Assume that Na+ is being transported across a membrane via facilitated diffusion. Which of the following conditions would allow for the most transport of Na+ across that membrane.
Answers:
1) a gradient of less than 5% difference between sides for the Na+ and Na+ diffusing toward K+
2) a gradient of less than 5% difference between sides for the Na+ and Na+ diffusing toward Cl−
3)a gradient of more than 50% difference between sides for the Na+ and Na+ diffusing toward Cl−
4) a gradient of more than 50% difference between sides for the Na+ and Na+ diffusing toward K+
4) a gradient of more than 50% difference between sides for the Na+ and Na+ diffusing toward K+
To determine which condition would allow for the most transport of Na+ across the membrane via facilitated diffusion, we need to understand the concept of facilitated diffusion and the role of gradients.
Facilitated diffusion is a type of passive transport where molecules move across a membrane with the help of specific protein channels or carriers. These channels or carriers facilitate the movement of molecules down their concentration gradient, which means they move from an area of higher concentration to an area of lower concentration.
In this case, we are considering the transport of Na+ across a membrane. For facilitated diffusion to be maximized, there should be a significant concentration gradient of Na+ across the membrane.
Let's evaluate each answer choice:
1) a gradient of less than 5% difference between sides for the Na+ and Na+ diffusing toward K+:
This condition suggests a very small concentration gradient (less than 5%) between the two sides of the membrane. In this scenario, there would not be a significant driving force for Na+ to move across the membrane via facilitated diffusion. Therefore, this condition would not allow for the most transport of Na+.
2) a gradient of less than 5% difference between sides for the Na+ and Na+ diffusing toward Cl−:
Similar to the first option, this condition also suggests a minimal concentration gradient between the two sides of the membrane. As a result, the driving force for Na+ to move across the membrane via facilitated diffusion would be weak. Thus, this condition would not allow for the most transport of Na+.
3) a gradient of more than 50% difference between sides for the Na+ and Na+ diffusing toward Cl−:
This condition suggests a large concentration gradient (more than 50%) between the two sides of the membrane. The difference in concentrations creates a significant driving force for Na+ to move across the membrane via facilitated diffusion. Therefore, this condition would allow for the most transport of Na+.
4) a gradient of more than 50% difference between sides for the Na+ and Na+ diffusing toward K+:
This condition is similar to the third option, suggesting a substantial concentration gradient that enables Na+ to move across the membrane via facilitated diffusion efficiently. Therefore, this condition would also allow for the most transport of Na+.
In conclusion, the conditions that would allow for the most transport of Na+ across the membrane via facilitated diffusion are options 3) and 4), which involve a gradient of more than 50% difference between sides for the Na+ and Na+ diffusing toward Cl− or K+.
The correct answer is:
4) a gradient of more than 50% difference between sides for the Na+ and Na+ diffusing toward K+.