Question 1

A nurse observes that an intravenous (I.V.) solution appears turbid before administration. What is the most likely reason for this turbidity, and why was the nurse's decision to withhold the solution correct?

Accepted Answer

Turbidity indicates the presence of microbial contamination, which could cause infection if administered; withholding the solution prevents introducing pathogens into the patient's bloodstream.

Question 2

A urine specimen is collected with 1,000 bacterial cells/mL but is left at room temperature for 4 hours before being sent to the lab. How might this affect the diagnosis of a urinary tract infection (UTI)?

Accepted Answer

Bacterial cells may multiply during the delay, potentially leading to a false-positive diagnosis of UTI.

Question 3

Which of the following is NOT a method for measuring microbial growth discussed in lecture?

Accepted Answer

Gram staining and microscopic observation

Question 4

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization destroys all forms of microbial life, including spores, while disinfection eliminates most pathogens but not necessarily spores.

Question 5

Which of the following is a specific example of sterilization?

Accepted Answer

Autoclaving surgical instruments at $121^{\circ}C$ for 15 minutes to destroy all microbes and spores.

Question 6

Which of the following factors should NOT be considered when choosing a disinfectant for hospital use?

Accepted Answer

The color of the disinfectant solution

Question 7

Why are Mycobacterium species harder to kill with disinfectants than most other microbes?

Accepted Answer

They have a waxy, lipid-rich cell wall that resists penetration by many disinfectants.

Question 8

Which of the following terms describes the process of reducing the number of pathogens on living tissue, and what is a common example?

Accepted Answer

Antisepsis; using iodine to clean a wound before surgery.

Question 9

Which statement correctly compares the structure and function of DNA and RNA?

Accepted Answer

DNA is double-stranded and stores genetic information; RNA is usually single-stranded and functions in protein synthesis.

Question 10

What is the function of tRNA during translation?

Accepted Answer

tRNA carries specific amino acids to the ribosome and matches its anticodon to the mRNA codon.

Question 11

Genes are made of which type of molecule, and what do they code for?

Accepted Answer

Genes are made of DNA and code for proteins.

Question 12

If genes only encode proteins, how do microbes synthesize non-protein molecules such as phospholipids?

Accepted Answer

Enzymes encoded by genes catalyze the synthesis of non-protein molecules from precursor molecules.

Question 13

Where do transcription and translation occur in prokaryotic cells?

Accepted Answer

Both transcription and translation occur in the cytoplasm.

Question 14

A DNA strand has the sequence $5'	ext{-}ATG\,GCC\,TAA	ext{-}3'$. What is the corresponding mRNA sequence produced during transcription?

Accepted Answer

$5'	ext{-}AUG\,GCC\,UAA	ext{-}3'$

Question 15

Given the mRNA sequence $5'	ext{-}AUG\,GCC\,UAA	ext{-}3'$, what is the amino acid sequence of the resulting polypeptide chain?

Accepted Answer

Methionine - Alanine

Question 16

Which of the following best describes pasteurization?

Accepted Answer

A process that uses mild heat to reduce the number of pathogens in food and beverages, such as heating milk at $72^{\circ}C$ for 15 seconds.

Question 17

Which of the following is an example of degerming?

Accepted Answer

Using an alcohol swab to clean the skin before an injection.

Question 18

A hospital is deciding between two disinfectants. Disinfectant A is highly effective but toxic to humans, while Disinfectant B is less effective but safe. Which factor is most important in this decision?

Accepted Answer

The safety of the disinfectant for human use in the hospital environment.

Question 19

Which of the following best describes a codon?

Accepted Answer

A sequence of three nucleotides in mRNA that specifies a particular amino acid.

Microbiology Study Guide: Microbial Growth, Control, and Genetics

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