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USMLE-Microbiology-basic bacteriology I

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colamember's version from 2016-12-07 18:00

Section 1

Question Answer
What is the function of peptidoglycan as a bacterial structure?give rigid support, protects against osmotic pressure
What is the chemical composition of peptidoglycan?sugar backbone with peptide side chains cross-linked by transpeptidase
What is the function of cell membrane (gram positives)?major surface antigen
What is the chemical composition of the cell membrane (gram positive)?peptidoglycan (support) and Lipoteichoic acid (induces TNF and IL-1, IL-6)
What is the function of outer membrane (gram negatives)?site of endotoxin (lipopolysaccharide (LPS)) and major surface antigen
What is the chemical composition of outer membrane (gram negatives)?Lipid A induces TNF and IL-1,
O polysaccharide is the antigen
What is the function of plasma membrane of the bacteria?site of oxidative and transport enzymes
What is the chemical composition of the plasma membrane?lipoprotein bilayer
What is the function of ribosome?protein synthesis
What is the chemical composition of a ribosome?50S and 30S subunits
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Section 2

Question Answer
what is the periplasm of the bacteria?space between the cytoplasmic membrane and outer membrane in gram-negative bacteria
What is the chemical composition of the periplasm?contains many hydrolytic enzymes, including B-lactamases (enzymes that break down B-lactam Abx: penicillin)
What is the function of the capsule of the bacteria?protect against phagocytosis

Firm: Capsule
Loose: (slime/biofilm); more resistance to Abx; more difficult to remove
What is the chemical composition of the capsule?polysaccharide (except Bacillus anthracis which contains D-glutamate)

Quelling test: tests for capsule;
(+) test = SWELLING
What is the function of the pilus/fimbria?mediate adherence of bacteria to cell surface; sex pilus forms attachment between 2 bacteria during conjugation
What is the chemical composition of the pilus/fimbria?glycoprotein
What is the function of a flagellum?motility
What is the chemical composition of a flagellum?protein
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Section 3

Question Answer
What is the function of a spore?resistant to dehydratation, heat and chemical
What is the chemical composition of a spore?keratin-like coat
dipicolinic acid
peptidoglycan
What is the function of a plasmid?PLASMID IS A VIRULENCE FACTOR;
contains a variety of genes for antibiotic resistance, enzymes and toxins
What is the chemical composition of a plasmid?DNA
Transferred from one org to another via CONJUGATION
What is the function of a glycocalyx ?mediates ADHERENCE to surfaces, especially foreign surfaces (e.g. indwelling catheter)
what is the chemical composition of a glycocalyx ?polysaccharide
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