Ch 3: Microscopy and Cell Structure (Flashcards)

Vocabulary flashcards covering microscopy techniques, staining methods, prokaryotic morphology, cell structures, and basic eukaryotic organelles.

Light microscope

A microscope that uses visible light to observe specimens, typically up to ~1000x magnification.

Electron microscope

A microscope that uses electrons and electromagnetic lenses to achieve magnifications well over 100,000x with high resolution.

Atomic force microscope

AFM; a microscope introduced in 1981 that can view individual atoms by scanning a surface with a nanoscale probe.

Magnification

The enlargement of an image; for compound microscopes it is ocular × objective magnification.

Resolution

The ability to distinguish two closely spaced objects as separate; depends on lenses, wavelength, and specimen prep.

Bright-field microscope

The most common light microscope where the specimen is viewed against a bright background.

Condenser lens

Lenses that focus light on the specimen; they do not affect magnification in bright-field microscopy.

Ocular lens

Eyepiece of a compound microscope that magnifies the image produced by the objective.

Objective lens

Primary lenses (e.g., 4x, 10x, 40x, 100x) on a microscope that form the initial image.

Compound microscope

A microscope with two sets of lenses (ocular and objective) for magnification.

Immersion oil

Oil with a refractive index close to glass used with 100x objectives to increase resolution.

Refractive index

A measure of how much a medium bends light; higher index reduces refraction at interfaces.

Phase-contrast microscope

A light microscope that enhances contrast by exploiting differences in refractive indices.

Interference microscope

A microscope that uses interference of light waves to improve contrast or detail.

Dark-field microscope

Illuminates specimens with oblique light so only scattered light enters the objective for high-contrast imaging.

Fluorescence microscope

Uses UV light to excite fluorescent molecules; specimens emit visible light on a dark background.

Confocal scanning laser microscope

Constructs 3D images by scanning specimens with a laser and compiling optical sections.

Transmission electron microscope (TEM)

Electron microscope that passes electrons through a thin specimen to reveal internal details.

Scanning electron microscope (SEM)

Electron microscope that scans the surface of a specimen to produce detailed 3D-like images.

Dyes

Colored molecules that bind to cellular structures to increase contrast; can be basic or acidic.

Basic dye

Positively charged dye that binds to negatively charged cell components.

Acidic dye

Negatively charged dye that stains the background and is repelled by cell components.

Simple stain

A staining procedure using one basic dye to stain all cells the same color.

Heat fixation

Process of fixing cells to a slide by briefly heating to preserve morphology.

Gram stain

Differential stain that divides bacteria into Gram-positive (purple) and Gram-negative (red/pink).

Crystal violet

Primary stain in Gram staining that colors all cells purple.

Gram’s iodine

Mordant in Gram staining that helps fix the crystal violet to cells.

Decolorizer

Alcohol used in Gram staining to remove dye from Gram-negative cells.

Safranin

Counterstain in Gram staining that colors decolorized Gram-negative cells pink.

Acid-fast stain

Stain for organisms with high lipid content in their cell walls (e.g., Mycobacterium).

Mycobacterium

Genus with waxy, lipid-rich cell walls; includes TB and Hansen’s disease; acid-fast positive.

Capsule stain

Staining method to visualize capsules as halos around cells; capsule is a distinct layer.

Negative stain

Stain in which the background is colored and the capsule remains clear; India ink is a common example.

Endospore stain

Stain that highlights endospores, often using heat to facilitate staining.

Flagella stain

Staining technique to enlarge and visualize bacterial flagella.

Coccus

Spherical prokaryotic cell shape.

Bacillus

Rod-shaped prokaryotic cell shape; not to be confused with the genus Bacillus.

Coccobacillus

Short, oval-shaped rod; intermediate between cocci and bacilli.

Vibrio

Comma-shaped (curved rod) prokaryotic cell.

Spirillum

Spiral-shaped prokaryotic cell.

Spirochete

Tightly coiled, helical-shaped prokaryotic cell.

Pleomorphic

Bacteria that can vary in shape rather than have a single form.

Diplococci

Pairs of cocci formed by bacterial Division in one plane.

Streptococci

Chains of cocci formed by successive divisions.

Sarcina

Cubical packets of cocci formed by division in three perpendicular planes.

Staphylococcus

Bacteria that form irregular, grape-like clusters of cocci.

Myxobacteria

Group of bacteria that form multicellular swarms and fruiting bodies; produce slime layers.

Biofilm

Structured microbial community attached to a surface; alters cellular behavior.

Capsule

Gelatinous layer outside the cell wall that protects against host defenses and aids adhesion.

Slime layer

Irregular, diffuse outer layer that aids adherence and protection.

Flagella

Long protein appendages responsible for bacterial motility.

Pili

Short, thin appendages used for attachment; some for DNA transfer (sex pili).

Fimbria

Small pili used for attachment to surfaces.

Conjugation (sex pili)

DNA transfer between bacteria via contact through sex pili.

Filament

Main hollow thread of a flagellum extending from the cell outward.

Hook

Connects the filament to the basal body in a flagellum.

Basal body

Anchors the flagellum to the cell envelope and powers rotation.

Nucleoid

Region in a prokaryotic cell containing the chromosome; not membrane-bound.

Chromosome

Typically a single circular double-stranded DNA molecule containing the genome.

Plasmid

Small circular DNA molecule that replicates independently and can carry accessory genes.

Ribosome

Complex for protein synthesis; 70S in prokaryotes (50S + 30S subunits).

Storage granule

Polymer storage bodies (e.g., glycogen) that store excess nutrients.

Gas vesicles

Protein-bound compartments that provide buoyancy to aquatic bacteria.

Endospore

Dormant, highly resistant cell type produced by some bacteria; persists for long periods.

Sporulation

Process of endospore formation in response to adverse conditions.

Germination

Resumption of metabolic activity and growth from a dormant endospore.

Pseudopod

Temporary projection of the cytoplasm used for movement or phagocytosis in some cells.

Nucleus

Membrane-bound organelle in eukaryotes containing dsDNA wrapped around histones.

Mitochondria

Organelle for ATP production; double membrane with cristae and matrix.

Cristae

Infoldings of the inner mitochondrial membrane that increase surface area.

Matrix

Fluid inside the mitochondrion containing enzymes, DNA, and ribosomes.

Chloroplast

Site of photosynthesis in plants and algae; contains chlorophyll and has two membranes.

Endoplasmic reticulum (ER)

Network of membranes; rough ER has ribosomes for protein synthesis; smooth ER synthesizes lipids.

Rough endoplasmic reticulum

ER studded with ribosomes; site of protein synthesis for secretion or membranes.

Smooth endoplasmic reticulum

ER lacking ribosomes; lipid synthesis and calcium storage.

Golgi apparatus

Stacked membranes that modify, sort, and package macromolecules for secretion or delivery.

Lysosome

Organelle containing degradative enzymes for digestion within the cell.

Peroxisome

Organelle involved in lipid metabolism and breakdown of reactive oxygen species.

Ribosome (eukaryotic)

80S ribosome (60S large subunit + 40S small subunit) in eukaryotes.

9+2 arrangement

Structural arrangement of microtubules in eukaryotic flagella and cilia.

Cilia

Short, numerous projections used for movement or to move surrounding fluids.