MCAT Biological and Biochemical Foundations of Living Systems Flashcards: 2b Cell Theory Prokaryotic Structure

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This deck focuses on 2b Cell Theory Prokaryotic Structure, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Biological and Biochemical Foundations of Living Systems.

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Flashcard 1: Identify the correct classification: a cell has a nucleoid, plasmids, and $70S$ ribosomes.

Answer: Prokaryotic cell. These features indicate a prokaryote, lacking eukaryotic nuclear membranes and larger ribosomes.

Flashcard 2: Which cell structures are present in both prokaryotes and eukaryotes?

Answer: Plasma membrane, cytosol, DNA, and ribosomes. These universal components enable basic cellular functions like enclosure, metabolism, heredity, and protein synthesis across all cell types.

Flashcard 3: What is the nucleoid in a prokaryotic cell?

Answer: Non-membrane-bound region containing the bacterial chromosome. The nucleoid organizes the prokaryotic genome without a nuclear envelope, allowing direct cytoplasmic access.

Flashcard 4: What modification to cell theory accounts for heredity in modern cell theory?

Answer: Cells contain hereditary information (DNA) passed to daughter cells. This addition incorporates the role of DNA in inheritance, reflecting advances in genetics since the original cell theory.

Flashcard 5: What are fimbriae, and what is their primary role in bacteria?

Answer: Short surface appendages used mainly for attachment. Fimbriae promote adherence to host tissues or surfaces, crucial for colonization and biofilm formation.

Flashcard 6: What is the bacterial cell wall primarily made of in most bacteria?

Answer: Peptidoglycan (murein). Peptidoglycan provides rigidity and shape, unique to bacterial cell walls and absent in eukaryotes.

Flashcard 7: What is a sex pilus, and what process does it enable?

Answer: Conjugation pilus; transfers DNA between bacteria. The sex pilus forms a bridge for horizontal gene transfer during conjugation, enabling genetic diversity.

Flashcard 8: Which step of cell theory is violated by the claim that cells arise from nonliving matter?

Answer: The tenet that cells arise only from preexisting cells. This claim supports spontaneous generation, contradicting the biogenesis principle of cell theory.

Flashcard 9: What modification to cell theory accounts for shared chemistry in modern cell theory?

Answer: All cells have fundamentally similar chemical composition. This reflects the universal biochemical similarities among cells, supporting evolutionary relatedness.

Flashcard 10: What are the subunits of a prokaryotic $70S$ ribosome?

Answer: $50S$ large subunit and $30S$ small subunit. The $70S$ ribosome assembles from these subunits to facilitate protein synthesis in prokaryotes.

Flashcard 11: What is binary fission in prokaryotes?

Answer: Asexual division producing two genetically identical daughter cells. Binary fission ensures rapid reproduction without genetic variation, typical of prokaryotic growth.

Flashcard 12: What is the primary function of bacterial flagella?

Answer: Motility via rotation driven by a proton motive force. Flagella enable chemotaxis and movement, powered by ion gradients across the membrane.

Flashcard 13: Which statement best describes spontaneous generation relative to cell theory?

Answer: It is rejected; new cells arise only from preexisting cells. Cell theory's third tenet directly opposes spontaneous generation by asserting biogenesis.

Flashcard 14: What is the size of prokaryotic ribosomes, and what is the eukaryotic cytosolic size?

Answer: Prokaryotic $70S$; eukaryotic cytosolic $80S$. Ribosome sizes differ due to subunit compositions, with prokaryotic ones being smaller and targeted by certain antibiotics.

Flashcard 15: Identify the Gram stain result: a bacterium has an outer membrane and LPS; what color stains?

Answer: Pink (Gram-negative). Gram-negative bacteria have these structures, leading to decolorization and pink staining with safranin.

Flashcard 16: What modification to cell theory accounts for metabolism in modern cell theory?

Answer: Energy flow (metabolism) occurs within cells. This emphasizes that cells are sites of biochemical activity, aligning with modern understanding of cellular energetics.

Flashcard 17: What is the periplasmic space in Gram-negative bacteria?

Answer: Space between inner and outer membranes containing thin peptidoglycan. The periplasm houses enzymes and the cell wall, providing a compartment for processes like nutrient breakdown.

Flashcard 18: Which bacterial group has a thin peptidoglycan layer plus an outer membrane and stains pink?

Answer: Gram-negative bacteria. The outer membrane prevents crystal violet retention, allowing counterstain with safranin for pink appearance.

Flashcard 19: Which bacterial group has a thick peptidoglycan layer and stains purple on Gram stain?

Answer: Gram-positive bacteria. The thick layer retains crystal violet dye during Gram staining, indicating structural differences from Gram-negative bacteria.

Flashcard 20: What is a plasmid in bacteria?

Answer: Small circular extrachromosomal DNA that replicates independently. Plasmids provide bacteria with accessory genes, often for advantages like antibiotic resistance, separate from the main chromosome.

Flashcard 21: What are the three classical tenets of cell theory?

Answer: All organisms are cellular; cells are basic unit; cells arise from cells. These tenets, established by Schleiden, Schwann, and Virchow, form the foundation of understanding cellular organization and reproduction in biology.

Flashcard 22: What is the defining structural feature of a prokaryotic cell compared with a eukaryotic cell?

Answer: No membrane-bound nucleus or membrane-bound organelles. Prokaryotes lack compartmentalization provided by membranes, distinguishing them from eukaryotes with true nuclei and organelles.

Flashcard 23: Which structure is directly targeted by lysozyme: peptidoglycan, LPS, or cholesterol?

Answer: Peptidoglycan. Lysozyme hydrolyzes eta-1,4 linkages in peptidoglycan, weakening bacterial cell walls.

Flashcard 24: What is the capsule (glycocalyx) in some bacteria, and what is its main function?

Answer: External polysaccharide layer; protects and aids adhesion/biofilms. The capsule enhances virulence by evading host immunity and facilitating surface attachment.

Flashcard 25: What molecule in Gram-negative bacteria is a major endotoxin and strong immune activator?

Answer: Lipopolysaccharide (LPS), especially lipid A. LPS in the outer membrane triggers intense immune responses, contributing to pathogenicity in Gram-negative infections.