Nester's Microbiology Chapter 03: Prokaryotic and Eukaryotic Cells

Comprehensive practice flashcards covering cell structure, transport, microscopy, and staining techniques from Chapter 3.

Who developed the staining method that identifies two major groups of bacteria based on cell wall structure?

Hans Christian Joachim Gram (1853 to 1938)

What is the basis for the modern Gram stain used in microbiology?

It identifies two major groups of bacteria (Gram-positive and Gram-negative) according to cell wall structure and chemistry.

Which organisms are classified as having prokaryotic cells?

The cells of all bacteria and archaea.

Which organisms are classified as having eukaryotic cells?

All animals, plants, protozoa, fungi, and algae.

What is the benefit of the high surface-area-to-volume ratio in prokaryotic cells?

It makes it easier for the cells to take in nutrients and excrete waste products.

What structures constitute the cell envelope of a prokaryotic cell?

The cytoplasmic membrane, the cell wall, and the capsule (if present).

Describe the structure of the cytoplasmic membrane according to the fluid mosaic model.

A phospholipid bilayer embedded with proteins that drift about in the lipid bilayer.

How do the phospholipid compositions of Bacteria and Archaea differ?

The lipid tails of Archaea are not fatty acids and are connected differently to glycerol.

What process involves the movement of a substance from high to low concentration until equilibrium is reached?

Simple Diffusion

Define osmosis.

The diffusion of water across a selectively permeable membrane from a hypotonic solution (low solute concentration) to a hypertonic solution (high solute concentration).

What is proton motive force, and where is it generated in prokaryotes?

An electrochemical gradient created by the Electron Transport Chain (ETC) embedded in the cytoplasmic membrane.

What is the function of efflux pumps in bacterial cells?

They move waste products and toxic substances, such as antimicrobial medications, out of the cell.

What is group translocation?

A transport process common in bacteria where a compound is chemically altered (often via phosphorylation) during passage through the cytoplasmic membrane.

What are the two primary subunits of peptidoglycan?

$N-acetylmuramic\ acid$ (NAM) and $N-acetylglucosamine$ (NAG).

Differentiate the peptidoglycan linkage in Gram-negative versus Gram-positive cells.

Gram-negative cells have a direct link between glycan chains, while Gram-positive cells use a peptide interbridge.

Identify two unique features of the Gram-positive cell wall.

A relatively thick peptidoglycan layer and teichoic acids.

What is the outer membrane of Gram-negative bacteria composed of?

Lipopolysaccharide (LPS), also known as endotoxin.

What are the three components of Lipopolysaccharide (LPS)?

Lipid A (recognized by the immune system), core polysaccharide, and O antigen (used to identify species or strains).

How does penicillin affect bacteria?

It interferes with peptidoglycan synthesis by preventing the cross-linking of adjacent glycan chains.

How does lysozyme affect the bacterial cell wall?

It breaks the bonds linking the glycan chains (NAM and NAG), destroying the structural integrity of peptidoglycan.

Which genus of bacteria naturally lacks a cell wall and has sterols in its membrane?

Mycoplasma

Define chemotaxis.

The movement of bacteria toward a nutrient (attractant) or away from a toxin (repellent) via a series of runs and tumbles.

What is the function of sex pili?

They are used to join one bacterium to another for DNA transfer.

What are the Svedberg units ($S$) for prokaryotic and eukaryotic ribosomes?

Prokaryotic ribosomes are $70S$; eukaryotic ribosomes are $80S$.

What are endospores, and which genera typically produce them?

Unique, dormant, and highly resistant cells produced by members of Bacillus and Clostridium.

What substance is found in the core of an endospore and plays a protective role?

Calcium dipicolinate

According to the endosymbiotic theory, what were the ancestors of mitochondria and chloroplasts?

Bacteria that resided within other cells.

What are the three key concepts of light microscopy?

Magnification, Resolution, and Contrast.

What is the purpose of immersion oil in microscopy?

It displaces air between the lens and specimen to prevent refraction of light when using the $100\times$ objective.

Which microscope uses a laser beam to illuminate successive planes of a specimen to construct a 3D image?

Confocal microscope

Name the two major types of electron microscopes.

Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM).

Why is the acid-fast stain used for Mycobacterium species?

Because their cell walls contain high concentrations of mycolic acids, which do not readily take up traditional dyes.