First Aid USMLE STEP 1- Microbiology Exam Review A+ 2023

First Aid USMLE STEP 1- Microbiology Exam Review A+ 2023 Cell Wall Overall Picture - Compare *Gram (+) to Gram (-)* *Flagellum* on bacteria is composed of what? What is the function? - ANS-Composition: Proteins Function: motility *Pilus/Fimbria* on bacteria is composed of what? What is the function? - ANS-Composition: Glycoprotein Function: Mediate adherence of bacteria to cell surface, sex plus during conjugation. *Spore* formation is ONLY possible is what type of bacteria? Why is the formation of spores important/beneficial? What is the composition of a spore? - ANS-Gram Positive Only Function: Resistant to dehydration, heat, and chemicals. Composition: Keratin-like coat; dipicolinic acid; peptidoglycan. *Capsule* will be composed of what on bacteria? What is the benefit of a capsule? - ANS-Function: Protects against phagocytosis Composition: Organized, discrete polysaccharide layer (except Bacillus anthracis, which contains dglutamate) Glycocalyx - ANS-Function: Mediates adherance to surfaces, especially foreign surfaces (e.g., indwelling catheters) Composition:Loose network of polysaccharides Periplasm - ANS-Space between the cytoplasmic membrane and outer membrane in gram-negative bacteria (peptidoglycan in the middle) Gram Neg only Accumulates components exiting gram neg cells, including hydrolytic enzymes (β-lactamases) Outer membrane (gram negatives) - ANS-Gram Neg Only Function: 1. Endotoxin: Lipid A induces TNF and IL-1; O polysaccharide is antigenic 2. Most OMPs are antigenic Porins: transport across outer membrane CONTINUES...