Microbiology Chapter 3 Flashcards
The smallest virus is approximately ________ size of largest eukaryotic cell.
1/1,000,000th
The smaller size of prokaryotic cells gives high _______ to low ______. What does this allow?
Surface area; volume. Allows rapid growth.
What are the disadvantages of the high surface area to low volume ratio of prokaryotic cells?
Vulnerability to threats including predators, parasites, and competitors.
What are eukaryotic cells defined by?
Presence of a nucleus. Others include larger, more complex, and many cellular processes taking place inside membrane-bound compartments.
Which type of microscope can magnify 1,000x?
Light Microscope
Which type of microscope can magnify more than 100,000x?
Electron Microscope (1931)
Which type of microscope can produce images of individual atoms on a surface?
Scanning Probe Microscope (1980’s)
Which is the most common type of light microscope?
Bright-Field Microscope
What are the three key concepts of light microscopes? What are their definitions?
Magnification: Apparent increase in size.
Resolution: Resolving power, or ability to distinguish two objects that are very close together.
Contrast: Difference in color intensity between an object and the background, determines how easily cells can be seen.
What is the name for the eye piece of a light microscope? How much magnifying power does it offer?
Ocular Lens. 10x.
What is the magnifying piece that provides different magnifications to a light microscope?
Objective Lens.
What lens on a light microscope focuses the light?
Condenser Lens
What piece on a light microscope controls the amount of light that enters the objective lens?
Iris Diaphragm lever
What component of a light microscope controls the brightness of the light?
Rheostat
What is a Fluorescence Microscope used for?
Used to observe cells/materials either naturally fluorescent or tagged with fluorescent dyes.
What does epifluorescent mean?
UV light projected onto, not through, specimen.
Scientifically, how does a fluorescent microscope show specimen?
Molecules absorb light at one wavelength (usually UV) and emit light at longer wavelength. Most are epifluorescent.
How does an image under a Transmission Electron Microscope (TEM) differ than under other types of microscopes?
Depends on density of region; dark areas are more dense.
How is an image created using a Transmission Electron Microscope (TEM)?
Beam of electrons passes through the specimen or scatters.
What two methods reveal the shape of internal structures using a Transmission Electron Microscope?
Freeze-fracturing and freeze-etching.
What are two newer methods of Transmission Electron Microscope (TEM) that reduce damage to cells?
Cryo-electron microscopy and cryo-electron tomography.
How is an image created using a Scanning Electron Microscope (SEM)?
Beam of electrons scans over surface of specimen. Surface coated with a thin layer of metal.
What is unique about the image created using a Scanning Electron Microscope (SEM)?
Used to observe surface details. Yields 3-D effect.
What process uses a drop of liquid specimen overlaid with a cover slip?
Wet Mount
Wet mounts allow the observation of living organisms but can be difficult to see when the organisms are _______.
Colorless
For wet mounts, smear involves ______ and ______ specimen before _______ to visualize.
Drying; Fixing; Staining
Which type of staining uses a single dye to stain the specimen?
Simple Staining
Explain the science behind basic simple staining dyes. How does this compare to acidic simple staining dyes?
Basic dyes carry a positive charge, which is attracted to the negatively charged cellular components. Acidic dyes can be used for negative staining, in which cells repel the negatively charged dye so colorless cells stand out against background, can be done as wet mount.
What type of staining is used to distinguish different groups of bacteria? Which one is most widely used for bacteria?
Differential Staining; Gram Stain
What are the two groups of Gram-Staining? What does this difference reflect?
Gram-Negative and Gram-Positive Bacteria. Fundamental difference in cell wall structure.
Describe the steps of performing a gram stain.
Flood smear with primary stain. Rinse and flood with iodine to stabilize the dye in the cell. Rinse and add alcohol (decolorizing agent) to remove dye complex from gram-negative cells. Rinse and flood smear with counterstain that adds different color to gram-negative cells.
What is the name of spherical bacterial shape? What are the four arrangements in this shape?
Cocci.
Bunches; Chains; Quartets; Pairs.
What is the name of a stick/rod bacterial shape? What are the two arrangements for this shape?
Bacilli.
Alone; Chains.
What is the name for a “bent rod” bacterial shape?
Vibrios
What two bacterial shape categories are missing from the list below?
Cocci, Bacilli, Vibrios, _______, and ______.
Irregular; Spiral
What are the two most common bacterial shapes?
Coccus and Bacillus (Rod)
What is the name for a “short rod” shaped bacteria?
Coccobacillus
Bacterial shapes such as vibrios, spirillum, spirochete, and pleomorphic (many shapes) are often found in which environments?
Low nutrient environments
Most prokaryotes divide by what method?
Binary Fission
How are the characteristic groupings of cells formed?
Cells often stick together following division.
What is the fluid mosaic model?
Proteins drift about in lipid bilayer.
What cell component defines the boundary of the cell? _________ embedded with _______. _______ tails face in; ________ heads face out.
Cytoplasmic Membrane.
Phospholipid Bilayer; Proteins.
Hydrophobic; Hydrophilic.
What are three functions of proteins embedded within the cytoplasmic membrane?
Selective gates; Sensors of environmental conditions; Enzymes
The cytoplasmic membrane is _________.
Selectively Permeable
What are five substances that can pass freely through the cytoplasmic membrane?
O2, CO2, N2, small hydrophobic molecules, water.
Some cells use which structure to facilitate water passage?
Aquaporins
Movement from high to low concentration until equilibrium is reached describes which type of diffusion?
Simple Diffusion
During osmosis, water flows from ________ to _______ solution.
Hypotonic; Hypertonic
High water concentration; Low water concentration.
Low solute concentration; High solute concentration
What are two names of membrane-spanning transport systems that are used to transport molecules across the cytoplasmic membrane?
Permeates or Carriers
Transport systems are _______ to which types of molecules they carry across the cytoplasmic membrane.
Highly specific
Which type of diffusion is a form of passive transport?
Facilitated Diffusion
Facilitated Diffusion is not useful in what type of environment?
Low-Nutrient
Describe movement in facilitated diffusion. Does it require energy?
Movement down gradient; No energy required.
What type of transport requires energy?
Active Transport
What are the two driving methods for active transport with examples?
Proton Motive Force; Efflux Pump
ATP; ABC Transporter
What material is found only in bacteria, not archaea or eukaryotes?
Peptidoglycan
Describe the scientific makeup of peptidoglycan.
Alternating series of subunits (NAM and NAG) form glycan chains. Tetrapeptide chain links glycan chains.
Describe the peptidoglycan layer of a gram-positive cell wall. What materials are found above and below this layer?
Relatively thick peptidoglycan layer. Teichoic acids found above, gel-like material found below.
Describe the peptidoglycan layer of a gram-negative cell wall. What materials are found above and below this layer?
Thin peptidoglycan layer. Outside is unique outer membrane.
What is the name for the outer layer of the outer membrane of gram-negative cell walls?
Lipopolysaccharide (LPS)
What is another name for lipopolysaccharide (LPS)? Why is it called this?
Endotoxin. Large amounts accumulating in bloodstream can be deadly.
Lipopolysaccharide (LPS) is made up of what two components, besides polysaccharide. What are their functions?
Lipid A; Recognized by immune system.
O Antigen; Can be used to identify species or strains.
How does the outer membrane affect entry and exit of molecules in gram negative cells?
It blocks the passage of many molecules including certain antimicrobial medications. Small molecules and ions can still cross via porins.
What is located between the cytoplasmic membrane and outer membrane in gram negative cells?
Periplasmic space
What can be found in the periplasmic space?
Gel-like periplasm. Exported proteins accumulate unless specifically moved across outer membrane.
Why do antibacterial substances target the peptidoglycan layer?
Interference with peptidoglycan can weaken cell wall and allow cell to burst.
What are two elements that can interfere with peptidoglycan layer synthesis?
Penicillin and Lysozymes
How does penicillin interfere with peptidoglycan synthesis? How does its effectiveness vary for gram positive vs. gram negative bacteria?
Prevents cross linking of adjacent glycan chains. More effective against gram positive bacteria as the outer membrane of gram-negative bacteria blocks access.
How do lysozymes interfere with the peptidoglycan layer?
Breaks bonds linking glycan chains. Destroys structural integrity of peptidoglycan molecule. More effective against gram-positive.
What is lysozymes? Where are they found in our body?
Enzyme found in tears, saliva, and other body fluids.
What are capsules and slime layers in relation to bacteria? What is their benefit?
Gel-like layer outside cell wall protects or allows attachment. Some capsules allow bacteria to evade host immune system.
What is the difference between a capsule and a slime layer?
Capsule: Highly organized, tightly bound, offers mainly protection.
Slime layer: Less organized, loosely attached, aids in surface adhesion and biofilm formation.
What are most capsules and slime layers composed of?
Most composed of glycocalyx (sugar shell), but some are polypeptides.
Once attached to a surface, cells can grow as a ______. This is a _______-encased community.
Biofilm. Polymer.
What structure on bacteria is involved in motility?
Flagella
What is one case in which flagella is important in disease?
Helicobacter pylori.
What are the three parts of bacterial flagellum?
Basal body, hook, and filament.
What is the function of the basal body in flagellum?
Anchors to cell wall and cytoplasmic membrane.
What is the filament of a flagella made up of?
Made up of flagellin subunits.
How is an archael flagella different from a bacterial flagella?
Use energy from ATP instead of proton motive force.
Are pili shorter or longer than flagella?
Shorter
What is the name for a type of pili that allows surface attachment?
Fimbriae
What are two types of motility that are distinctly from pili?
Twitching and gliding.
What structure is used to join bacteria for a type of DNA transfer?
Sex Pilus
Describe the structure of the nucleoid in prokaryotic cells.
Chromosome forms gel-like region. Single circular double-stranded DNA molecule, packed tightly via binding proteins and supercoiling.
What type of information is encoded within plasmids?
Non-essential genetic information.
How does the structure of plasmids compare to chromosomes? How are they different?
Similar structure, just a lot smaller.
What is one result of plasmids being shared among bacteria?
Spread of antibiotic resistance.
T/F: Plasmids main function is to help bacteria overcome occasional stressful situations (I.E. resistant to antibiotics, digest unusual meal, kill other types of bacteria).
True
What structure is involved in protein synthesis? What is their job?
Ribosomes. Facilitate joining of amino acids.
How do the size of prokaryotic vs. eukaryotic ribosomes differ? (Expressed in terms of S).
Prokaryotic ribosomes are 70S (Composed of 50S and 30S subunit). Eukaryotic ribosomes are 80S.
How is the size of ribosomes important medically?
Antibiotics impacting 70S ribosome do not affect 80S ribosome.
Endospores can ________ to become __________ that can multiply.
Germinate. Vegetative cells.
What are endospores?
Unique type of dormant cell.
Who produces endospores?
Members of Bacillus, Clostridium.
How long can endospores remain dormant?
100 years or longer
Endospores are extremely resistant to what?
Heat, desiccation, chemicals, UV light, boiling water.
Where are endospores found?
Virtually everywhere.
What is the function of gas vesicles in prokaryotic cells?
Controlled to provide buoyancy.
_______ is the interior protein framework in prokaryotic cells.
Cytoskeleton
The cytoskeleton in prokaryotic cells is likely involved in ________ and _______?
Cell division. Controlling cell shape.
T/F: Bacterial proteins similar to the eukaryotic cytoskeleton have been characterized.
True
What are storage granules in prokaryotic cells? How are they synthesized?
Accumulations of polymers. Synthesized from nutrients available in excess.
What process with endospores is triggered by limited carbon or nitrogen?
Sporulation
Describe the steps of sporulation.
Starvation begins 8 hour process.
Endospore layers prevent damage (exclude molecules i.e. lysozymes).
Core maintained in dehydrated state, protects from heat.
Small proteins bind to and protect DNA.
Calcium plays an important role.
What process in endospores is triggered by heat and chemical exposure?
Germination
Formation of endospores is not a means of _________.
Reproduction
Cells within (eukaryotic) organisms vary. Similar cells form ______, various tissues form ______.
Tissues; organs.
Plant cells have a cell wall composed of _______.
Cellulose
Fungal cells have a cell wall composed of ______.
Polysaccharides such as chitin.
Protozoa and animal cells differ from fungal and plant cells through their lack of a _______.
Cell wall
Name the process: Cell takes up material from surrounding environment by forming invaginations in cytoplasmic membrane.
Endocytosis.
Name the process: Internal vesicles fuse with the cytoplasmic membrane and release their contents.
Exocytosis.
Pinocytosis is most common in which type of cell?
Animal cells
Describe the steps of pinocytosis.
Forms endosome, which fuses to lysosomes. Material degraded in endolysosome. Known as “cell drinking” as this process is used for absorbing fluids and solute.
_______________ allows cells to take up specific extracellular ligands that bind to surface receptors.
Receptor-mediated endocytosis.
Phagocytosis is used by what two groups to engulf?
Protozoa and Phagocytes (Immune Cell)
Describe the process of phagocytosis.
Psuedopods surround, bring material into phagosome. Phagosome fuses with lysosome to form phagolysosome where material is degraded. Known as “cell eating” because it involves the engulfment of larger particles.
What three components is the eukaryotic cytoskeleton made up of?
Actin Filaments, Microtubules, and Intermediate Filaments
What is the function of actin filaments, microtubules, and intermediate filaments in the cytoskeleton in eukaryotic cells?
Actin Filaments/Microfilaments: Allow movement
Microtubules: Thickest component. Framework for organelle and vesicle movement.
Intermediate filaments: Provide mechanical support.
Describe the structure of microtubules. What are they made of?
Long, hollow structures made of tubulin. Found in mitotic spindles, cilia, and flagella.
What are the two motility structures found in eukaryotic cells?
Flagella and Cilia
What covers the surface of flagella and cilia in eukaryotic cells?
Extensions of cytoplasmic membrane
What are flagella and cilia composed of in eukaryotic cells? What arrangement are they found in?
Microtubules in 9+2 arrangement.
How are eukaryotic flagella different from prokaryotic flagella?
Propel cell or pull it forward.
How do cilia compare to flagella in eukaryotic cells?
Cilia are shorter than flagella, move synchronously. Can move cell forward or more material past stationary cells.
What structure contains the genetic material in eukaryotic cells?
Nucleus
The nucleus in eukaryotic cells is surrounded by two ________.
Phospholipid bilayer membranes.
What structure allows molecules to pass in the nucleus of eukaryotic cells?
Nuclear Pores
What is the function of the nucleolus in eukaryotic cells?
Region where ribosome RNA’s synthesized.
What structure generates ATP in eukaryotic cells?
Mitochondria
The mitochondria is bound by _______ in eukaryotic cells.
two phospholipid bilayers
What are cristae in eukaryotic mitochondria and what is their function?
Inner membrane folds. Increases surface area for ATP generation.
The ____________ contains DNA and 70S ribosomes.
mitochondrial matrix
Where is photosynthesis performed in eukaryotic cells?
Chloroplasts
Chloroplasts are found in what two eukaryotic groups?
Plants and Algae
What is the function of chloroplasts in eukaryotic cells? How is this used?
Harvest sunlight energy to generate ATP. ATP used to convert CO2 to sugar and starch.
Chloroplasts have ____ membranes and contain ______ and _________.
Two
DNA; 70S ribosomes
What are the two major components located inside chloroplasts? What are they?
Stroma (Fluid-Filled Space) and Thylakoids (Stacked into grana, contain chlorophyll that captures radiant energy).
What is the theory that ancestors of mitochondria and chloroplasts were bacteria residing within other cells?
Endosymbiotic Theory
The endoplasmic reticulum is a system of _______, _______, and ______.
Flattened sheets, sacs, and tubes.
What is the function of the rough endoplasmic reticulum?
Dotted with ribosomes. Synthesize proteins not destined for cytoplasm.
What is the function of the smooth endoplasmic reticulum?
Lipid synthesis and degradation, calcium storage.
Describe the structure of the Golgi Apparatus.
Membrane-bound flattened compartments.
What is the function of the Golgi apparatus?
Macromolecules synthesized in the ER are modified (addition of carbohydrate, phosphate groups). Molecules sorted and delivered in vesicles.
What cellular organelle contains degradative enzymes that could destroy the cell if not contained?
Lysosomes
What two components fuse with lysosomes in separate cell processes?
Phagosomes and Endosomes
What is the name for the process in which old organelles and vesicles fuse with lysosomes?
Autophagy
What do peroxisomes use to degrade lipids and detoxify chemicals?
O2
What is the function of peroxisomes?
Degrades hydrogen peroxide, superoxide. Protects cell from the toxic effects of these molecules.
