Lecture Notes: Viruses, Prokaryotes, Eukaryotes & Fungi (Vocabulary Flashcards)

Vocabulary flashcards covering major concepts from the lecture notes on viruses, prokaryotes, eukaryotes & fungi.

Virus

A noncellular infectious agent with genetic material (DNA or RNA), a protein capsid, and sometimes a lipid envelope; it is an obligate intracellular parasite.

Capsid

Protein coat that surrounds and protects the viral genome.

Envelope

Lipid membrane surrounding some viruses, often derived from the host cell.

TMV (Tobacco Mosaic Virus)

One of the first viruses described; discovered by Dmitri Ivanovsky in 1892.

Dmitri Ivanovsky

Virologist who demonstrated the existence of a filterable infectious agent (TMV), foundational to virology.

Regressive hypothesis

Idea that viruses originated from degenerate cellular parasites.

Cellular origin (escape) hypothesis

Idea that viruses arose from genetic elements that escaped from host cells.

Virus-first (coevolution) hypothesis

Idea that viruses and cells coevolved, with viruses possibly predating cellular life.

Helical virus

Virus with a rod-shaped, helical capsid symmetry.

Icosahedral virus

Virus with a spherical, 20-faced icosahedral capsid.

Complex viral shape

Viruses with irregular or multipart shapes not strictly helical or icosahedral.

Infection steps

Sequence: attachment → entry → uncoating → replication → assembly → release.

Lytic cycle

Viral replication that bursts the host cell, releasing progeny virions.

Lysogenic cycle

Viral genome integrates into host DNA and remains dormant (prophage).

Endocytosis

Cellular uptake where the virus is engulfed in a vesicle.

Membrane fusion

Viral envelope fuses with the host cell membrane to release the genome.

Injection

Bacteriophages inject their genome into bacterial hosts.

Acute infection

Infection with rapid onset and short duration.

Persistent infection

Infection that persists for a long time, often lifelong.

Latent infection

Virus remains dormant and may reactivate later.

Oncogenic virus

Virus associated with cancer development.

Plant virus symptoms

Symptoms include stunted growth, mosaic leaves, spots, and yellowing.

Vaccine (inactivated)

Vaccine containing killed pathogens that cannot replicate.

Vaccine (attenuated)

Vaccine with live but weakened pathogens that replicate poorly.

Vaccine (subunit)

Vaccine using a fragment or component of the pathogen.

Antiviral

Drug or agent that inhibits viral replication or spread.

Prions

Infectious proteins (no nucleic acids); examples include mad cow disease.

Viroids

Short RNA pathogens that infect plants; do not encode proteins.

Stromatolites

Layered structures formed by ancient microbial communities; among the oldest fossils (~3.5 bya).

Extremophiles

Organisms thriving in extreme environmental conditions.

Thermophiles

Heat-loving microorganisms.

Halophiles

Salt-loving microorganisms.

Methanogens

Archaea that produce methane; anaerobic and oxygen-free.

Acidophiles

Organisms that thrive at acidic pH.

Alkaliphiles

Organisms that thrive at basic (alkaline) pH.

Mutation

Genetic change; a key mechanism for diversity in bacteria.

Transformation

Uptake of free DNA from the environment by bacteria.

Transduction

Gene transfer mediated by bacteriophages.

Conjugation

Direct transfer of DNA between bacteria through a pilus.

Biofilm

Surface-attached microbial community; stages: attachment, colonization, maturation, dispersion.

Nucleoid

Region in bacteria where the chromosome resides; lacks a true nucleus.

Gram-positive

Bacteria with a thick peptidoglycan layer; stains purple.

Gram-negative

Bacteria with a thin peptidoglycan layer and an outer membrane; stains pink.

Peptidoglycan

Polymeric layer forming bacterial cell walls; thickness differs between Gram types.

Phototroph

Organism that uses light as an energy source.

Chemotroph

Organism that uses chemical energy sources.

Autotroph

Organism that fixes CO2 as its carbon source.

Heterotroph

Organism that requires organic molecules for carbon and energy.

Producers

Organisms that synthesize organic matter (e.g., cyanobacteria, plants).

Consumers

Organisms that eat other organisms.

Decomposers

Organisms that recycle nutrients by breaking down organic matter.

Carbon cycle

Cycle involving photosynthesis, respiration, decomposition, and combustion.

Nitrogen cycle

Cycle with nitrogen fixation, nitrification, assimilation, and denitrification.

Endosymbiotic theory

Theory that mitochondria and chloroplasts originated from engulfed prokaryotes.

Mitochondria

Double-membrane organelles with cristae; contain own DNA/ribosomes; site of ATP production.

Protists

Eukaryotic, mostly unicellular organisms distinct from plants, animals, and fungi.

Protist metabolism (types)

Photoautotrophs, heterotrophs, and mixotrophs.

Protist motility

Movement via flagella, cilia, or pseudopodia.

Archaeplastida

Group including red and green algae and land plants.

SAR Clade

Grouping of protists: Stramenopiles, Alveolates, Rhizarians.

Stramenopiles

Diotoms, brown algae; often have silica-based structures.

Alveolates

Dinoflagellates, ciliates, and Plasmodium; have alveolar sacs.

Rhizarians

Forams and radiolarians with mineral skeletons.

Excavata

Group with diverse parasites; examples: Giardia, Euglena, Trypanosoma.

Amoebozoa

Amoeboid organisms and slime molds.

Opisthokonta

Clade containing animals, fungi, and choanoflagellates.

Plasmodium

Malaria-causing parasite; apicomplexan.

Trypanosoma

Parasite causing sleeping sickness; flagellated protist.

Giardia

Flagellated protist causing intestinal infections.

Entamoeba

Genus causing intestinal dysentery.

Phytophthora infestans

Oomycete plant pathogen responsible for potato blight.

Fungi

Eukaryotic, heterotrophic organisms that absorb nutrients by secreting enzymes.

Septate hyphae

Hyphae with cross walls (septa) between cells.

Coenocytic hyphae

Hyphae without septa; multinucleate.

Mycorrhizae

Symbiosis between fungi and plant roots improving nutrient uptake.

Lichens

Fungal-algal/cyanobacterial symbiosis; pioneers in soil formation and pollution sensitivity.

Chytridiomycota

Fungi with flagellated spores; chytrids; impact on amphibians.

Zygomycota

Fungi with coenocytic hyphae and zygospores (e.g., Rhizopus).

Glomeromycota

Fungi forming arbuscular mycorrhizae with plants.

Ascomycota

Sac fungi; includes yeasts, morels, and many molds.

Basidiomycota

Club fungi; include mushrooms, puffballs, rusts.