Unit 1 Biology: Viruses, Prokaryotes, and Eukaryotes Vocabulary

Vocabulary practice flashcards covering virus structures, replication cycles, cell theory, prokaryotic vs. eukaryotic features, endosymbiosis, bacterial morphology, Gram staining, and prokaryotic reproduction.

Virus

A non-living acellular structure containing nucleic acids (DNA or RNA, never both) surrounded by a protective protein coat.

Acellular

Not made of any cells.

Bacteriophage

A type of virus that specifically infects bacteria.

Capsid

The protective protein coating that surrounds the nucleic acids of a virus.

Protein Spikes

Specific glycoprotein structures (referred to as tail fibers in bacteriophages) on a virus that act as 'keys' allowing it to infect specific host cells.

Structure of Viruses

Viruses consist of nucleic acids surrounded by a capsid; some also feature an outer envelope, protein spikes, or specialized structures like a neck, sheath, and tail fibers.

Lytic Cycle

A viral replication pathway where the virus attaches, injects its nucleic acid, hijacks host cell machinery to produce viral components, assembles new viruses, and lyses (bursts) the host cell to release them.

Lysogenic Cycle

A viral replication pathway where viral DNA integrates into the host cell's chromosome as a prophage and replicates during cell division in a dormant state until an environmental trigger initiates the lytic cycle.

Prophage

Viral genetic information that has integrated itself into the host cell's DNA.

Vaccine

A preparation containing a less deadly or inactive virus introduced to prepare the body's immune system to fight a specific virus in the future without putting the body at risk.

Unicellular

An organism composed of a single cell, such as a bacterium.

Multicellular

An organism composed of multiple cells.

Prokaryotic Cell

A cell ranging between $1\text{--}10\text{ }\frac{1}{10^6}\text{m}$ ($1\text{--}10\text{ }\frac{1}{10^6}\text{m}$) in size with circular DNA, lacking a nucleus and membrane-bound organelles, reproducing via binary fission.

Eukaryotic Cell

A cell ranging between $100\text{--}1000\text{ }\frac{1}{10^6}\text{m}$ in size containing a nucleus with linear DNA and membrane-bound organelles, reproducing via cell division (mitosis).

Prokaryote vs. Eukaryote Structure

Eukaryotic cells store DNA inside a membrane-bound nucleus and contain organelles like mitochondria, while prokaryotic cells lack a nucleus, storing DNA in a nucleoid region.

Endosymbiosis

The evolutionary theory explaining that eukaryotic cells originated from a symbiotic relationship where an ancestral prokaryote engulfed smaller prokaryotes (such as aerobic or photosynthetic bacteria) that survived internally.

Prokaryotic Cell Structure

Prokaryotic cells always contain a cell membrane, cell wall, cytoplasm, ribosomes, and DNA, whereas structures like plasmids, flagella, capsules, and pili are only present in some.

Plasmid

An extra circular segment of DNA found in some prokaryotic cells.

Fimbriae

Hair-like projections on some prokaryotic cells used to attach to various surfaces.

Capsule

A protective layer surrounding the cell wall of some prokaryotic cells.

Conjugation Pilus

A specialized tube extended by a prokaryotic cell to transfer plasmid DNA to another cell during conjugation.

Coccus

A circular-shaped bacterial morphology.

Bacillus

A rod-shaped bacterial morphology.

Spirillum

A spiral-shaped bacterial morphology.

Diplo

A bacterial cell aggregation pattern consisting of pairs (groups of $2$).

Strepto

A bacterial cell aggregation pattern forming chains or lines.

Staphylo

A bacterial cell aggregation pattern forming clumps.

Archaea

A domain of prokaryotic organisms whose cell walls do not contain peptidoglycan.

Bacteria

A domain of prokaryotic organisms characterized by cell walls containing peptidoglycan.

Gram Staining

A staining procedure for bacteria using Crystal violet (purple) and Safranin (pink) dyes to differentiate cell wall peptidoglycan thickness.

Gram-Positive Bacterium

A bacterium with a thick peptidoglycan cell wall that retains Crystal violet dye, turning purple.

Gram-Negative Bacterium

A bacterium with a thin peptidoglycan cell wall and an extra outer membrane that retains Safranin dye, turning pink.

Heterotroph

An organism that obtains nutrients by absorbing or ingesting food.

Autotroph

An organism that produces its own food (e.g., photosynthetic organisms).

Obligate Aerobes

Organisms that can only survive in environments where oxygen is present.

Facultative Aerobes

Organisms that can survive in both oxygenated and oxygen-free environments.

Obligate Anaerobes

Organisms that can only survive in anaerobic environments with no oxygen.

Mesophiles

Organisms that live in moderate environmental conditions.

Thermophile

An extremophile organism that thrives in high-temperature environments.

Acidophile

An extremophile organism that thrives in acidic environments with low pH values.

Halophile

An extremophile organism that thrives in highly saline (salt-rich) environments.

Binary Fission

An asexual reproduction process in prokaryotes under favorable conditions, involving DNA replication, cell elongation, septum formation, and division into two identical daughter cells.

Conjugation

A process of transferring genetic material (such as plasmid DNA) between bacterial cells via a sex pilus under unfavorable conditions, which is not considered reproduction.

Endospores

Dormant, resistant structures formed by certain bacteria enabling them to survive extreme temperatures and lack of nutrients.