Question 1

Which of the following best explains why Archaea are classified as prokaryotes, yet are genetically more similar to eukaryotes than to bacteria?

Accepted Answer

Archaea lack a nucleus and membrane-bound organelles, but their ribosomal RNA sequences are more similar to eukaryotes.

Question 2

Which of the following statements about Gram-positive and Gram-negative bacteria is correct?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and contain teichoic acids, while Gram-negative bacteria have an outer membrane and a thin peptidoglycan layer.

Question 3

A patient is prescribed an antibiotic that targets prokaryotic ribosomes. Why is this treatment effective against bacteria but not harmful to human cells?

Accepted Answer

Prokaryotic ribosomes are 70S, while eukaryotic ribosomes are 80S, so the antibiotic selectively targets bacterial protein synthesis.

Question 4

Which of the following best describes the process of osmosis in a bacterial cell placed in a hypertonic solution?

Accepted Answer

Water moves out of the cell, causing plasmolysis.

Question 5

Which of the following is a key reason why biochemical tests are important in microbiology?

Accepted Answer

They allow identification of microorganisms based on their metabolic activities.

Question 6

Louis Pasteur’s swan neck flask experiment disproved which scientific theory?

Accepted Answer

Spontaneous generation

Question 7

Which of the following best describes the binomial system of nomenclature introduced by Carolus Linnaeus?

Accepted Answer

Each organism is given a two-part Latin name consisting of the genus and species.

Question 8

Which of the following is a major function of resident microbiota in the human gut?

Accepted Answer

They help digest food and protect against pathogenic bacteria.

Question 9

Why are viruses not included in phylogenetic trees?

Accepted Answer

Viruses are acellular and lack ribosomal RNA, making them difficult to classify genetically.

Question 10

Which of the following best explains the endosymbiotic theory?

Accepted Answer

Eukaryotic cells originated from prokaryotic cells engulfing other prokaryotes, which became organelles.

Question 11

Which bacterial genus is known for producing endospores, and why are endospores important?

Accepted Answer

Bacillus; endospores allow survival in harsh conditions.

Question 12

Which of the following best describes the difference between simple diffusion and active transport across a cell membrane?

Accepted Answer

Simple diffusion does not require energy, while active transport requires ATP.

Question 13

Which of the following is a correct statement about the structure of DNA?

Accepted Answer

DNA is composed of nucleotides linked by phosphodiester bonds, with bases held together by hydrogen bonds.

Question 14

A cell is placed in an isotonic solution. What will happen to the cell?

Accepted Answer

There will be no net movement of water; the cell remains unchanged.

Question 15

Which of the following best describes the function of NAD$$^+$$ and FAD in cellular respiration?

Accepted Answer

They act as electron carriers, transporting electrons to the electron transport chain.

Question 16

Which of the following is true regarding glycolysis in prokaryotic and eukaryotic cells?

Accepted Answer

Glycolysis occurs in the cytoplasm in both prokaryotic and eukaryotic cells.

Question 17

Which of the following best describes competitive inhibition of an enzyme?

Accepted Answer

A molecule similar to the substrate binds to the active site, preventing substrate binding.

Question 18

Which of the following is a correct application of Chargaff’s rules to a DNA sample with 30% adenine?

Accepted Answer

The sample will have 30% thymine, and 20% cytosine and guanine each.

Question 19

Which of the following best explains why Alcanivorax borkumensis is important in environmental microbiology?

Accepted Answer

It degrades hydrocarbons and is used in bioremediation of oil spills.

Question 20

A bacterial culture starts with 100 cells and doubles every hour. How many cells will there be after 5 hours? Use the formula $$N = N_0$ 	imes 2^n$$, where $$N_0 is $$the initial number of cells and $$n is $$the number of generations.

Accepted Answer

3200

Comprehensive Study Guide for Microbiology Exam #1

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