Question at position 1 Which of the following substances moves easily through the cell membrane?Potassium ionsGasesSodium ionsGlucoseAmino acids单项选择题
A
Potassium ions
B
Gases
C
Sodium ions
D
Glucose
E
Amino acids

Question

Question at position 1 Which of the following substances moves easily through the cell membrane?Potassium ionsGasesSodium ionsGlucoseAmino acids

BlackTom AI · Accepted Answer

Consider the question about which substance moves easily through the cell membrane. 
Option 1: Potassium ions — potassium is a charged ion and cannot freely cross the lipid bilayer without a channel or transporter; their movement is tightly regulated by membrane proteins, not spontaneous diffusion. 
Option 2: Gases — many small nonpolar or lightly polar gases (such as O2 and CO2) diffuse readily across the phospholipid membrane down their concentration gradient, requiring no energy or specialized transporters. This is why gases are described as diffusing easily through membranes. 
Option 3: Sodium ions — like potassium, sodium is a charged ion; without specific channels or pumps, it cannot efficiently cross the membrane, so this option is incorrect for “moves easily.” 
Option 4: Glucose — glucose is a relatively large, polar molecule; it requires membrane transport proteins (GLUT transporters) to cross, so it does not move easily by simple diffusion. 
Option 5: Amino acids — most amino acids are polar or charged at physiological pH; they rely on transporters or facilitated diffusion and do not pass through the lipid bilayer with ease on their own. 
In summary, the key idea is that small, nonpolar gas molecules diffuse fastest through the membrane, whereas ions and larger polar molecules depend on channels or transporters; thus gases can move easily, while the other options require specific mechanisms or are impeded by charge or size.

Question at position 1 Which of the following substances moves easily through the cell membrane?Potassium ionsGasesSodium ionsGlucoseAmino acids单项选择题

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