Sodium and potassium ions can easily diffuse through the lipid bilayer of plasma membranes.
Answer the following statement true (T) or false (F)
False
Clarify Question
What is the key concept addressed by the question?
• This question is asking you to recall the solubility of ions in either lipids or water to determine why ions do not easily diffuse through plasma membranes.
What type of thinking is required?
• Analyze level:
o This is an analyze question because you have to break the solubility of ions into two categories, water solubility and lipid solubility, to understand how the different solubility levels explain poor diffusion of ions across plasma membranes.
Gather Content
What do you already know about the solubility of ions in water? What other information is related to the question?
• To answer this question you need to remember that ions have a high solubility in water and a low solubility in lipids.
• Additionally, to answer this question you should recall that ions do not readily diffuse across plasma membranes.
Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
• At this point you should have everything you need to answer the question. Remember that the solubility of ions in water is high and the solubility of ions in lipids is low. Note that this relationship explains why ions do not readily diffuse across plasma membranes.
• Because the question asks what would need to change to allow ions to readily diffuse across plasma membranes you should look for an answer that flip flops the rule stated above (the solubility of ions in water is high and the solubility of ions in lipids is low). Therefore, the best answer is the low solubility in lipids would need to increase and the high solubility they have in water would have to decrease.
• The three answers that describe changes in solubility only consider one side of the equation, either changing the lipid or water solubility. However, effects on ion movement require interactions with both water and lipids so both must be considered. Therefore these responses are incorrect. The remaining answer indicates ion size is a factor, this is not accurate.
Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
• Analyze level:
o Answering this question correctly depended not only on distinguishing between the solubility of ions in water and in lipids, but on your ability to break down, or analyze, the impact of changes in ion solubility for ion diffusion. If you got an incorrect answer, did you remember that ions are readily soluble in water, or that ions are not readily soluble in lipids? Did you have trouble breaking down the role of ion solubility to determine the correct answer?
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