Origins of Cells, Cell Structure, and Viruses Flashcards

A complete set of vocabulary flashcards based on lecture notes covering the origins of life, cellular structure and functions, microscopy developments, and viral dynamics.

Cell Theory

The fundamental biological theory stating that all living organisms are composed of cells and that all cells arise from pre-existing cells.

Stromatolite

A rocky mound structure formed by concentric layers of sediment and calcium carbonate laid down by cyanobacteria in shallow marine environments.

Hydrothermal Vent

A fissure in the ocean floor that releases superheated, mineral-rich water, considered a likely environment for the origin of early cellular life.

Organic Aerosol Haze

A hypothesized pre-biotic atmospheric condition where carbon compounds synthesized in water droplets were deposited into bodies of water by rainfall.

Theory of Spontaneous Generation

The disproved hypothesis stating that living organisms can arise spontaneously from non-living matter.

Miller-Urey Experiment

An experiment conducted in the early $1950\text{s}$ that simulated pre-biotic atmospheric conditions using electrical discharges, producing over $20$ different amino acids from simple inorganic gases.

Amphipathic

Describing a molecule that possesses both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions, such as a phospholipid.

Vesicle

A small fluid-filled droplet enclosed by a lipid membrane that can form spontaneously when amphipathic molecules are mixed with water.

Protocell

A self-assembled lipid membrane compartment containing self-replicating nucleic acids, used to model intermediate stages in the origin of cells.

Ribozyme

An RNA molecule capable of folding into complex three-dimensional structures that function as biological catalysts.

Codon

A specific triplet sequence of nucleotide bases in DNA or RNA that codes for a specific amino acid or translation stop/start signal.

Last Universal Common Ancestor (LUCA)

The most recent shared ancestral organism from which all currently living species on Earth originated.

Strelley Pool Formation

A rock formation in Western Australia containing uncontested fossilized stromatolites dating to $3.42\text{ Gya}$, providing a minimum age for early cellular life.

Inductive Reasoning

A logical methodology of developing general principles or scientific theories derived from specific empirical observations.

Resolution

The ability of an optical system or microscope to distinguish two close points as separate and distinct structures.

Immuno-fluorescence

A microscopic technique using fluorescent markers bound to antibodies to identify and visualize specific target antigens within cells.

Freeze-Fracture Electron Microscopy

A technique involving flash-freezing cells, fracturing them along membrane hydrophobic cores, and casting a metal replica for high-resolution 3D examination.

Cryogenic Electron Microscopy (Cryo-EM)

A method where protein solutions are flash-frozen in vitreous ice and analyzed with electron beams to reconstruct 3D models of biological macromolecules at near-atomic resolution.

Nucleoid

The non-membrane-bound, pale region within the cytoplasm of a prokaryotic cell that contains its naked, circular DNA molecule.

Peptidoglycan

A rigid layer composed of sugars and amino acids that forms the cell wall surrounding the plasma membrane in prokaryotes.

Histones

Globular proteins found in eukaryotic nuclei around which linear DNA molecules wrap to form chromatin structures.

Syncytium

A continuous multinucleated cellular structure formed by the fusion of several individual cells, such as a skeletal muscle fiber.

Coenocyte

A multinucleate cell structure resulting from repeated nuclear divisions without subsequent cytoplasmic division, as seen in aseptate fungal hyphae.

Rough Endoplasmic Reticulum (rER)

A eukaryotic membrane network of flattened sacs (cisternae) studded with $80\text{S}$ ribosomes, specialized in synthesizing proteins for secretion or membranes.

Endosymbiotic Theory

The evolutionary theory asserting that eukaryotic organelles like mitochondria and chloroplasts originated as free-living prokaryotes that were ingested by host cells via endocytosis.

Capsid

The protective protein shell composed of repeating protein subunits that encapsulates viral genetic material.

Retrovirus

An RNA virus that utilizes the enzyme reverse transcriptase to synthesize a double-stranded DNA copy of its viral RNA genome inside host cells.

Lytic Cycle

A viral replication pathway in which a virus replicates rapidly inside a host cell and subsequently lyses the cell membrane to release new viral particles.

Lysogenic Cycle

A viral pathway where viral DNA integrates into the host cell chromosome as a prophage and replicates passively without destroying the host.

Prophage

The viral genome that has integrated into the circular DNA of a host bacterial chromosome during the lysogenic cycle.

Progressive Hypothesis

The proposal that viruses evolved stepwise from cellular genetic fragments, such as retrotransposons, that acquired the capacity to exit and enter cells.

Regressive Hypothesis

The proposal that viruses originated from parasitic cellular organisms that underwent evolutionary simplification and lost metabolic and cellular components over time.

Haemagglutinin

An antigenic protein located on the surface of the influenza virus that binds to host cell surface receptors to facilitate entry.

Neuraminidase

An antigenic surface enzyme of the influenza virus that assists newly generated virions in exiting the host cell.

Abiogenesis

The natural evolutionary process by which living organisms first arose from non-living organic compounds on early Earth.