Q: A bacterial population doubles every 20 minutes. If you start with 1 bacterium, how many bacteria will there be after 2 hours under ideal conditions? Use the formula $N = N_0 \times 2^{(t/d)}$, where $N_0$ is the initial number, $t$ is time in minutes, and $d$ is the doubling time.

$N = 1 \times 2^{(120/20)} = 1 \times 2^6 = 64$

Question 1

Which of the following statements best explains why antibiotics are ineffective against viral infections such as influenza?

Accepted Answer

Viruses lack the cellular structures targeted by antibiotics, such as cell walls and ribosomes.

Question 2

A patient is diagnosed with a bacterial infection. The bacteria are found to contain plasmids. What is the most significant implication of the presence of plasmids in these bacteria?

Accepted Answer

Plasmids can carry genes for antibiotic resistance, which can be transferred between bacteria.

Question 3

Which of the following best describes the mechanism by which steroid hormones affect target cells?

Accepted Answer

They diffuse through the cell membrane, bind to intracellular receptors, and activate gene expression.

Question 4

A new virus is discovered that infects only a specific species of bacteria. What is the most likely explanation for this host specificity?

Accepted Answer

The virus recognizes and binds to specific proteins or carbohydrates on the bacterial cell surface.

Question 5

Which of the following is a real-world consequence of not completing a prescribed course of antibiotics?

Accepted Answer

It increases the risk of antibiotic-resistant bacteria developing.

Question 6

Which of the following best explains why most bacteria are not harmful to humans?

Accepted Answer

Most bacteria are either beneficial or neutral, performing functions such as nutrient extraction and outcompeting harmful bacteria.

Question 7

A patient is infected with a retrovirus. Which enzyme is critical for the replication of this virus, and what is its function?

Accepted Answer

Reverse transcriptase; it converts viral RNA into DNA, which is then inserted into the host genome.

Question 8

Which of the following is a key difference between steroid and nonsteroid hormones in terms of their mechanism of action?

Accepted Answer

Steroid hormones enter the cell and bind to intracellular receptors, while nonsteroid hormones bind to receptors on the cell surface.

Question 9

A bacterial population doubles every 20 minutes. If you start with 1 bacterium, how many bacteria will there be after 2 hours under ideal conditions? Use the formula $N = N_0 	imes 2^{(t/d)}$, where $N_0$ is the initial number, $t$ is time in minutes, and $d$ is the doubling time.

Accepted Answer

$N = 1 	imes 2^{(120/20)} = 1 	imes 2^6 = 64$

Question 10

Which of the following best describes the role of bacterial enzymes in the development of gangrene?

Accepted Answer

Bacterial enzymes dissolve connections between muscle cells, then digest the cells.

Question 11

Which of the following is a function of the human microbiota?

Accepted Answer

Extracting otherwise inaccessible calories and nutrients from food.

Question 12

Why are bacteriophages considered for use as medicine to treat bacterial infections?

Accepted Answer

They specifically infect and kill bacteria without harming human cells.

Question 13

Which of the following best explains why viruses are not classified as living organisms?

Accepted Answer

They cannot carry out metabolism or reproduce independently outside a host cell.

Question 14

Which of the following is a direct result of adding a phosphate group to a protein during cell signaling?

Accepted Answer

The protein may become activated or inactivated, altering its function.

Question 15

Which of the following is a reason why antibiotic resistance is a growing concern in hospitals?

Accepted Answer

Antibiotic-resistant bacteria, such as MRSA, are commonly acquired in hospitals and are difficult to treat.

Question 16

Which of the following best describes the genetic diversity in bacteria despite their asexual reproduction?

Accepted Answer

Bacteria can exchange plasmids, take up DNA from the environment, and acquire viral DNA, increasing genetic diversity.

Question 17

Which of the following is a correct statement about hormone target cells?

Accepted Answer

A hormone only affects cells that have the specific receptor for that hormone.

Question 18

Which of the following is a correct example of a nonsteroid hormone and its mechanism of action?

Accepted Answer

Insulin binds to receptors on the cell surface and initiates a signaling cascade inside the cell.

Viruses, Bacteria, and Cell Signaling: Study Notes for General Biology

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