How does each of the following molecule pass through the plasma membrane in the described scenarios?
a. both simple diffusion and facilitated diffusion
b. facilitated diffusion
c. active transport
d. simple diffusion
selectabcd 1.
molecular oxygen (o2) and carbon dioxide (co2) traveling down their concentration gradient.
selectabcd 2.
inorganic ions traveling down their concentration gradient
selectabcd 3.
glucose traveling against its concentration gradient
selectabcd 4.
water molecules (h2o) traveling down their concentration gradient

1. simple diffusion.

2. facilitated diffusion.

3. active transport.

4. both simple and facilitated diffusion.

Explanation:

1. Simple diffusion can be defined as transport of small, non-polar, uncharged molecules, such as urea, gases, water through the lipid bilayer without the help of transport proteins.

As molecular oxygen and carbon dioxide are gases, these molecules would be transported by simple diffusion.

Thus, statement 1 correctly matches with option (D).  

2. Facilitated diffusion involves transport of polar, charged, and large molecules, such as ions, glucose, and amino acids with the help of membrane proteins, known as transport proteins.

Passive transport is an example of of facilitated diffusion, which includes transport of molecules from higher to lower concentration (along their concentration gradient) without use of energy.  

As ions are travelling down their concentration gradient, it is an example of facilitated transport.

Thus, statement 2 correctly matches with option (B).  

3. Active transport is a type of facilitated diffusion that involves transport of molecules against their concentration (from lower to higher) with the help of energy. As glucose is travelling against its concentration, it is an example of active transport.  

Thus, statement 3 correctly matches with option (C).  

4. Water molecules are small, charged molecules that can be transported by both simple diffusion through lipid bilayer or facilitated diffusion through transport proteins, aquaporins.

Thus, statement 4 correctly matches with option (A).  

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