NURS 3110 Study Guide - Midterm Guide: Gram-Positive Bacteria, Antigen, Teichoic Acid

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4 Feb 2017

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Clinical Science Exam 1 Study Questions
1. Describe the function of the following bacterial/prokaryotic cell structures: capsule,
cytoplasmic membrane, peptidoglycan layer, periplasmic space, fimbriae, glycocalyx, pili,
flagella. (See Microbiology, Chapter 4, pp 91-94)
o Protects cell from phagocytosis
Cytoplasmic membrane
o Structure: Phospholipids & Proteins
o Function:
Selective permeability & transport
Electron transport & oxidative phosphorylation
Excretion of some enzymes
Essential enzymes, carrier molecules
Receptors, proteins of chemotactic system
Peptidoglycan layer
o The cell walls of most bacteria gain their relative strength and stability
Periplasmic space
o Between inner & outer membrane
o Between cellular membrane and peptidoglycan layer
o 20-40% of cell volume
o Contains enzymes
o Aggregate and proliferate
o Small, bristlelike fibers emerging from the surface of many bacterial cells
o Develops as a coating of macromolecules to protect the cell and, in some cases, help
it adhere to its environment
o Rigid surface of protein
o Adherence to host
o Attachment of donor & recipient cells in bacteria conjugation (pass DNA)
o Allow for proliferation of organism
o Structure: Thread-like appendages of protein (H antigen)
o Organs of Motility
2. How does a gram-positive bacterial cell envelope differ from that of a gram-negative bacterial
cell envelope?
The Gram-Positive Cell Envelope
o Cytoplasmic membrane
o Thick peptidoglycan layer (cell wall)
o Some have outer capsule
o Outer layer of envelope and the size of that layer
o Does not have outer membrane
o More water solule
o Cytoplasmic membrane, thick peptidoglycan layer(responsible for retaining crystal
violet dyes during staining), may have a capsule
o Special components: teichoic acids(water soluble polymers and major surface
antigens) and polysaccharides
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The Gram-Negative Cell Envelope
o Cytoplasmic membrane (Cell membrane)
o Single sheet peptidoglycan
o Complex outer membrane layer (cell wall)
One layer
Then lipid layer
o May have outer capsule
Better able to live in hostile environments
Makes it easier to survive
o Endotoxins (lipopolysaccharide)**
Endotoxins if cell is lysed
If you kill cell and patient has infection, they are released and can be toxic to
Bacterial infectiontoxic
Makes gram negative dangerous
o More suitable for lipids because of phospholipid bilayer
Lipid soluble
o Naturally resistant to penicillin
o Outer membrane: protects cell from biles salts; special pores allow hydrophilic
compounds to pass
o LPS: endotoxin of gram neg; major surface antigen of bacteria; stabilizes outer
membrane; barrier to hydrophobic molecules
o Periplasmic space: between inner and outer membrane; contains enzymes
3. Why are each of the following media used by microbiologists? Enriched media, general-purpose
media, transport media, selective media, differential media (blood agar, chocolate agar). (See
Microbiology, Chapter 3)
Enriched media
o Contains complex organic substances such as blood, serum, hemoglobin, or special
growth factors that certain species must be provided in order to grow
o Organic compounds such as vitamins and amino acids that the microbes cannot
synthesize themselves
General purpose media
o Designed to grow a broad spectrum of microbes that do not have special growth
o Nonsynthetic (complex) and contain a mixture of nutrients that could support the
growth of a variety of bacteria and fungi
o Nutrient agar and broth, TSA
TSA is a complex medium that contains partially digested milk protein
(casein), soybean digest, NaCl, and agar
Transport media
o Used to maintain and preserve specimens that have to be held for a period of time
before clinical analysis or to sustain delicate species that die rapidly if not held under
stable conditions
o Contain buffers and absorbants to prevent cell destruction but will not support
Selective media
o Contains one or more agents that inhibit the growth of a certain microbe or microbes
but not another
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o This difference favors the one that it can’t inhibit and allows it to grow by itself
o Important in primary isolation of a specific type of microorganism from samples
containing mixtures of different species
Feces, saliva, skin, water, and soil
o Hasten isolation by suppressing the unwanted background organisms and allowing
growth of the desired ones
Differential media
o Blood sugar
o Chocolate agar
o Grow several types of microorganisms but are designed to bring out visible
differences among those microorganisms
o Differences show up as variations in colony size or color, in media color changes, or
in the formation of gas bubbles and precipitates
o These variations come from the types of chemicals contained in the media and the
ways that microbes react to them
o The simplest differential media show two reaction types such as the use or nonuse of
a particular nutrient or a color change in some colonies but not in others
o Several newer forms of differential media contain artificial substrates called
chromogens that release a wide variety of colors, each tied to a specific microbe
4. What is the significance of each of the following stages of bacterial growth? Lag phase,
stationary phase, exponential phase, decline phase. (See Microbiology, Chapter 7)
Lag phase
o Flat period on graph when population is not growing or is growing at a slow rate
Could be adjusting, population is sparse, or they are not multiplying at the
maximum yet
Stationary phase
o Survival mode where cells stop growing or grow slowly
o Rate of cell inhibition or death balances out the rate of multiplication
Exponential phase
o Infection proliferates quickly
o Maximum cell division
Decline phase (convalescent)
o Infection goes away
o Cells die at exponential rate and are unable to multiply
5. What environment is favored by each of the following? Aerobic bacteria, anaerobic bacteria,
facultative bacteria, microaerophilic bacteria.
Aerobic bacteria
o Most oxygen and some carbon dioxide
Anaerobic bacteria
o Can not grow in the presence of oxygen, oxygen is toxic for them
Facultative bacteria
o Versatile organisms, capable of growth under both aerobic and anaerobic conditions
Microaerophilic bacteria
o Low oxygen but not no oxygen
o Can grow in reduced oxygen and increased carbon dioxide
6. Compare and contrast the following terms: bacteriostatic, bacteriocidal
o Inhibits bacteria growth, can resume if conditions are right
Putting food in the fridge, urine, blood, stool
Inhibit additional proliferation, putting it back in room temperature
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