Microbiology: Cell Structure and Evolutionary Foundations

Practice flashcards covering Chapter 3 lecture content on spontaneous generation, cell theory, prokaryotic structures, and eukaryotic organelles.

What is the theory of spontaneous generation as articulated by Aristotle?

The notion that life can arise from nonliving matter if the material contains pneuma ("spirit" or "breath").

What are the two fundamental tenets of modern cell theory?

1. All cells only come from other cells (the principle of biogenesis).

2. Cells are the fundamental units of organisms.

Which scientist first used the term "cells" in 1665 when observing cork under a microscope?

Robert Hooke

Which two scientists contributed key evidence that cells originate from cell division, leading to the phrase "omnis cellula a cellula"?

Robert Remak published evidence in 1852 that cells derive from cell division, and Rudolf Virchow popularized the concept in an 1855 essay using the phrase "omnis cellula a cellula."

What does the modern endosymbiotic theory state, and who resurrected it in 1967 with supportive data?

It states that mitochondria and chloroplasts arose as a result of prokaryotic cells establishing a symbiotic relationship within a eukaryotic host; it was resurrected by Lynn Margulis.

How did the miasma theory explain the cause of disease compared to the germ theory of disease?

Miasma theory claimed disease originated from foul particles emanating from decomposing matter, whereas germ theory states that diseases result from microbial infection.

What are the cell shapes for Coccus, Bacillus, Vibrio, Spirillum, and Spirochete?

Coccus: round; Bacillus: rod; Vibrio: curved rod; Spirillum: spiral; Spirochete: long, loose, helical spiral.

How are Diplococcus, Tetrad, Streptococcus, and Staphylococcus arrangements described?

Diplococcus: pair of two cocci; Tetrad: grouping of four cells arranged in a square; Streptococcus: chain of cocci; Staphylococcus: cluster of cocci.

How do non-walled cells and walled cells differ in their response to a hypertonic environment?

Cells without cell walls undergo crenation (shriveling), whereas cells with cell walls undergo plasmolysis (the plasma membrane contracts and detaches from the cell wall).

What is sporulation in bacteria, and what chemical components accumulate in the endospore cortex?

Sporulation is the process where a vegetative cell transforms into a dormant endospore; calcium and dipicolinic acid accumulate in the cortex to protect the DNA core.

How do archaeal membrane lipids differ structurally from bacterial and eukaryotic membrane lipids?

Archaeal lipids contain ether linkages instead of ester linkages, have branched chains instead of straight chains, and can form lipid monolayers instead of bilayers.

What is the basic chemical composition of bacterial peptidoglycan?

Long chains of alternating molecules of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by peptide bridges.

How do the cell walls of Gram-positive and Gram-negative bacteria differ?

Gram-positive cell walls have a thick layer of peptidoglycan embedded with teichoic acids; Gram-negative cell walls have a thin peptidoglycan layer, a periplasmic space, and an outer membrane containing lipopolysaccharide (LPS).

What is the structural difference between a capsule and a slime layer?

A capsule is an organized, tightly attached layer outside the cell wall; a slime layer is a less organized, loosely attached layer that can be easily washed off.

What are the definitions of Monotrichous, Amphitrichous, Lophotrichous, and Peritrichous flagella?

Monotrichous: a single polar flagellum; Amphitrichous: flagella or tufts at both ends; Lophotrichous: a tuft of flagella at one end; Peritrichous: flagella covering the entire cell surface.

Which organelles comprise the eukaryotic endomembrane system?

Endoplasmic reticulum (rough and smooth), Golgi apparatus, lysosomes, and vesicles.

What is the basic chemical composition of bacterial peptidoglycan?

Long chains of alternating molecules of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by peptide bridges.

How do the cell walls of Gram-positive and Gram-negative bacteria differ?

Gram-positive cell walls have a thick layer of peptidoglycan embedded with teichoic acids; Gram-negative cell walls have a thin peptidoglycan layer, a periplasmic space, and an outer membrane containing lipopolysaccharide (LPS).

Which organelles comprise the eukaryotic endomembrane system?

Endoplasmic reticulum (rough and smooth), Golgi apparatus, lysosomes, and vesicles.

Nucleoid region and DNA packaging in prokaryotes

The condensed cytoplasmic region containing the circular bacterial chromosome, organized using nucleoid-associated proteins (NAPs) in bacteria or histone-like proteins in archaea.

Plasmids

Small, circular, double-stranded extrachromosomal DNA molecules that often carry advantageous traits such as antibiotic resistance.

Comparison of non-organellar eukaryotic ribosomes and organellar ribosomes

Non-organellar eukaryotic ribosomes in the cytoplasm and rough ER are $80\text{S}$ (composed of $40\text{S}$ and $60\text{S}$ subunits), whereas organellar ribosomes inside mitochondria and chloroplasts are $70\text{S}$.

Rough Endoplasmic Reticulum vs. Smooth Endoplasmic Reticulum

• Rough ER (RER): studded with ribosomes on the cytoplasmic side; synthesizes membrane-bound or secreted proteins • Smooth ER (SER): lacks ribosomes; synthesizes lipids, metabolizes carbohydrates, and detoxifies toxic compounds

Golgi apparatus structure and function

Composed of stacked membranous disks called dictyosomes with cis (receiving) and trans (shipping) faces; modifies proteins and lipids by adding carbohydrates to form glycoproteins or glycolipids for transport or exocytosis.

Lysosomes

Membrane-bound organelles containing digestive enzymes used to break down food, damaged organelles, cellular debris, or pathogens; discovered by Christian de Duve.

Peroxisomes and their specialized forms

Organelles that produce hydrogen peroxide to break down molecules and contain catalase to degrade it; specialized forms include glyoxysomes (in yeast/plants for sugar production) and glycosomes (in trypanosomes).

Mitochondrial structural features

Double-membrane organelle containing inner membrane folds (cristae), a fluid matrix, its own circular bacterial-like DNA, and $70\text{S}$ ribosomes.

Chloroplast structural organization

Organelle bounded by outer and inner membranes, containing a gel-like stroma and a thylakoid membrane system arranged in stacks called grana where chlorophyll resides.

The three main components of the eukaryotic cytoskeleton

1. Microfilaments: intertwined actin strands ($6\,nm$ diameter) involved in amoeboid movement, cytoplasmic streaming, and cleavage furrows

2. Intermediate filaments: diverse strands ($10\,nm$ diameter) maintaining nuclear lamina and tissue integrity (e.g., keratin, desmin)

3. Microtubules: hollow tubulin dimer tubes ($23\,nm$ diameter) involved in organelle movement, mitotic spindle formation, cilia, and flagella

Mitosis vs. Meiosis in eukaryotic cells

• Mitosis: single nuclear division after G1, S, and G2 interphase phases, producing two identical diploid ($2n$) daughter cells • Meiosis: two nuclear divisions producing four genetically distinct haploid ($n$) gametes