Bio112 Exam 2 Key Terms

Virus

A noncellular infectious particle composed of genetic material (DNA or RNA) enclosed in a protein coat and sometimes a lipid envelope.

Capsid

The protein shell that surrounds and protects a virus’s genetic material.

Capsomere

Protein subunits that make up a viral capsid.

Envelope (viral)

A lipid membrane surrounding some viruses, derived from the host cell membrane.

Bacteriophage

A virus that infects bacteria.

Host range

The limited range of host cells that a virus can infect.

Lytic cycle

Viral replication cycle resulting in host cell lysis and release of new viruses.

Lysogenic cycle

Viral replication cycle in which viral DNA integrates into the host genome and replicates with it without killing the host.

Prophage

Phage DNA that has been incorporated into the bacterial chromosome.

Attachment

The stage of viral replication where the virus binds to specific receptors on a host cell.

Penetration

The stage when a virus enters the host cell.

Uncoating

The process in which viral genetic material is released from the capsid inside the host cell.

Replication (viral)

The stage when viral nucleic acid and proteins are synthesized using host machinery.

Assembly

The stage when new viral particles are put together.

Release

The stage when new viruses exit the host cell (by lysis or budding).

Retrovirus

An RNA virus that uses reverse transcriptase to produce DNA from RNA.

Reverse transcriptase

An enzyme that synthesizes DNA from an RNA template.

Emerging virus

A virus that has recently increased in incidence or geographic range.

Zoonosis

A disease that can be transmitted from animals to humans.

Prion

An infectious misfolded protein that causes other proteins to misfold.

Viroid

A small infectious RNA molecule that infects plants.

Koch’s postulates

Four criteria used to establish that a specific microorganism causes a specific disease.

Prokaryote

A unicellular organism lacking a nucleus and membrane

Nucleoid

The region in a prokaryotic cell where DNA is located.

Plasmid

A small circular DNA molecule separate from chromosomal DNA.

Capsule (bacterial)

A sticky outer covering that protects bacteria and helps them adhere to surfaces.

Cell wall (prokaryotic)

A rigid structure outside the plasma membrane that maintains cell shape and prevents bursting.

Peptidoglycan

A polymer that forms the cell wall in bacteria.

Flagella

Long, whip

Fimbriae

Short hair

Binary fission

Asexual reproduction in prokaryotes where one cell divides into two identical cells.

Conjugation

Transfer of genetic material between bacteria through direct contact.

Transformation

Uptake of free DNA from the environment by a bacterial cell.

Transduction

Transfer of bacterial DNA by a bacteriophage.

Extremophile

An organism that thrives in extreme environmental conditions.

Thermophile

An extremophile that thrives at high temperatures.

Halophile

An extremophile that thrives in high salt concentrations.

Obligate anaerobe

An organism that cannot survive in the presence of oxygen.

Obligate aerobe

An organism that requires oxygen for survival.

Facultative anaerobe

An organism that can grow with or without oxygen.

Photoautotroph

An organism that uses light energy and carbon dioxide to make organic compounds.

Chemoautotroph

An organism that obtains energy from inorganic chemicals and uses CO₂ as a carbon source.

Heterotroph

An organism that obtains carbon from organic compounds.

Nitrogen fixation

The conversion of atmospheric nitrogen (N₂) into ammonia (NH₃).

Cyanobacteria

Photosynthetic prokaryotes that produce oxygen.

Proteobacteria

A major phylum of Gram

Gram

positive bacteria

Gram

negative bacteria

Pathogen

A disease

Antibiotic

A substance that kills or inhibits bacterial growth.

Vaccine

A biological preparation that stimulates immunity against a specific disease.

Antiviral drug

A medication that inhibits viral replication.

Herd immunity

Protection of a population from disease when a large percentage is immune.

Solubility product (Ksp)

The equilibrium constant for a solid dissolving into its ions.

Saturated solution

A solution containing the maximum amount of dissolved solute at equilibrium.

Crystallization

The process where dissolved ions form a solid crystal lattice.

Enthalpy (ΔH)

Heat change of a reaction at constant pressure.

Entropy (ΔS)

Measure of disorder or randomness.

Gibbs free energy (ΔG)

Energy available to do work; determines spontaneity.

Endothermic reaction

A reaction that absorbs heat (ΔH > 0).

Exothermic reaction

A reaction that releases heat (ΔH < 0).

Spontaneous process

A process that occurs without external energy input (ΔG < 0).

ΔG° =

RT lnK

Binary fission genetic variation

Variation produced by mutation, conjugation, transformation, and transduction.

Economic impact of viruses

Crop loss, livestock disease, healthcare costs, and productivity reduction caused by viral infections.

Lytic vs lysogenic difference

Lytic kills host immediately; lysogenic integrates into genome and remains dormant.