Unit 3: Cell Structure, function, microbial growth and nutrition - Practice Quiz

1 Which of the following is a defining feature of prokaryotic cells?

2 The typical size range of most bacterial cells is:

3 Which appendage is primarily responsible for bacterial motility?

4 A well-organized layer of polysaccharide firmly attached to the cell wall is called a:

5 Short, hair-like appendages used mainly for attachment to surfaces are known as:

6 Which technique is commonly used to obtain isolated bacterial colonies on a solid medium?

7 The solidifying agent most commonly used in microbiological culture media is:

8 The bacterial plasma membrane is primarily composed of:

9 Which structures in the bacterial cytoplasm are the sites of protein synthesis?

10 The sedimentation coefficient of a bacterial ribosome is:

11 The region in a bacterial cell where the chromosome is located is called the:

12 Plasmids are best described as:

13 The bacterial chromosome is typically:

14 The main structural polymer of the bacterial cell wall is:

15 Gram-positive bacteria are characterized by a cell wall containing:

16 A key difference of archaeal cell walls compared with bacterial ones is that archaea:

17 Organisms that use light as their energy source are called:

18 Microorganisms that use as their main carbon source are termed:

19 A medium that favors the growth of certain microorganisms while inhibiting others is called a:

20 Freeze-drying (lyophilization) preserves microbial cultures by:

21 A researcher observes a bacterium that lacks membrane-bound organelles but efficiently carries out aerobic respiration. Where are the electron transport chain components most likely located?

22 Which feature best distinguishes a prokaryotic cell from a eukaryotic cell at the structural level?

23 A pathogenic bacterium resists phagocytosis by host immune cells. Which external structure is most likely responsible for this protection?

24 A bacterium shows rapid directional movement toward a nutrient source. Which appendage and mechanism explains this behavior?

25 To obtain isolated colonies from a mixed bacterial sample on a single agar plate, which technique is most appropriate?

26 MacConkey agar allows growth of Gram-negative bacteria while inhibiting Gram-positive ones and distinguishes lactose fermenters by color. This medium is best classified as:

27 Unlike bacteria, the plasma membranes of many archaea contain lipids linked by which type of bond, giving them heat stability?

28 Inclusion bodies such as poly--hydroxybutyrate (PHB) granules in the cytoplasmic matrix primarily function to:

29 A bacterial strain acquires antibiotic resistance that can be transferred to another cell during conjugation. This trait is most likely carried on a:

30 The bacterial nucleoid differs from a eukaryotic nucleus mainly because it:

31 A Gram-positive bacterium retains crystal violet after decolorization. This is due to its cell wall having:

32 Archaeal cell walls differ from bacterial walls because archaea:

33 An organism that uses light as its energy source and as its carbon source is classified as a:

34 A bacterium oxidizes inorganic ammonia for energy and fixes for carbon. Its nutritional type is:

35 Which element is required by microbes primarily for the synthesis of nucleic acids and phospholipids?

36 A microbiologist needs a solidifying agent for culture media that most bacteria cannot degrade and that remains solid at incubation temperatures. The best choice is:

37 A defined (synthetic) medium is characterized by:

38 For long-term storage of cultures at approximately , which method offers the highest viability and genetic stability?

39 A cryoprotectant such as glycerol is added before freezing cultures primarily to:

40 During freeze-drying (lyophilization), water is removed from a frozen culture mainly by:

41 A researcher analyzes the peptidoglycan of a bacterium and finds that the interpeptide bridge consists of five glycine residues linking the tetrapeptides. In another organism, direct cross-linking occurs between DAP and D-alanine with no bridge. Which conclusion is most accurate regarding these two organisms?

42 Archaeal cell walls differ fundamentally from bacterial walls. Which combination of features would you expect in an archaeon but never in a true bacterium?

43 Certain thermoacidophilic archaea maintain membrane integrity at temperatures above and pH near 1. Which membrane adaptation best explains this stability?

44 An organism obtains energy from oxidizing , uses as its carbon source, and derives electrons from the same inorganic sulfur compound. How is this organism classified?

45 Purple non-sulfur bacteria can grow using light for energy while using organic compounds as their carbon source. When light is absent but oxygen is present, they switch to aerobic respiration. Under the anaerobic light condition, their nutritional type is best described as:

46 MacConkey agar contains crystal violet, bile salts, lactose, and neutral red. A colony appears pink/red. Which interpretation combines the medium's selective and differential functions correctly?

47 You need to isolate a single pure colony from a heavily contaminated mixed culture with very high cell density. Which technique provides progressive dilution across a single plate to obtain well-separated colonies?

48 Two plasmids introduced into the same bacterial cell are consistently lost from one another over generations and cannot be stably co-maintained. This phenomenon is due to:

49 The bacterial nucleoid maintains its condensed, supercoiled structure without a nuclear membrane. Which factor is NOT primarily responsible for nucleoid organization?

50 A pathogenic bacterium evades phagocytosis and forms biofilms on medical implants. Electron microscopy shows a well-organized, tightly bound layer of polysaccharide external to the wall, distinct from a loose diffuse layer. This structure is best described as:

51 A motile bacterium is placed in a gradient of attractant. It exhibits runs and tumbles, with runs lengthening toward higher attractant concentration. Which flagellar mechanism underlies a 'run'?

52 Which statement correctly distinguishes a fundamental structural constraint on prokaryotic cell size and metabolism?

53 Gas vacuoles in aquatic cyanobacteria allow buoyancy regulation. Which property of the gas vesicle membrane makes this possible?

54 Inclusion bodies in bacteria serve as storage or functional structures. Which pairing of inclusion body and function is INCORRECT?

55 A microbiologist must grow a fastidious organism whose exact nutritional needs are unknown, requiring reproducible results for a metabolic study. Which choice presents the correct trade-off between chemically defined and complex media?

56 Thioglycollate broth is used to determine an organism's oxygen relationship. An organism grows as a band a few millimeters below the surface. This organism is most likely a:

57 During lyophilization, the order of steps is critical to preserving viability. Which sequence and rationale is correct?

58 Cryoprotectants and lyoprotectants like trehalose or skim milk are added before lyophilization. Their primary protective mechanism is to:

59 Liquid nitrogen storage at is considered the gold standard for long-term preservation. Why is controlled slow cooling with a cryoprotectant like glycerol essential before immersion?

60 For routine short-term maintenance, subculturing (periodic transfer) has a significant disadvantage compared with liquid nitrogen or lyophilization. Which risk is most associated with repeated subculturing?