Cell Biology Methods - Experimental Models, Microscopy, and Cell Separation

Vocabulary flashcards covering biological experimental model organisms, primary and 3D cell culture systems, light and electron microscopy types and limits, cell fractionation techniques, and flow cytometry/cell sorting.

Escherichia coli (E. coli)

A prokaryotic bacterium widely used for molecular genetics (DNA replication, gene expression, protein synthesis), metabolic pathway determination, and biotechnology, characterized by simplicity, a small genome, and rapid propagation (division every $20\,\text{minutes}$).

Saccharomyces cerevisiae

The simplest eukaryotic model organism (yeast), containing a nucleus, linear chromosomes, cytoskeleton, and organelles, which is easily cultured and rapidly propagates by dividing every $2\,\text{hours}$.

Caenorhabditis elegans (C. elegans)

A microscopic nematode used in developmental biology that contains exactly 959 somatic cells, where the precise embryonic origin and lineage of every cell is completely mapped.

Drosophila melanogaster

A multicellular insect model organism (fruit fly) widely utilized to investigate developmental biology and gene interactions, known for its ease of laboratory maintenance and rapid reproduction cycle of every 2 weeks.

Arabidopsis thaliana

A small weed used as a primary plant model organism in developmental biology experiments, such as flower development, due to its small genome and ease of growth in the laboratory.

Xenopus laevis

An amphibian model organism used to investigate embryonic cell division, differentiation, and early vertebrate development because it produces large ($1\,\text{mm}$), numerous eggs that develop externally.

Danio rerio (Zebrafish)

A small, transparent vertebrate model organism with externally developing embryos, utilized to study developmental mutations and bridge the gap between simple invertebrates and humans.

Piebaldism

A genetic condition characterized by pigmentation defects caused by mutations in a gene required for the normal embryonic migration of melanocytes, presenting homologous manifestations in both humans and mice.

Primary Cell Culture

The initial culture established by enzymatically or mechanically dispersing cells directly from an animal or human tissue and seeding them onto a culture dish in liquid nutrient medium.

Secondary Cell Culture

A cell culture prepared by dissociating cells from a confluent primary culture dish and replating them at a lower density in fresh medium to permit continued proliferation.

Electroporation

A physical transfection method in which target cells placed in solution between two electrodes receive a brief high-voltage electric shock, creating transient pores in the plasma membrane that allow external molecules to enter.

Organoids

Three-dimensional, self-assembled clusters of cells or mini-organs derived from stem cells or tissue biopsies that mimic in vivo organ structure and function better than traditional 2D cell cultures.

Organ-on-a-chip

A microfluidic cell culture device containing living cells under continuous fluid flow to mimic organ physiology and vascular connections on a substrate roughly the size of a glass microscope slide.

Resolution Limit of Light Microscopy

The minimum distance between two distinct points at which they can still be resolved as separate objects using visible light, which is approximately $0.2\,\mu\text{m}$.

Resolution Limit of Electron Microscopy

The resolving capacity achieved by utilizing high-velocity electron beams with short wavelengths, typically ranging from $0.1\,\text{nm}\text{ to }0.2\,\text{nm}$.

Bright-Field Microscope

The simplest light microscope where light transmits directly through the specimen; contrast relies on differential light absorption, typically requiring cells to be fixed and stained with dyes.

Dark-Field Microscope

A light microscopy system where a specialized condenser directs light obliquely toward the specimen so only scattered light enters the objective, rendering unstained, live microorganisms bright against a dark background.

Phase-Contrast Microscope

A microscope that converts slight phase shifts in light waves passing through cellular structures into visible differences in brightness and contrast, allowing unstained living cells to be studied in real time.

Differential Interference Contrast (DIC) Microscope

An optical microscope that uses polarized light split into two slightly separated beams to generate high contrast and pseudo-3D relief images, particularly highlighting the edges of living, unstained cells.

Fluorescence Microscope

A light microscope that illuminates a sample with excitation light of a specific short wavelength and uses emission filters to detect longer wavelengths emitted by fluorophores bound to specific cellular targets.

Confocal Microscope

An optical microscope that uses a focused laser beam and pinhole aperture to eliminate out-of-focus light from above and below the focal plane, generating thin optical sections that can be reconstructed into 3D images.

Fluorescence In Situ Hybridization (FISH)

A molecular cytogenetic technique using fluorophore-labeled complementary nucleic acid probes to detect and localize specific DNA or RNA sequences inside preserved cells or tissue sections.

Transmission Electron Microscope (TEM)

An electron microscope that directs an electron beam through an ultra-thin specimen; structures that scatter electrons appear dark on a fluorescent screen or detector, revealing internal subcellular ultrastructure.

Scanning Electron Microscope (SEM)

An electron microscope that scans a focused electron beam across a heavy-metal-coated specimen surface to detect secondary electrons, generating high-resolution, three-dimensional topological images.

Differential Centrifugation

A cell fractionation procedure in which a tissue homogenate is centrifuged at sequentially increasing speeds, sedimenting larger or denser organelles first (nuclei at low speed, mitochondria/lysosomes at medium, microsomes at high, ribosomes at very high).

Density Gradient Centrifugation

A high-purity fractionation technique where cell homogenates or organelles sediment through an increasing density gradient of sucrose or cesium chloride until reaching their isopycnic or sedimentation equilibrium.

Fluorescence-Activated Cell Sorting (FACS)

A flow cytometry-based method in which single cells labeled with fluorescent antibodies are analyzed by a laser, assigned an electrostatic charge according to fluorescence, and deflected by high-voltage plates into designated collection tubes.