Viral Reproduction and Bacterial Colony Growth

Vocabulary flashcards covering viral replication mechanisms, entry pathways, lytic versus lysogenic cycles, retrovirus dynamics, binary fission, and the four phases of the bacterial growth curve.

Viral Replication Cycle

The multi-step process consisting of attachment, entry/penetration, uncoating, replication and protein synthesis (biosynthesis), assembly/maturation, and release by which a virus reproduces inside a host cell.

Bacteriophage

A complex-structured virus that infects bacterial host cells by attaching to the cell surface and injecting its viral DNA while its outer protein coat remains outside.

Endocytosis (Viral Entry)

A mechanism of viral entry in animal cells in which the host cell membrane folds around the virus to bring it inside within an endocytic vesicle.

Membrane Fusion (Viral Entry)

A mechanism of entry for enveloped animal viruses where the viral envelope fuses directly with the host cell membrane, releasing the viral capsid into the cytoplasm.

Vector

An organism, such as an aphid, that transmits infectious pathogens from one plant or host to another, often introducing the pathogen through damaged tissue.

Lytic Pathway

A destructive viral replication pathway where viral nucleic acids and proteins are actively synthesized, new virions are assembled, and the host cell bursts (lyses) to release thousands of viruses.

Lysogenic Pathway

A non-destructive viral cycle where viral DNA incorporates directly into the host genome, remaining latent and replicating along with the host chromosome without immediately destroying the cell.

Provirus

Viral DNA that has integrated into the host cell's DNA during the lysogenic cycle.

Latent Virus

An inactive virus residing inside a host cell whose genetic material is maintained without actively producing new virions or causing immediate disease symptoms.

Lysogeny

The state or period during which viral DNA remains incorporated and hidden inside host DNA while host cells continue dividing normally without symptoms.

Repressor Protein

A viral regulatory protein that blocks viral mRNA transcription and protein synthesis, maintaining the virus in a latent state during lysogeny.

Retrovirus

A specialized RNA virus, such as HIV or Rous Sarcoma Virus, that carries RNA as its genetic material and uses reverse transcriptase to synthesize DNA.

Reverse Transcriptase

A viral enzyme that catalyzes the transcription of viral RNA into double-stranded viral DNA.

Exocytosis (Viral)

The cellular transport process by which membrane-bound vesicles release newly assembled viruses outside the host cell without immediate destruction.

Cell Surface Receptor

A specific molecule or marker on the host cell membrane to which viral surface proteins or spikes must attach to initiate infection.

Plasmid

A small circular double-stranded DNA molecule found in bacteria that replicate independently of the bacterial chromosome.

HIV Structure

A retroviral structure characterized by an outer viral envelope embedded with glycoproteins, an inner protein capsid, viral RNA, and the enzyme reverse transcriptase.

Bacterial Colony

A visible mass containing millions of genetically identical or similar bacteria that originates from a single bacterium dividing repeatedly on solid nutrient media.

Binary Fission

A rapid, asexual reproductive mechanism in which a single bacterial cell replicates its circular chromosome, elongates, and divides into two genetically identical daughter cells.

Septum

The dividing wall formed by inward growth of the bacterial cell membrane and cell wall at the center of an elongated cell during binary fission.

Generation Time

The time required for one bacterial cell to divide into two cells, typically ranging from $20\text{--}30\,\text{minutes}$ under optimal conditions.

Bacterial Growth Curve

A graphical representation showing the logarithmic growth of a bacterial population over time through four characteristic phases: lag, exponential (log), stationary, and death.

Lag Phase

The initial period in a bacterial growth curve during which cells adapt to a new environment, synthesize enzymes, and increase metabolic activity with little to no cell division.

Log (Exponential) Phase

The period of maximum bacterial growth characterized by abundant nutrients, low waste accumulation, and rapid exponential binary fission.

Stationary Phase

The bacterial growth phase where the rate of new cell production equals the rate of bacterial death, causing the total population number to plateau due to nutrient limitation and waste accumulation.

Death (Decline) Phase

The final phase of bacterial culture growth where cell division largely ceases and the rate of cell death exceeds the rate of reproduction, resulting in an overall population decrease.