Which one of the following molecules can MOST easily pass through the plasma membrane unassisted?
A. Ca2+, a positive ion
B. Cl−, a negative ion
C. CO2, a nonpolar gas
D. glucose, a large sugar
The smaller and nonpolar molecules pass through more easily. So pick CO2.
Well, let's think about this in a humorous way, shall we?
A. Ca2+, a positive ion: Sorry, Ca2+ is like that overly positive person who just can't seem to squeeze through small spaces. It's a bit too big and charged to pass through the membrane unassisted.
B. Cl−, a negative ion: Oh, Cl−, you're like the negative Nancy of ions. Negativity doesn't get you very far in this case. The charge makes it difficult for you to pass through the membrane.
C. CO2, a nonpolar gas: CO2, my gassy friend! You're small, nonpolar, and nimble. Like a sneaky ninja, you can easily slip through the plasma membrane without much trouble. You da real MVP!
D. Glucose, a large sugar: Now, glucose, you're the sweetest molecule. Unfortunately, your size is a real challenge. It's like trying to fit a hippo through a keyhole – not gonna happen without some serious assistance.
So, the winner here is good ol' CO2, the nonpolar gas who breezes through the membrane like a stealthy ninja.
The molecule that can most easily pass through the plasma membrane unassisted is the one that is nonpolar and small in size. Among the options given, CO2 (carbon dioxide), a nonpolar gas, fits this description best. Therefore, the correct answer is C. CO2.
To determine which molecule can most easily pass through the plasma membrane unassisted, we need to understand the properties of the plasma membrane and the molecules in question.
The plasma membrane is composed of a phospholipid bilayer, which consists of two layers of phospholipids. Phospholipids have a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. This arrangement results in the formation of a selectively permeable barrier, allowing certain substances to pass through while impeding the movement of others.
Now, let's evaluate each molecule:
A. Ca2+, a positive ion: Since the plasma membrane is hydrophobic, ions that are charged (positive or negative) have difficulty crossing it unassisted. Thus, Ca2+ would have difficulty passing through the plasma membrane.
B. Cl−, a negative ion: Similar to Ca2+, Cl− is charged and would have difficulty crossing the plasma membrane unassisted.
C. CO2, a nonpolar gas: CO2 is a nonpolar molecule, meaning it does not have a charge and is not attracted to the hydrophobic interior of the membrane. Nonpolar molecules can diffuse easily through the lipid bilayer, so CO2 can pass through the plasma membrane unassisted.
D. Glucose, a large sugar: Unlike CO2, glucose is a polar and relatively large molecule. Polar molecules do not easily pass through the hydrophobic core of the plasma membrane, and the size of glucose further hinders its unassisted movement across the membrane.
Based on this analysis, the molecule that can most easily pass through the plasma membrane unassisted is C. CO2, a nonpolar gas.