a) Generally speaking, the ability of a substance to move across a membrane by passive diffusion is enhanced by decreasing size and by an increasing octanol/water coefficient. T or F
To determine if the statement is true or false, we need to understand the concepts mentioned in the statement - passive diffusion, size, and octanol/water coefficient.
1. Passive diffusion: This refers to the movement of substances across a membrane without the use of energy. It occurs from an area of high concentration to low concentration, thereby achieving equilibrium.
2. Size: In general, smaller molecules can move more easily across a membrane via passive diffusion. This is because they can pass through the pores or channels in the membrane more readily compared to larger molecules.
3. Octanol/water coefficient: This is a measure of a substance's ability to dissolve in octanol (a lipid-soluble substance) compared to its ability to dissolve in water (a polar substance). A higher octanol/water coefficient indicates that the substance is more lipid-soluble and can cross the cell membrane more easily.
Now, let's evaluate the statement:
"The ability of a substance to move across a membrane by passive diffusion is enhanced by decreasing size and by an increasing octanol/water coefficient."
Given what we know, the statement is true. Decreasing the size of a substance allows it to pass through the membrane more easily, and a high octanol/water coefficient indicates greater lipid solubility, making it easier for the substance to cross the lipid bilayer of the cell membrane.
So, the answer is: True.