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In a hypertonic solution, water flows through aquaporins embedded in the plasma membrane of the cell. This type of transport is best known as which of the following?

  • A. active transport
  • B. diffusion
  • C. osmosis
  • D. facilitated diffusion
Correct Answer: C

Rationale: In a hypertonic solution, water moves out of the cell through aquaporins due to the higher solute concentration outside the cell. This process is known as osmosis, which involves the movement of water across a selectively permeable membrane from an area of low solute concentration to an area of high solute concentration. Osmosis is a passive process, meaning it does not require energy input. Active transport, on the other hand, requires energy to move substances across a membrane. Diffusion is the movement of molecules from an area of high concentration to low concentration without the involvement of aquaporins. Facilitated diffusion, while also passive, requires specific carrier proteins for transport but does not involve the movement of water as seen in osmosis.

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Through which of the following transport mechanisms do water molecules enter cells?

  • A. Facilitated diffusion
  • B. Electrochemical gradients
  • C. Gated channels
  • D. Proton pumps
Correct Answer: A

Rationale: Water molecules enter cells through facilitated diffusion. Facilitated diffusion is the passive movement of molecules across a cell membrane with the help of specific transport proteins. In the case of water, it moves through specialized channels called aquaporins using this mechanism, allowing it to cross the membrane more efficiently than by simple diffusion. While electrochemical gradients, gated channels, and proton pumps play roles in transporting other substances and ions, they are not directly involved in the transport of water molecules into cells.

A researcher wants to gather data on the average wing strength of all birds found in the American Northwest. The researcher only has one small net, so all large birds were excluded from the study. The researcher's results were different than expected, but he believes his data includes enough birds to estimate the strength of all birds.

Why should data be rejected in this scenario?

  • A. Data contradicts the control group.
  • B. Data were different from expectations.
  • C. Data cannot be displayed graphically.
  • D. Data are based on flawed methodology.
Correct Answer: D

Rationale: The correct answer is D because when data are based on flawed methodology, it means that the way the data were collected, analyzed, or interpreted was not done correctly. This can lead to unreliable results that do not accurately represent the population being studied. In this case, if the researcher's methodology was flawed, it would be a valid reason to reject the data as it would not provide a valid estimate of the average wing strength of all birds found in the American Northwest.

Which of the following immune system molecules creates pores in the cell membrane of their target cells to destroy the cell?

  • A. Lymphotoxins
  • B. Perforins
  • C. Interferons
  • D. Cytokines
Correct Answer: B

Rationale: Perforins are immune system molecules that function by creating pores in the cell membrane of target cells. These pores compromise the cell's integrity, ultimately leading to cell destruction. Lymphotoxins induce cell death, but they do not create pores in the cell membrane like perforins. Interferons are signaling proteins that regulate the immune response, while cytokines are a diverse group of proteins involved in cell signaling during immune reactions. Perforins specifically target cell membranes, disrupting their integrity and leading to cell destruction, making them the correct answer in this context.

What is a common cause of a tsunami?

  • A. Earthquakes
  • B. Sunspot activity
  • C. Lightning strikes
  • D. Flooding
Correct Answer: A

Rationale: Earthquakes are a common cause of tsunamis. When an earthquake occurs under the ocean, it can displace a large volume of water, triggering a series of powerful waves known as a tsunami. Sunspot activity, lightning strikes, and flooding do not directly cause tsunamis. Therefore, the correct answer is earthquakes, as they are the primary geological event that leads to the formation of tsunamis.

Which of the following respiratory structures is affected by a disease that disrupts gas exchange, such as emphysema?

  • A. Trachea
  • B. Alveoli
  • C. Secondary bronchi
  • D. Primary bronchi
Correct Answer: B

Rationale: Emphysema is a condition that primarily affects the alveoli in the lungs. Alveoli are tiny air sacs where the exchange of oxygen and carbon dioxide occurs. In emphysema, the walls of these air sacs break down, reducing the surface area available for gas exchange. This leads to impaired respiratory function, making it harder for oxygen to enter the bloodstream and for carbon dioxide to be removed. Therefore, the correct answer is the alveoli (Choice B).

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