Microbiology

🏥 Microbiology

Part 1 of 7 — Bacteria Structure & Function

Bacteria: prokaryotic, cell wall (peptidoglycan), no membrane-bound organelles.

Gram-positive: thick peptidoglycan, stains purple; Gram-negative: thin peptidoglycan + outer membrane, stains pink.

Concept Check 🎯

Key Insight: Bacterial shapes: cocci (spheres), bacilli (rods), spirilla (spirals).

MCAT Tip: Binary fission: asexual reproduction; doubling time can be as short as 20 minutes.

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Viruses & Prions

Part 2 of 7 — Viruses & Prions

Viruses: obligate intracellular parasites; DNA or RNA genome, protein capsid, some have envelope.

Lytic cycle: virus replicates immediately, lyses host cell; Lysogenic: integrates into host genome.

Concept Check 🎯

Key Insight: Retroviruses (HIV): RNA genome, reverse transcriptase makes DNA, integrates as provirus.

MCAT Tip: Prions: misfolded proteins that cause other proteins to misfold — no nucleic acid (e.g., CJD, mad cow).

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Fungi & Parasites

Part 3 of 7 — Fungi & Parasites

Fungi: eukaryotic, cell walls of chitin, heterotrophic, reproduce by spores.

Parasites: organisms that live on/in hosts; protozoa (single-celled) and helminths (worms).

Concept Check 🎯

Key Insight: Opportunistic infections: normally harmless microbes cause disease in immunocompromised hosts.

MCAT Tip: Symbiosis: mutualism (both benefit), commensalism (one benefits, other neutral), parasitism (one benefits, other harmed).

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Microbial Genetics

Part 4 of 7 — Microbial Genetics

Transformation: uptake of free DNA from environment; Transduction: DNA transfer via bacteriophage.

Conjugation: direct DNA transfer via pilus (F-plasmid); horizontal gene transfer.

Concept Check 🎯

Key Insight: Plasmids: extrachromosomal DNA, often carry antibiotic resistance genes.

MCAT Tip: Transposons: jumping genes that can move within and between genomes.

Concept Check 🎯

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Antimicrobial Agents

Part 5 of 7 — Antimicrobial Agents

Antibiotics: target cell wall (penicillin), protein synthesis (tetracycline), DNA replication (fluoroquinolones).

Antivirals: target viral entry, replication, or assembly (e.g., acyclovir, protease inhibitors).

Concept Check 🎯

Key Insight: Antibiotic resistance: mutation or acquired via horizontal gene transfer; a growing global threat.

MCAT Tip: Antiseptics (on living tissue) vs disinfectants (on surfaces) vs sterilization (complete elimination).

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Host-Pathogen Interactions

Part 6 of 7 — Host-Pathogen Interactions

Virulence factors: toxins (exotoxins, endotoxins), adhesins, capsule, biofilm.

Exotoxins: secreted proteins (botulism, cholera, diphtheria); Endotoxins: lipid A of Gram-negative outer membrane.

Concept Check 🎯

Key Insight: Koch postulates: criteria to establish a microorganism as the cause of a disease.

MCAT Tip: Immune evasion: antigenic variation, intracellular hiding, capsule to resist phagocytosis.

Concept Check 🎯

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Review & MCAT Practice

Part 7 of 7 — Review & MCAT Practice

Virulence factors: toxins (exotoxins, endotoxins), adhesins, capsule, biofilm.

Exotoxins: secreted proteins (botulism, cholera, diphtheria); Endotoxins: lipid A of Gram-negative outer membrane.

Concept Check 🎯

Key Insight: Koch postulates: criteria to establish a microorganism as the cause of a disease.

MCAT Tip: Immune evasion: antigenic variation, intracellular hiding, capsule to resist phagocytosis.

Concept Check 🎯

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