Study 10 flashcards on Classification, Morphology, Reproduction & General Properties with OmpathStudy. Quick, focused revision for Kenyan medical and health...
Q1. Classify fungi by sexual reproduction, giving the sexual spore and an example for each group.
Answer: Zygomycetes → zygospores (Rhizopus, Mucor) Ascomycetes → ascospores (Candida, Histoplasma) Basidiomycetes → basidiospores (Cryptococcus) Deuteromycetes → none; imperfect fungi (Aspergillus, Penicillium)
Q2. Describe the general properties of fungi.
Answer: Eukaryotic Chitin cell wall (not cellulose) No chlorophyll — cannot photosynthesize Chemoheterotrophic Ergosterols in membranes — key antifungal target 80S ribosomes Reproduce by spores Grow by budding or hyphal tip elongation Store glycogen and lipids Optimal pH ~5.0
Q3. Distinguish between septate and aseptate hyphae.
Answer: Septate — have cross walls (septa) with pores Cytoplasm flows freely; damage can be contained More evolved Aseptate — no septa; entire strand dies if damaged More primitive All moulds are septate EXCEPT Zygomycetes
Q4. Outline the beneficial effects of fungi.
Answer: Decomposition and nutrient/carbon recycling Fermentation → alcohols, fats, organic acids Antibiotics → Penicillin from Penicillium spp. Model organisms → Neurospora crassa, S. cerevisiae Food → mushrooms, vitamins, cofactors Cheese flavouring → Penicillium spp. Ergot alkaloids → uterine contractions, migraine treatment Biocontrol → trap mosquito larvae (malaria control)
Q5. Compare the three dermatophyte genera by macroconidia, microconidia and sites infected.
Answer: Microsporum → numerous, thick, rough macroconidia; rare microconidia; hair & skin Epidermophyton → smooth club-shaped macroconidia in clusters; NO microconidia; skin & nails Trichophyton → rare thin smooth macroconidia; abundant microconidia; hair, skin & nails
Q6. Describe dimorphic fungi — definition, temperature rule and examples.
Answer: Exist in two morphological forms depending on temperature Yeast form → at 37°C (body temperature / infected tissue) Mould form → at 25°C (room temperature / soil) Examples (mnemonic HBPC): Histoplasma capsulatum Blastomyces dermatitidis Paracoccidioides brasiliensis Coccidioides immitis
Q7. Distinguish yeasts, moulds, yeast-like fungi and dimorphic fungi morphologically.
Answer: Moulds → filamentous; made of hyphae forming a mycelium Yeasts → unicellular; spherical/ellipsoid; reproduce by budding Yeast-like → yeasts that produce pseudohyphae (e.g. Candida albicans) Dimorphic → yeast at 37°C; mould at 25°C
Q8. List and describe the types of asexual spores in fungi.
Answer: Conidia → formed at hyphal tips; micro or macroconidia (Aspergillus, dermatophytes) Sporangiospores → inside a sporangium on a sporangiophore (Rhizopus, Mucor) Arthrospores → from fragmented hyphae (Coccidioides immitis) Chlamydospores → thick-walled, resistant to harsh conditions (Candida albicans) Blastospores → formed by budding (yeasts)
Q9. What are the growth and nutritional requirements of fungi?
Answer: Optimal pH ~5.0 (acidic) Most grow at 25°C; pathogens grow at 37°C Aerobic — no obligate anaerobes Need water Grow well in high sugar concentrations Use glucose and maltose for energy Store glycogen Saprophytic (dead matter) or parasitic (living matter)
Q10. Outline the harmful effects of fungi.
Answer: Cause human and animal mycoses Produce mycotoxins and aflatoxins (carcinogens) Cause allergies Destroy lumber, paper and cloth Spoil stored agricultural produce Cause crop diseases e.g. potato blight Produce poisonous mushrooms e.g. Amanita spp.