Cell Structure Pt 1: Membrane Transport, Morphology, and Microscopy

Comprehensive vocabulary flashcards covering bacterial cell wall envelopes, membrane transport, biofilm formation, microscopy concepts, and staining techniques from the CSP305 Lecture.

Cell Envelope

The outer structure of a cell that includes the membrane(s) and cell wall, helping the cell maintain its specific shape.

Gram-positive cell wall

A bacterial cell wall structure consisting of a cytoplasmic membrane and a thick peptidoglycan layer that stains purple during Gram staining.

Gram-negative cell wall

A bacterial cell wall structure consisting of a cytoplasmic membrane, a thin peptidoglycan layer in the periplasm, and an outer membrane that stains pink during Gram staining.

Outer membrane

A structure found only in gram-negative bacteria consisting of a phospholipid bilayer, lipopolysaccharides, and porin proteins; functions in mechanical strength, surface recognition, and virulence.

Lipopolysaccharide (LPS)

A component of the outer membrane in gram-negative bacteria that acts as an endotoxin and pyrogen, causing fever.

Peptidoglycan

A cell wall component composed of alternating sugars/carbohydrates crosslinked by peptide bonds that maintains cell shape, resists turgor pressure, and prevents lysis.

Lysozyme

An enzyme that breaks down peptidoglycan.

Plasma membrane

A selectively permeable boundary containing peripheral and integral membrane proteins that surrounds the cytoplasm and controls the movement of waste and nutrients into and out of the cell.

Passive transport

Transport across the cell membrane that moves substances with the concentration gradient and does not require ATP for energy.

Active transport

Transport across the cell membrane that moves substances against the concentration gradient and requires ATP for energy.

Isotonic

An environmental condition characterized by having the same concentration of solute on the inside and outside of the cell membrane.

Hypertonic

An environmental condition characterized by a higher concentration of solute outside of the cell than inside of the cell membrane.

Hypotonic

An environmental condition where the concentration of solute is lower outside the cell than inside the cell membrane, which results in the lysis of cells without cell walls.

Glycocalyx

An outer coating comprising capsules and slime layers that increases bacterial virulence and helps pathogens evade the host immune system.

Capsule

A firmly arranged carbohydrate coating belonging to the glycocalyx.

Slime layer

A loosely arranged carbohydrate coating belonging to the glycocalyx.

Biofilms

Bacterial attachments to surfaces (e.g., plaque) that begin with one type of bacterium adhering to a surface, followed by attachment of other cells to form colonies that optimize nutrient utilization.

Resolution

Also known as resolving power; the ability to distinguish two points, where a lower "d" number denotes higher/better resolution, improved by increasing numerical aperture (NA) or decreasing wavelength.

Oil immersion

A microscopy technique that increases the numerical aperture (NA) value by preventing light from scattering, allowing more light to enter the objective lens to produce an improved image.

Koehler illumination

A microscopy illumination method that ensures even illumination to produce a sharper image.

Contrast

The visual difference between the subject and the background in microscopy.

Transmission electron microscope

A specialized electron microscope with a resolution capability of $0.2\text{ nm}$.

Basic dye

A positively charged stain (e.g., methylene blue, safranin, crystal violet) that binds to negatively charged cell surfaces.

Acidic dye

A negatively charged stain (e.g., eosin, nigrosine) that is repelled by negatively charged cells.

Differential stain

A staining procedure using multiple stains, reagents, and steps to distinguish between cell types or structures.

Endospore stain

A differential stain that colors vegetative cells pink and spores green.

Negative stain

An acidic stain repelled by negatively charged capsules, used to distinguish bacterial capsules.

Acid-fast stain

A differential stain that distinguishes bacteria containing waxy mycolic acid, turning acid-fast bacteria pink and non-acid-fast bacteria blue.