Microscopy and Staining

A set of flashcards covering key concepts from the lecture on microscopy and staining techniques.

Refraction

The bending of light as it passes from one medium to another, such as from air into glass.

Focal Point

The point where light rays converge after passing through a lens.

Focal Length

The distance between the center of a lens and its focal point.

Resolution

The ability to distinguish between two separate objects.

Numerical Aperture (NA)

A measure of the light-gathering ability of a lens; it affects the resolution.

Immersion Oil

A type of oil used to increase the numerical aperture of a lens system by allowing closer proximity to the specimen.

Heat Fixation

A method to adhere bacterial cells to a slide by passing it through a flame.

Chemical Fixation

A process that uses chemicals to protect the internal structure of cells.

Chromophore

A part of a dye that gives it color and helps it bind to cellular components.

Positive Staining

A staining technique where the dye binds to the cells to increase contrast with the background.

Negative Staining

A method where the cells remain unstained, and the background is dark, allowing visualization of the cells.

Differential Staining

Techniques that allow different types of cells or cellular components to be distinguished based on their staining properties.

Gram-positive

Bacteria that retain crystal violet stain, appearing purple after the Gram stain procedure.

Gram-negative

Bacteria that lose the crystal violet stain and are counterstained with safranin, appearing red after the Gram stain procedure.

Acid-fast Staining

A differential staining technique used to identify bacteria with high lipid content in their cell walls, such as Mycobacterium.

Darkfield Microscopy

A microscopy technique that illuminates the specimen from the sides, making it appear bright against a dark background.

Phase-Contrast Microscopy

A method that amplifies differences in light refraction to improve contrast and visualization of transparent specimens.

Fluorescence Microscopy

A technique that uses fluorescent dyes to illuminate specimens, emitting light of longer wavelengths when excited by shorter wavelengths.

Cationic Dyes

Basic dyes with positively charged groups that bind to negatively charged materials in cells.

Anionic Dyes

Acidic dyes with negatively charged groups that bind to positively charged materials in cells.

Fat-Soluble Stains

Stains that dissolve in lipids and are used to visualize lipid inclusions in cells.

Capsule Staining

A staining method used to visualize the presence of capsules around bacteria.