Question 1

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

Accepted Answer

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

Question 2

A patient is diagnosed with a bacterial infection caused by an obligate anaerobe. Which of the following best explains why this organism cannot survive in the presence of oxygen?

Accepted Answer

Obligate anaerobes lack enzymes such as superoxide dismutase and catalase, which detoxify reactive oxygen species.

Question 3

Which of the following best describes the process and purpose of the polymerase chain reaction (PCR)?

Accepted Answer

PCR is used to amplify specific DNA sequences using cycles of denaturation, annealing, and extension.

Question 4

Which of the following is a unique feature of Archaea compared to Bacteria and Eukarya?

Accepted Answer

Archaea have membrane lipids with ether bonds rather than ester bonds.

Question 5

A microbiologist is testing the effectiveness of a new disinfectant. Which of the following methods would be most appropriate to evaluate the disinfectant's ability to kill endospores?

Accepted Answer

Use the disinfectant on a culture of Bacillus subtilis spores and assess for growth.

Question 6

Which of the following best explains why viruses are not classified within the three domains of life?

Accepted Answer

Viruses lack cellular structure and do not possess ribosomes for protein synthesis.

Question 7

During glycolysis, what is the net gain of ATP molecules per molecule of glucose metabolized?

Accepted Answer

$$2$$

Question 8

Which of the following statements about the complement system is correct?

Accepted Answer

The complement system can be activated by the classical, alternative, and lectin pathways, all leading to the formation of the membrane attack complex (MAC).

Question 9

A patient receives a kidney transplant and is prescribed immunosuppressive drugs. Which immune cells are primarily responsible for transplant rejection if the drugs are not taken?

Accepted Answer

Cytotoxic T cells ($$T_C$$ cells)

Question 10

Which of the following best describes the difference between endotoxins and exotoxins?

Accepted Answer

Endotoxins are part of the outer membrane of Gram-negative bacteria and are released upon cell death, while exotoxins are secreted proteins produced by both Gram-positive and Gram-negative bacteria.

Question 11

Which of the following is a correct sequence of events in the lytic cycle of a bacteriophage?

Accepted Answer

Attachment, penetration, biosynthesis, maturation, release

Question 12

Which of the following best describes the role of antigen-presenting cells (APCs) in adaptive immunity?

Accepted Answer

APCs process and present antigens on major histocompatibility complex (MHC) molecules to T cells, initiating the adaptive immune response.

Question 13

Which of the following is a characteristic of a live attenuated vaccine?

Accepted Answer

It contains a weakened form of the pathogen that can replicate but does not cause disease in healthy individuals.

Question 14

Which of the following best explains why biofilms are more resistant to antimicrobial agents than planktonic (free-living) bacteria?

Accepted Answer

Biofilms have an extracellular polymeric substance (EPS) matrix that limits penetration of antimicrobials and facilitates exchange of resistance genes.

Question 15

Which of the following best describes the function of B cells in the immune system?

Accepted Answer

B cells differentiate into plasma cells that secrete antibodies specific to antigens.

Question 16

A laboratory technician is using the ELISA test to detect the presence of HIV antibodies in a patient's serum. Which principle does this test rely on?

Accepted Answer

Specific binding between antigen and antibody, detected by an enzyme-linked indicator.

Question 17

Which of the following is a correct statement about the structure of DNA in bacteria compared to humans?

Accepted Answer

Bacterial DNA is typically a single circular chromosome, while human DNA is organized into multiple linear chromosomes.

Question 18

Which of the following best describes the difference between respiration and fermentation in bacteria?

Accepted Answer

Respiration uses an electron transport chain and a final electron acceptor (such as $$O_2$$), producing more ATP, while fermentation does not use an electron transport chain and produces less ATP.

Question 19

Which of the following is a correct statement about the cardinal temperatures for microbial growth?

Accepted Answer

Cardinal temperatures refer to the minimum, optimum, and maximum temperatures at which a microorganism can grow.

Comprehensive Study Notes for Microbiology Final Exam (Biology 221)

Study Guide - Practice Questions

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