Prokaryote

. What are the four statements of cell theory emphasized in this lecture?

Answer: 1) Cells are the fundamental units of life. 2) All living organisms are composed of cells. 3) All cells come from preexisting cells. 4) Cells evolved from a common ancestral cell(s).

Extra context: Exam tip: Be able to state all four without notes. The lecture's fourth point is an evolutionary extension of classical cell theory. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

2. What is the smallest/fundamental unit of life?

Answer: The cell.

Extra context: Outside context: Modern cell theory treats the cell as the basic structural and functional unit of living organisms. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

3. Why can't cells simply keep getting larger? What is the key limiting principle?

Answer: As a cell gets larger, its surface-area-to-volume ratio decreases. The membrane then has less surface area relative to the amount of cytoplasm it must support, making exchange of nutrients, gases, wastes, and other materials less efficient.

Extra context: Outside context: For a sphere, surface area scales with r² while volume scales with r³, so volume increases faster than surface area. This is why large cells face transport/diffusion limits. Source: OpenStax Biology 2e, §4.2. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

4. As cell radius increases, what happens to surface area, volume, and surface-area-to-volume ratio?

Answer: Surface area increases, but volume increases faster; therefore the surface-area-to-volume ratio decreases.

Extra context: Outside context: This is a geometry consequence: SA ∝ r², while V ∝ r³. Source: OpenStax Biology 2e, §4.2. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

5. What is the high-size limit of a cell, in functional terms?

Answer: The cell becomes too large to exchange materials efficiently enough across its plasma membrane to support its volume.

Extra context: Outside context: A large cell can compensate somewhat by changing shape, increasing membrane surface area, or compartmentalizing functions, but the basic SA:V constraint remains. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

6. What is the low-size limit of a cell? Why can't cells become infinitely small?

Answer: A cell must be large enough to physically contain the minimum machinery needed for life—genetic material, ribosomes/protein-synthesis machinery, membrane systems, metabolic enzymes, and other essential components.

Extra context: Outside context: The lecture does not give a numerical minimum-size mechanism; this is added context for the stated 'low size limit' objective. Very small cells exist, but they still require enough volume for essential molecular machinery. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

7. What are the approximate size ranges given in the lecture for prokaryotic vs. eukaryotic cells?

Answer: Lecture: prokaryotic cells ≈ 1–10 µm; eukaryotic cells ≈ 5–100 µm.

Extra context: Outside context: OpenStax gives somewhat different broad ranges depending on how cells are defined, so for an exam tied to this lecture, use the lecture's stated ranges. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

8. How do scientists study cells? Name the microscopy approaches shown in this lecture.

Answer: Bright-field microscopy; phase-contrast microscopy; differential interference contrast (DIC) microscopy; stained bright-field microscopy; fluorescence microscopy; confocal microscopy.

Extra context: Lecture page 4 pairs each method with a different way of increasing contrast, selectively labeling structures, or improving optical sectioning. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

9. What is bright-field microscopy best described as in this lecture?

Answer: A method in which light passes directly through the specimen; unstained samples can have low contrast and fine details may be difficult to distinguish.

Extra context: Outside context: Bright-field commonly benefits from staining when cells/structures are otherwise difficult to distinguish. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

10. What does phase-contrast microscopy do that helps with living cells?

Answer: It converts differences in light phase caused by cell structures into differences in brightness/contrast, making otherwise transparent structures easier to see.

Extra context: Outside context: It is especially useful for observing living, unstained cells. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

11. What is the key idea behind differential interference contrast (DIC) microscopy?

Answer: It uses polarized light/interference to create strong contrast from differences in optical path length, producing an image with shadow-like relief.

Extra context: Outside context: The '3D-like' appearance is an optical effect; it does not mean the image is literally a 3D reconstruction. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

12. What is fluorescence microscopy?

Answer: A technique in which fluorescent molecules/labels emit light that allows specific structures or molecules to be visualized.

Extra context: Outside context: Fluorescent labeling can make a particular protein, organelle, or cellular structure stand out from the background. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

13. What is a major advantage of confocal microscopy?

Answer: It uses fluorescence plus optical sectioning to reduce out-of-focus light, allowing clearer images of structures at different depths and enabling 3D reconstructions from image stacks.

Extra context: Outside context: Think 'confocal = optical slices' rather than simply 'more magnification.' Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

14. What is the defining structural difference between prokaryotic and eukaryotic cells?

Answer: Prokaryotes lack membrane-enclosed subcellular compartments such as a nucleus; eukaryotic cells contain membrane-enclosed organelles.

Extra context: Outside context: Both groups still have DNA, ribosomes, cytoplasm, and a plasma membrane. Source: OpenStax Biology 2e, §4.2 and §22.2. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

15. Which domains contain prokaryotes?

Answer: Bacteria and Archaea.

Extra context: Outside context: Eukarya is the third domain and contains eukaryotic organisms. Source: OpenStax Biology 2e, §22.2. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

16. Which major groups are eukaryotic?

Answer: Protists, plants, fungi, and animals.

Extra context: Outside context: The lecture groups these together under Eukaryota/Eukarya. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

17. What four components are shared by all cells according to standard prokaryote/eukaryote comparisons?

Answer: Plasma membrane, cytoplasm, DNA, and ribosomes.

Extra context: Outside context: OpenStax emphasizes these four shared features even though their organization differs between prokaryotes and eukaryotes. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

18. What does 'unicellular' mean?

Answer: Composed of a single cell.

Extra context: Outside context: A unicellular organism still performs all functions necessary for life within that one cell. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

19. What are the three major bacterial cell shapes shown in the lecture?

Answer: Coccus (spherical), bacillus (rod-shaped), and spirillum/spirochete (spiral forms).

Extra context: Exam tip: Match the word to the visual shape. 'Coccus' = round; 'bacillus' = rod; 'spiral' terms = curved/spiral. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

20. What is a coccus? What is a bacillus?

Answer: Coccus = spherical/round cell. Bacillus = rod-shaped cell.

Extra context: Outside context: These are shape terms, not necessarily names of species. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

21. What is a spirillum vs. a spirochete?

Answer: Both are spiral-shaped bacterial morphologies. The lecture distinguishes them as two spiral forms; spirochetes are typically more flexible/thin and have a characteristic corkscrew-like form.

Extra context: Outside context: Exact terminology can vary among textbooks; focus on recognizing both as spiral morphologies. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

22. What do 'streptococcus,' 'staphylococcus,' and 'streptobacillus' describe?

Answer: They describe cell arrangements: Streptococcus = cocci in chains; Staphylococcus = cocci in grape-like clusters; Streptobacillus = rods in chains.

Extra context: Outside context: 'Staph' = clusters; 'strep' = chains is a useful recognition rule. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

23. What is the nucleoid?

Answer: The region of a prokaryotic cell where its chromosome is concentrated; it is not surrounded by a membrane.

Extra context: Outside context: Prokaryotic chromosomes are usually circular and double-stranded, though chromosome organization can be more complex than a simple 'loop.' Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

24. How is the prokaryotic chromosome different from DNA inside a eukaryotic nucleus?

Answer: In prokaryotes, the chromosome is located in the nucleoid, not inside a membrane-bound nucleus. In eukaryotes, nuclear DNA is enclosed by the nuclear envelope.

Extra context: Outside context: 'No nucleus' does NOT mean prokaryotes lack DNA. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

25. What is the main function of the bacterial cell wall?

Answer: It provides structural support/shape and helps protect the cell from osmotic stress.

Extra context: Outside context: Peptidoglycan forms a mechanically strong network around the cell. NCBI Bookshelf describes it as resisting internal osmotic pressure and helping determine shape. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

26. What is peptidoglycan?

Answer: A bacterial cell-wall polymer made of a disaccharide-based glycan backbone cross-linked by short peptides.

Extra context: Outside context: The two sugars are NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid). NCBI Bookshelf describes alternating NAG/NAM chains cross-linked by peptides. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

27. What are the two repeating sugars in the glycan portion of peptidoglycan?

Answer: NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid).

Extra context: Outside context: The lecture diagram shows the disaccharide and peptide cross-linking; NCBI confirms the alternating NAG/NAM backbone. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

28. What gives peptidoglycan its strength?

Answer: Cross-linking between glycan strands by short peptide chains creates a strong network/sacculus around the cell.

Extra context: Outside context: This network resists osmotic pressure and helps maintain bacterial shape. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

29. How does penicillin affect bacterial cell-wall synthesis?

Answer: The lecture says penicillin inhibits transpeptidase, the enzyme that catalyzes peptide cross-linking in peptidoglycan.

Extra context: Outside context: Blocking cross-linking weakens the cell wall and interferes with bacterial growth. NCBI Bookshelf confirms this mechanism. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

30. How does vancomycin affect peptidoglycan synthesis according to the lecture?

Answer: It binds D-Ala and blocks cross-bridge formation.

Extra context: Outside context: The key exam idea is that vancomycin interferes with peptidoglycan assembly by binding its D-Ala-containing precursor. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

31. What is the plasma membrane's primary function?

Answer: It is a selective barrier enclosing the intracellular space and controlling transport into and out of the cell.

Extra context: Outside context: Membrane proteins provide channels, carriers, receptors, and other functions; membrane composition varies among species. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

32. Where are glycoproteins and glycolipids located on the plasma membrane according to the lecture?

Answer: On the extracellular side of the plasma membrane.

Extra context: Outside context: Their carbohydrate portions face the extracellular environment and can contribute to recognition/interactions. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

33. What is a bacterial flagellum made of, and how does it move the cell?

Answer: It is made largely of the protein flagellin; the flagellum rotates like a molecular motor to produce movement.

Extra context: Outside context: The lecture states that the energy source is the proton motive force. Do not confuse bacterial flagella with eukaryotic cilia/flagella, which use a different molecular architecture. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

34. What powers the rotation of a bacterial flagellum in this lecture?

Answer: The proton motive force.

Extra context: Outside context: Ion flow across the membrane drives the flagellar motor. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

35. What are fimbriae?

Answer: Short, numerous, bristle-like protein appendages used primarily for attachment to other cells or surfaces.

Extra context: Outside context: Fimbriae are especially important for adherence, which can contribute to colonization and virulence. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

36. What are pili?

Answer: Longer, generally less numerous protein appendages extending outward from the cell surface; they can function in attachment.

Extra context: Outside context: A specialized sex pilus participates in bacterial conjugation. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

37. What is a sex pilus and what process does it facilitate?

Answer: It facilitates DNA transfer between bacterial cells during conjugation.

Extra context: Outside context: Conjugation is horizontal gene transfer; it can move plasmid DNA between cells. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

38. Why are pili and fimbriae important in bacterial infection?

Answer: They help bacteria adhere to host cells and surfaces, which can promote infectivity and virulence.

Extra context: Outside context: Attachment is often an early step in colonization; not every pilus/fimbria has exactly the same function. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

39. What is the bacterial cytoskeleton?

Answer: A set of intracellular protein filaments that helps control cell shape, cell division, movement, and chromosome/plasmid organization.

Extra context: Outside context: The lecture highlights FtsZ and MreB as bacterial cytoskeletal proteins. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

40. What is FtsZ and what is its major function?

Answer: FtsZ is a tubulin-like cytoskeletal protein involved in bacterial cell division.

Extra context: Outside context: FtsZ forms a division-associated structure at the future division site. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

41. What is MreB and what functions are associated with it?

Answer: MreB is an actin-like bacterial cytoskeletal protein involved in maintaining cell shape and plasmid segregation.

Extra context: Outside context: Think 'MreB = bacterial actin-like shape system.' Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

42. Why can transcription and translation be coupled in prokaryotes?

Answer: Because prokaryotes lack a nucleus, newly made RNA does not have to cross a nuclear envelope before ribosomes can translate it.

Extra context: Outside context: In eukaryotes, transcription occurs in the nucleus while translation occurs in the cytoplasm, so the two processes are spatially separated. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

43. What does it mean for transcription and translation to be 'coupled'?

Answer: Translation can begin on an mRNA while that same mRNA is still being transcribed from DNA.

Extra context: Outside context: This allows rapid gene expression and is possible because there is no nuclear membrane separating the processes. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

44. Why can protein secretion also be closely coupled to protein synthesis in prokaryotes?

Answer: Because there is no nucleus separating transcription from translation, and membrane-associated secretion machinery can interact with newly synthesized proteins as they emerge from ribosomes.

Extra context: Outside context: The lecture's main required reason is the absence of a nucleus and spatial separation. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

45. What is one consequence of coupled gene expression in prokaryotes?

Answer: Gene expression can occur very rapidly because transcription, translation, and related processes are not separated by a nucleus.

Extra context: Outside context: The lecture notes that some bacteria can replicate in about 10 minutes under favorable conditions. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

46. What are the defining structural features of Gram-positive bacteria?

Answer: A thick peptidoglycan cell wall surrounding a plasma membrane; they stain dark purple in a Gram stain.

Extra context: Outside context: NCBI/OpenStax also describe Gram-positive bacteria as lacking the Gram-negative outer membrane and often containing teichoic acids. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

47. What are the defining structural features of Gram-negative bacteria?

Answer: A plasma (inner) membrane, a thin peptidoglycan layer, and an outer membrane containing LPS; they stain light pink/red in a Gram stain.

Extra context: Outside context: OpenStax and NCBI confirm that the peptidoglycan is thinner in Gram-negative bacteria and lies between the inner and outer membranes. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

48. What is the biggest structural difference between Gram-positive and Gram-negative cell envelopes?

Answer: Gram-positive: thick peptidoglycan and no outer membrane. Gram-negative: thin peptidoglycan plus an additional outer membrane.

Extra context: Outside context: The Gram-negative outer membrane contains lipopolysaccharide (LPS) and creates a periplasmic space around the thin peptidoglycan layer. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

49. Which Gram type stains purple, and which stains pink/red?

Answer: Gram-positive = purple. Gram-negative = pink/red.

Extra context: Outside context: The difference comes from how the cell envelope interacts with the Gram-staining procedure. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

50. Where is peptidoglycan located in Gram-positive vs. Gram-negative bacteria?

Answer: Gram-positive: a thick layer outside the plasma membrane. Gram-negative: a thin layer between the inner/plasma membrane and outer membrane.

Extra context: Outside context: This is one of the highest-yield diagrams to be able to draw from memory. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

51. What is LPS and where is it found?

Answer: LPS (lipopolysaccharide) is a major component of the Gram-negative outer membrane.

Extra context: Outside context: LPS is not a component of the Gram-positive wall. Its lipid A portion is associated with endotoxin activity in many Gram-negative bacteria. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

52. What is the periplasmic space?

Answer: The region between the inner/plasma membrane and the outer membrane of Gram-negative bacteria; the thin peptidoglycan layer is located within this envelope.

Extra context: Outside context: OpenStax describes the peptidoglycan layer as sandwiched between the two membranes. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

53. Why does Gram-positive bacteria generally retain the crystal-violet complex better than Gram-negative bacteria?

Answer: The thick peptidoglycan layer of Gram-positive bacteria helps retain the crystal-violet/iodine complex during the decolorization step, whereas Gram-negative cells have a thinner peptidoglycan layer and an outer membrane that is disrupted during staining.

Extra context: Outside context: This explains the purple vs. pink outcome rather than treating the colors as arbitrary facts. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

54. IMPORTANT LECTURE CHECK: Does the slide's line saying Gram-negative bacteria have 'thick peptidoglycan' agree with the diagram and standard references?

Answer: No. The slide text appears inconsistent: it lists 'thick peptidoglycan,' but the diagram and standard references show Gram-negative bacteria have a THIN peptidoglycan layer plus an outer membrane.

Extra context: Outside context: OpenStax and NCBI both confirm thin peptidoglycan for Gram-negative bacteria. For conceptual understanding, memorize THIN + OUTER MEMBRANE. If your professor tests the exact slide wording, be aware of this discrepancy. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

55. What happened to the internal photosynthetic membranes of cyanobacteria according to the lecture?

Answer: They resulted from invagination/folding of the plasma membrane and increase the membrane surface available for photosynthesis.

Extra context: Outside context: Cyanobacteria are photosynthetic bacteria; their internal thylakoid membranes are not membrane-bound organelles like chloroplasts. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

56. How do bacterial and archaeal cell walls differ?

Answer: Bacterial cell walls contain peptidoglycan. Archaeal cell walls do not contain peptidoglycan.

Extra context: Outside context: Archaeal walls can be made from other materials, including proteins, glycoproteins, polysaccharides, or pseudopeptidoglycan depending on the group. Outside source: OpenStax Biology 2e, §22.2.

57. How do bacterial and archaeal membrane lipids differ?

Answer: Lecture comparison: bacteria have ester-linked, unbranched fatty acids attached to D-glycerol; archaea have ether-linked, branched lipids associated with L-glycerol.

Extra context: Outside context: The unusual ether-linked, branched archaeal lipids contribute to membrane stability under extreme conditions. Outside source: OpenStax Biology 2e, §22.2.

58. Why are archaeal membranes especially useful in extreme environments?

Answer: Ether linkages are more chemically stable than ester linkages; branched hydrocarbon groups reduce movement; and tetraether lipids can span the membrane to form a monolayer, making it more rigid/stable.

Extra context: Outside context: The lecture specifically connects these features with survival in high-temperature environments such as hot springs and ocean vents. Outside source: OpenStax Biology 2e, §22.2.

59. What is special about tetraether lipids in some archaeal membranes?

Answer: They can span the membrane and form a lipid monolayer rather than a conventional bilayer, increasing membrane rigidity/stability.

Extra context: Outside context: This is particularly useful under high-temperature conditions. Outside source: OpenStax Biology 2e, §22.2.

60. How do bacterial vs. archaeal ribosomes compare according to the lecture?

Answer: Bacterial ribosomes are described as bacteria-like; archaeal ribosomes are more eukaryotic-like.

Extra context: Outside context: Many components of archaeal information-processing machinery (transcription/translation) are more similar to eukaryotes than to bacteria. Outside source: OpenStax Biology 2e, §22.2.

61. How do bacterial vs. archaeal tRNAs compare according to the lecture?

Answer: Bacterial tRNAs are described as bacteria-like; archaeal tRNAs are described as eukaryotic-like.

Extra context: Outside context: The lecture is emphasizing the broader molecular relationship between Archaea and Eukarya. Outside source: OpenStax Biology 2e, §22.2.

62. What are the two major lipid-linkage types you must distinguish for Bacteria vs. Archaea?

Answer: Bacteria: ester linkages. Archaea: ether linkages.

Extra context: Memory hook: Bacteria = ESTER; Archaea = ETHER. Then add the second distinction: bacterial lipids are typically unbranched, archaeal lipids often branched. Outside source: OpenStax Biology 2e, §22.2.

63. What are the three major domains/lineages of life?

Answer: Bacteria, Archaea, and Eukarya.

Extra context: Outside context: The lecture calls these the three major lineages; modern biology commonly refers to the three domains of life. Outside source: OpenStax Biology 2e, §22.2.

64. What is the endosymbiotic explanation for the origin of eukaryotic cells presented in this lecture?

Answer: Eukaryotes resulted from endosymbiosis involving an archaeal host and a bacterial endosymbiont.

Extra context: Outside context: The lecture specifically states that mitochondria evolved from a Proteobacteria-like endosymbiont and chloroplasts from a Cyanobacteria-like endosymbiont. Outside source: OpenStax Biology 2e, §22.2.

65. What bacterial lineage is proposed as the ancestor of mitochondria?

Answer: A Proteobacteria-like endosymbiont.

Extra context: Outside context: This is the specific association given on the lecture slide. Outside source: OpenStax Biology 2e, §22.2.

66. What bacterial lineage is proposed as the ancestor of chloroplasts?

Answer: A Cyanobacteria-like endosymbiont.

Extra context: Outside context: Cyanobacteria are photosynthetic bacteria, fitting the photosynthetic function of chloroplasts. Outside source: OpenStax Biology 2e, §22.2.

67. A spherical cell doubles its radius. Does its surface area or volume increase more dramatically, and what happens to SA:V?

Answer: Volume increases more dramatically because V ∝ r³ while SA ∝ r². Therefore SA:V decreases.

Extra context: Use this to reason through unfamiliar numbers instead of memorizing a single example. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

68. A bacterium has no nucleus. A ribosome begins translating an mRNA while RNA polymerase is still making that mRNA. Is this possible? Explain.

Answer: Yes. In prokaryotes, transcription and translation can be coupled because there is no nucleus/nuclear envelope separating them.

Extra context: This is a classic application of the 'no nucleus → no spatial separation' rule. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

69. You observe purple spherical bacteria arranged in grape-like clusters. What morphology and Gram type are suggested by the lecture?

Answer: Staphylococcus-like arrangement: cocci in clusters. If the cells are purple after Gram staining, they are Gram-positive.

Extra context: Don't confuse shape/arrangement with Gram reaction: 'coccus' describes shape; purple describes Gram-positive staining. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

70. You observe pink rod-shaped bacteria with an outer membrane. What are the likely morphology and Gram classification?

Answer: Bacillus/rod-shaped and Gram-negative.

Extra context: The key clues are rod shape + pink Gram stain + outer membrane. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

71. A drug prevents transpeptidase from forming peptide cross-links in peptidoglycan. What happens to the bacterial cell wall?

Answer: Peptidoglycan cross-linking is weakened, reducing cell-wall strength and interfering with bacterial growth.

Extra context: This is the mechanism highlighted for penicillin in the lecture. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

72. A mutation removes FtsZ from a bacterium. Which process would be most directly affected?

Answer: Cell division.

Extra context: Lecture association: FtsZ = tubulin-like; cell division. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

73. A mutation disrupts MreB. Which functions would you predict are affected?

Answer: Cell-shape maintenance and plasmid segregation, based on the lecture.

Extra context: Lecture association: MreB = actin-like; shape + plasmid segregation. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

74. A bacterium loses its fimbriae. What cellular ability is most directly reduced?

Answer: Attachment/adherence to other cells or surfaces.

Extra context: Attachment can influence colonization and virulence. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

75. A bacterial cell has a thick peptidoglycan wall but no outer membrane. It stains purple. Gram-positive or Gram-negative?

Answer: Gram-positive.

Extra context: Use the structural pattern rather than memorizing organism names. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

76. A bacterial cell has a thin peptidoglycan layer between an inner membrane and an outer LPS-containing membrane. Gram-positive or Gram-negative?

Answer: Gram-negative.

Extra context: This is the core Gram-negative envelope diagram. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

77. Why would an enzyme that breaks peptidoglycan potentially damage bacterial cells?

Answer: Peptidoglycan provides mechanical strength and protects bacteria from osmotic stress. Breaking it weakens the cell wall and can lead to loss of structural integrity.

Extra context: The lecture's final discussion uses lysozyme as the example. NCBI also describes peptidoglycan as a stress-bearing layer. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

78. Why might lysozyme be more effective against Gram-positive bacteria than Gram-negative bacteria?

Answer: Gram-positive peptidoglycan is exposed outside the plasma membrane, while Gram-negative bacteria have an additional outer membrane that can limit access to the peptidoglycan layer.

Extra context: This is the reasoning expected by the lecture's final discussion question. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

79. Why are lysozyme and other antibacterial defenses useful in tears?

Answer: Tears form part of the body's protective surface defenses and contain lysozyme, which can degrade bacterial peptidoglycan.

Extra context: The lecture specifically asks why lysozyme is found in tears and egg whites; the broad idea is antimicrobial protection. Outside source: NCBI Bookshelf, Cell Walls and the Extracellular Matrix / Essentials of Glycobiology.

80. A student says, 'Prokaryotes are simple because they don't have membrane-bound organelles.' How would you respond using this lecture?

Answer: Lack of membrane-bound organelles does not mean lack of complexity. Prokaryotes have organized DNA in a nucleoid, ribosomes, cell walls/membranes, flagella, pili/fimbriae, cytoskeletal proteins, complex cell-envelope chemistry, and tightly coupled gene expression.

Extra context: The lecture's discussion slide explicitly asks you to evaluate whether prokaryotes are 'simple' or 'complex.' A strong answer distinguishes organizational simplicity from molecular/functional complexity. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

81. Which structure would you target if you wanted to stop bacterial motility without directly destroying the plasma membrane?

Answer: The flagellum/flagellar motor.

Extra context: Lecture: bacterial flagella rotate using a proton motive force. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

82. Which structure is most directly responsible for selective movement of substances into and out of a bacterial cell?

Answer: The plasma membrane.

Extra context: The cell wall provides support/protection; the plasma membrane is the selective transport barrier. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

83. If a cell's SA:V becomes too low, what two broad strategies could improve exchange?

Answer: Reduce cell size/divide, or increase effective surface area (for example through folding or elongated/flattened shapes).

Extra context: Outside context: These strategies follow directly from the geometry of SA:V. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

84. What is the single best way to distinguish Bacteria from Archaea on a cell-envelope question?

Answer: Ask: 'Is peptidoglycan present?' Bacteria have peptidoglycan; Archaea do not. Then check membrane chemistry: bacteria mainly ester-linked lipids; archaea ether-linked, branched lipids.

Extra context: This is a high-yield two-step decision rule for unfamiliar diagrams. Outside source: OpenStax Biology 2e, §22.2.

85. From the typical bacterial-cell diagram, what structures should you be able to identify?

Answer: Capsule (if present), cytoplasm, ribosomes, nucleoid, plasma/cell membrane, cell wall/peptidoglycan, flagellum, and—in some cells—pili/fimbriae.

Extra context: The lecture's page 8 diagram labels these structures. Practice drawing a generic bacterium and labeling them without notes. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

86. What is the difference between a capsule and a cell wall?

Answer: The cell wall is a structural layer outside the plasma membrane; a capsule, when present, is an additional outer coating outside the cell wall.

Extra context: Outside context: Capsules can help attachment and can protect against dehydration and immune attack. Source: OpenStax Biology 2e, §22.2. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

87. Are flagella, capsules, and pili found in every prokaryote?

Answer: No. They are optional/accessory structures found in some prokaryotes.

Extra context: Outside context: OpenStax explicitly notes that flagella, capsules, and pili are not found in all prokaryotes. Outside source: OpenStax Biology 2e, §§4.2 and/or 22.2.

88. What does 'prokaryote' literally refer to in terms of cell organization?

Answer: It refers to cells without a membrane-bound nucleus; their DNA is located in a nucleoid region.

Extra context: Outside context: 'Pro-' means before and '-kary-' refers to nucleus, but the modern biological definition is based on cell organization rather than a literal evolutionary claim that the cells are 'before nuclei.' Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

89. What does 'eukaryote' refer to in terms of cell organization?

Answer: A cell with a membrane-bound nucleus and membrane-bound organelles.

Extra context: Outside context: Animals, plants, fungi, and protists are eukaryotic. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.

90. Can you answer every learning outcome from Lecture 6 without notes? What must you be able to do?

Answer: You should be able to: (1) state cell theory; (2) explain low/high cell-size limits using SA:V; (3) match microscopy methods to their purposes; (4) distinguish prokaryotes/eukaryotes; (5) identify bacterial morphology/arrangements; (6) explain nucleoid, cell wall, plasma membrane, flagella, pili/fimbriae, cytoskeleton; (7) explain coupled transcription/translation/protein secretion; (8) describe peptidoglycan; (9) compare Gram+ vs Gram−; (10) compare Bacteria vs Archaea; (11) explain archaeal extreme-environment adaptations; (12) explain the three major lineages and endosymbiotic origins.

Extra context: This card is intentionally a checklist: if you cannot answer any item aloud, flag the relevant tagged cards and review them. Outside context: based primarily on the uploaded Lecture 6 slides; enrichment is clearly labeled.