Question 1

Which of the following statements best explains why Archaea are considered more closely related to Eukaryotes than to Bacteria, despite being prokaryotic?

Accepted Answer

Archaea share similar ribosomal RNA sequences with Eukaryotes.

Question 2

A patient is prescribed an antibiotic that targets 70S ribosomes. Why does this antibiotic selectively harm bacteria but not human cells?

Accepted Answer

Bacterial ribosomes are 70S, while eukaryotic ribosomes are 80S.

Question 3

Which of the following best describes the function of teichoic acids in Gram-positive bacteria and their relevance to MRSA (Methicillin-resistant Staphylococcus aureus)?

Accepted Answer

Teichoic acids help anchor the cell wall and contribute to the pathogenicity of MRSA.

Question 4

Which of the following best explains why viruses are not included in phylogenetic trees of life?

Accepted Answer

Viruses lack cellular structure and do not share a common ancestor with cellular life.

Question 5

A bacterial cell is placed in a hypertonic solution. What is the most likely outcome, and which process is responsible?

Accepted Answer

The cell will lose water and shrink (plasmolysis) due to osmosis.

Question 6

Which of the following best describes the main difference between Gram-positive and Gram-negative bacterial cell walls?

Accepted Answer

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

Question 7

Which of the following is a correct representation of the dehydration synthesis reaction that forms a peptide bond between two amino acids?

Accepted Answer

$$\mathrm{Amino\ acid\ 1\ +\ Amino\ acid\ 2\ \rightarrow\ Dipeptide\ +\ H_2O}$$

Question 8

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 9

Which of the following best describes the process and significance of Louis Pasteur’s swan neck flask experiment?

Accepted Answer

It disproved spontaneous generation by showing that microorganisms did not grow in broth unless exposed to air.

Question 10

Which of the following is a correct statement about the endosymbiotic theory?

Accepted Answer

It proposes that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

Question 11

A bacterial culture starts with 100 cells and has a generation time of 30 minutes. How many cells will there be after 3 hours, assuming exponential growth and no cell death? Use the formula $$N = N_0$ 	imes 2^n$$, where $$n is $$the number of generations.

Accepted Answer

$$N = 100 	imes 2^6$ = 6,400$$

Question 12

Which of the following best describes the difference between competitive and non-competitive enzyme inhibition?

Accepted Answer

Competitive inhibitors resemble the substrate and bind to the active site; non-competitive inhibitors bind elsewhere and change enzyme shape.

Question 13

Which of the following best explains why resident microbiota in the human gut are beneficial?

Accepted Answer

They aid in digestion, synthesize vitamins, and prevent colonization by pathogens.

Question 14

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

Accepted Answer

The two strands are held together by hydrogen bonds between complementary bases.

Question 15

Which of the following best describes the function of NAD+ in cellular metabolism?

Accepted Answer

NAD+ acts as an electron carrier, accepting electrons during glycolysis and the Krebs cycle.

Question 16

Which of the following best explains why endospores are important for certain bacterial genera such as Bacillus and Clostridium?

Accepted Answer

Endospores allow bacteria to survive harsh environmental conditions such as heat, desiccation, and chemicals.

Question 17

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

Accepted Answer

Facilitated diffusion requires a transport protein, while simple diffusion does not.

Question 18

Which of the following best describes the role of cholesterol in eukaryotic cell membranes?

Accepted Answer

Cholesterol increases membrane fluidity at low temperatures and decreases it at high temperatures.

Question 19

Which of the following best explains the difference between exergonic and endergonic reactions?

Accepted Answer

Exergonic reactions release energy, while endergonic reactions require energy input.

Microbiology Exam 1 Study Guide: Classification, Cell Structure, Biochemistry, Genetics, and Metabolism

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