MCAT® ExamBiological and Biochemical Foundations of Living SystemsMedium
A scientist is investigating a newly discovered eukaryotic organism. Microscopic analysis reveals cells with a prominent nucleus, mitochondria, and a complex endomembrane system, but no cell wall or chloroplasts. Genetic analysis confirms the presence of genes coding for chitin synthesis. Based on these characteristics, which of the following is the most appropriate classification for this organism?
- APlant
- BFungus
- CProtist
- DAnimal
Show answer & explanationAnswer & explanation
Correct answer: B. Fungus
Eukaryotic cells with a nucleus, mitochondria, and endomembrane system, but lacking a cell wall composed of cellulose and chloroplasts, while possessing genes for chitin synthesis, are characteristic features of Fungi.
Why the other options are wrong
- A. Plants have cell walls (cellulose) and chloroplasts.
- C. Protists are a diverse group of eukaryotes; some have cell walls, some have chloroplasts, but the combination of no chloroplasts and chitin cell walls specifically points to fungi.
- D. Animals lack cell walls and chloroplasts, but do not synthesize chitin for structural purposes (though some animals like arthropods use chitin, it's not a general feature of animal cells).
Characteristics of Fungi
Fungi are a diverse kingdom of eukaryotic organisms that are heterotrophic, typically grow as filamentous structures (hyphae), and have cell walls made of chitin.
- Eukaryotic, with nucleus, mitochondria, and endomembrane system.
- Lack chloroplasts and are heterotrophic (absorptive feeders).
- Cell walls are composed of chitin.
- Reproduce via spores.
Memory trick: Eukaryotic 'FEATURES' classify the 'KINGDOMS'.