Microbiology 2124: Exam 2
October 10, 2001
Dr. Babu Z. Fathepure

General Instructions:
Write your name clearly on all pages.
Choose the most correct answer and mark the corresponding letter on your scantron sheet.
Answer the supplement questions on page 7. The supplement-questions page should be detached and returned to the instructor for grading.
The multiple choice questions are worth 3.33 points each.

Multiple Choice Questions:
1. Which of the following processes does not generate ATP?
a) photophosphorylation
b). the Calvin-Bensen cycle
c). oxidative phophorylation
d). substrate-level phosphorylation

2. Which substance in the following fermentative reaction serves as an electron acceptor?

CH3-CHO + NADH + H+

CH3-CH2OH + NAD+

a). acetaldehyde
b). NADH
c). ethanol
d). NAD⁺

3. Most chemoautotrophs generally use substrates such as
a). glucose
b). carbon dioxide
c). oxygen
d). sunlight

4. If there are 10³ cells/ml at the middle of log phase, and the generation time of the cells is 30 minutes, how many cells will there be after 2 hours?
a). 2 x 10³
b). 4 x 10³
c). 8 x 10³
d). 1.6 x 10⁴
Solution à N = N₀ x (2)ⁿ n= t/g
N = 1,000 x 16 n = 120/30
N = 16,000 = 1.6 x 10⁴ n = 4

5. In which of the following four phases of growth curve, are microbes most sensitive to penicillin?
a). phase 1
b). phase 2
c). phase 3
d). phase 4

6. Nutrient broth is an example of a…
a). defined medium
b). complex medium
c). selective medium
d). differential medium

Q. Below is a typical growth curve of bacteria with various stages numbered 1-4. Please answer question 7 and 8 using the following figure.

3

7. Which stage shows a phase where the number of cells dying equals the number of cells dividing?
a). stage 1
b). stage 2
c). stage 3
d). Stage 4

8. Which stages of the graph illustrate a logarithmic change in cell number?
a). 1 and 3
b). 2 and 4
c). 2 and 3
d). 1 and 4

9. Which of the following types of media would not be used to culture aerobic bacteria?
a). differential media
b). enrichment medium
c). reducing media
d). complex media

10. Which of the following is not used to determine metabolic activity?
a). acid production from fermentation
b). CO₂ production from the Krebs cycle
c). oxygen consumption
d). turbidity measurement

11. All of the following are direct methods to measure microbial growth except:
a). microscopic count
b). standard plate count
c). filtration
d). metabolic acivity

12. Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?
a). psychrophiles
b). halophiles
c). thermophiles
d). anaerobes

13. The number of colonies obtained in a plate count does not depend on
a). inoculum size
b). size of the colonies
c). type of culture medium
d). length of incubation

14. Which of the following forms of oxygen are generally toxic to living organisms?
a). superoxide anion
b). hydrogen peroxide
c). hydroxyl radical
d). all of the above

15. Which of the following methods is used to sterilize heat-labile solutions?
a). dry heat
b). autoclave
c). filtration
d). pasteurization

16. Agents that kill bacteria are called
a). inhibitory
b). bactericidal
c). bacteriostatic
d). all of the above

17. The time required for a 10-fold reduction in population density at a given temperature is called the
a). thermal death time
b). decimal reduction time
c). mean strerilization time
d). none of the above

18. The antimicrobial activity of chlorine is due to which of the following?
a). the formation of hypochlorous acid
b). the formation of hydrochloric acid
c). the formation of trihalomethanes
d). the formation of chloride ion

19. Iodophors differ from iodine in that iodophors
a). are combined with an organic molecule for slow release
b). are less irritating
c). are long lasting
d). all of the above

20. Which of the following substances is the least effective antimicrobial agent?
a). soap
b). cationic detergents
c). phenolics
d). alcohol

21. Which concentration of ethyl alcohol is the most bacteriocidal?
a). 100%
b). 70 %
c). 30 %
d). 50 %

22. In the flowing figure, antimicrobial agents were added to exponentially growing cultures at the time shown by an arrow. Which of the lines indicates the addition of a bacteriocidal compound?

23. Which of the following enzymes converts hydrogen peroxide to oxygen and water?
a). oxidase
b). carboxylase
c). catalase
d). polymerase

24. If you determined that the DNA of a species of bacteria was 27% cytosine, you would correctly predict that there is ______% thymine in the DNA.
a). 27%
b) 23%
c). 73%
d). 0%

25. Which of the following pairs is mismatched?
a). DNA polymerase — makes a molecule of DNA from a DNA template
b). RNA polymerase — makes a molecule of RNA from an RNA template
c). RNA polymerase — makes a molecule of RNA in 5’à3’ direction
d). DNA polymerase — makes a molecule of DNA in 5’à3’ direction

26. Which of the following is not a product of transcription?
a). a new strand of DNA
b). rRNA
c). tRNA
d). mRNA

27. A gene is best defined as
a). a segment of DNA
b). three nucleotide that code for an amino acid
c). a sequence of nucleotide in DNA that code for a functional product
d). a sequence of nucleotide in RNA that code for a functional product.

Supplemental Questions
Microbiology 2124: Exam 2
October 10, 2001

1. Fill in the following table with the carbon source and energy source of each type of organism (3 points).

2. There is only one correct answer to each question in right panel; please write the best answer to the question in the left panel (7 points)

3.