteichoic acid: A type of teichoic acid that anchors to peptidoglycan cell
wall to cell membrane.
- Chemical feature: Contains LYSINE amino acid instead of DAP to crosslink
peptide chains with d-alanine residue (links the layers).
Gram negative bacteria envelope - CORRECT ANSWERS - Contains
murein.
- Thin peptidoglycan cell wall.
,- Has outer membrane that is resistant to harmful chemicals.
- Inner leaflet made of phospholipids.
- Outer leaflet made of lipopolysaccharide.
- Lipopolysaccharide makes up most of outer membrane, increases structural
integrity, aids in bacterial survival.
- Contains DAP
Murein - CORRECT ANSWERS - A peptidoglycan polymer consisting
of sugars and amino acids.
- Forms a mesh-like layer outside the plasma membrane of most bacteria, which
forms the cell wall.
Lipopolysaccharide - CORRECT ANSWERS - Large molecules
consisting of lipid and polysaccharide.
- Found in outer membrane of gram-negative bacteria.
- Makes up most of outer membrane and increases structural integrity.
- Aids in bacterial survival.
- Structural support, recognized by immune systems, filters hydrophobic
compounds, main reason for antigenic variety among gram negative bacteria.
Bacterial versus archaeal cell envelope - CORRECT ANSWERS -
Bacterial phospholipid bilayer has glycerol di-ESTERS (fatty acid chain).
- Archaeal phospholipid bilayers and monolayers have glycerol di-ETHERS
(isoprenoids).
Acid-fast envelope - CORRECT ANSWERS - Membrane glyocolipids
and long chain of fatty acids that are bound to peptidoglycan.
- Contains large amounts of waxes called mycolic acids.
- Do not have a full membrane.
, - Regular gram stains do not work because they cannot penetrate waxy layer.
Pros:
- Can protect against harsh chemicals, strong acids, antibiotics, and resist
phagocytosis.
Cons:
- Porins located in surface to allow nutrients in, but takes much longer.
- Cells are slow growing in binary fission due to tough outer shell.
Capsule - CORRECT ANSWERS - Slime is in one piece and remains
attached to cells.
- Polysaccharide layer that lies outside the cell envelope -> deemed to be part of
the outer envelope.
- Not easily washed off, can be the cause of various diseases.
- Prevents desiccation, exposure to chemicals, no biofilm.
Slime layer - CORRECT ANSWERS - Easily removable slime that is
unorganized and extracellular.
- High molecular weight polysaccharide, produced when environment demands
for it.
- Allows for retention of water, prevents diffusion of harsh chemicals, adhesion,
deters phagocytosis.
- Made of exopolysaccharides, glycoproteins, and glycolipids.
Function of capsules and slime layers - CORRECT ANSWERS - Cells
can synthesize these layers in response to environmental cues or due to their
cellular makeup.
- Retains water and nutrients, protects against dessiccation, limits diffusion of
harsh chemicals into cell.
QUESTIONS AND CORRECT ANSWERS
Light microscopy - CORRECT ANSWERS - Uses visible light to
examine microscopic-sized objects that cannot be seen by the naked eye.
- Allows finer detail than the naked eye.
Electron microscopy - CORRECT ANSWERS - Visualize objects much
smaller than those resolved optically.
- Use accelerated electrons instead of light photons.
- Samples are fixed with chemicals to cross-link molecules to preserve their
structure.
Fluorescent stains - CORRECT ANSWERS - Used with light
microscopy.
- Fluorescence is emitted from chemicals known as fluorochromes when
exposed to incident light of a shorter wavelength.
- Can visualize specific types of molecules.
- Specific to particular bacteria.
- Reacts or attaches to a molecule or receptor that reacts with desired cell target.
- The tags light up when excited by wavelength given off by fluorescent
microscope.
- Proteins can be tagged and tracked to see their localization.
- Green fluorescent protein (GFP): First fluorescent protein derived from a
jellyfish.
Gram stain - CORRECT ANSWERS - Developed by Christian Gram to
determine structures of bacteria using stains that contrasted their features.
- Can be distinguished by gram positive or gram negative bacteria.
,Gram positive stain - CORRECT ANSWERS - Stain with primary stain
(crystal violet).
- Add iodide which binds to crystal violet and traps it in cell.
- Rapidly wash with ethanol or acetone to decolorize, the violet will wash out.
- Counterstain with secondary stain, which will not retain.
- Stains purple because thick peptidoglycan wall that retains the crystal violet.
Gram negative stain - CORRECT ANSWERS - Stain with primary stain
(crystal violet).
- Add iodide which binds to crystal violet and traps it in cell.
- Rapidly wash with ethanol or acetone to decolorize, the violet will wash out.
- Counterstain with secondary stain.
- Stains red because it does not retain crystal violet and retains the secondary
stain.
Gram positive bacteria envelope - CORRECT ANSWERS - Contains
murein.
- Lacks outer membrane.
- Thick peptidoglycan cell wall -> enriches for polar molecules such as
phosphates, sugars, charged amino acids.
- Has teichoic acid: Provides rigidity and promotes stickiness of bacteria to
specific surfaces.
- Lipoteichoic acid: A type of teichoic acid that anchors to peptidoglycan cell
wall to cell membrane.
- Chemical feature: Contains LYSINE amino acid instead of DAP to crosslink
peptide chains with d-alanine residue (links the layers).
Gram negative bacteria envelope - CORRECT ANSWERS - Contains
murein.
- Thin peptidoglycan cell wall.
,- Has outer membrane that is resistant to harmful chemicals.
- Inner leaflet made of phospholipids.
- Outer leaflet made of lipopolysaccharide.
- Lipopolysaccharide makes up most of outer membrane, increases structural
integrity, aids in bacterial survival.
- Contains DAP
Murein - CORRECT ANSWERS - A peptidoglycan polymer consisting
of sugars and amino acids.
- Forms a mesh-like layer outside the plasma membrane of most bacteria, which
forms the cell wall.
Lipopolysaccharide - CORRECT ANSWERS - Large molecules
consisting of lipid and polysaccharide.
- Found in outer membrane of gram-negative bacteria.
- Makes up most of outer membrane and increases structural integrity.
- Aids in bacterial survival.
- Structural support, recognized by immune systems, filters hydrophobic
compounds, main reason for antigenic variety among gram negative bacteria.
Bacterial versus archaeal cell envelope - CORRECT ANSWERS -
Bacterial phospholipid bilayer has glycerol di-ESTERS (fatty acid chain).
- Archaeal phospholipid bilayers and monolayers have glycerol di-ETHERS
(isoprenoids).
Acid-fast envelope - CORRECT ANSWERS - Membrane glyocolipids
and long chain of fatty acids that are bound to peptidoglycan.
- Contains large amounts of waxes called mycolic acids.
- Do not have a full membrane.
, - Regular gram stains do not work because they cannot penetrate waxy layer.
Pros:
- Can protect against harsh chemicals, strong acids, antibiotics, and resist
phagocytosis.
Cons:
- Porins located in surface to allow nutrients in, but takes much longer.
- Cells are slow growing in binary fission due to tough outer shell.
Capsule - CORRECT ANSWERS - Slime is in one piece and remains
attached to cells.
- Polysaccharide layer that lies outside the cell envelope -> deemed to be part of
the outer envelope.
- Not easily washed off, can be the cause of various diseases.
- Prevents desiccation, exposure to chemicals, no biofilm.
Slime layer - CORRECT ANSWERS - Easily removable slime that is
unorganized and extracellular.
- High molecular weight polysaccharide, produced when environment demands
for it.
- Allows for retention of water, prevents diffusion of harsh chemicals, adhesion,
deters phagocytosis.
- Made of exopolysaccharides, glycoproteins, and glycolipids.
Function of capsules and slime layers - CORRECT ANSWERS - Cells
can synthesize these layers in response to environmental cues or due to their
cellular makeup.
- Retains water and nutrients, protects against dessiccation, limits diffusion of
harsh chemicals into cell.
