Question

traveling molecules
for the following scenarios, determine whether the molecules in the scenario are moving by (s) simple diffusion, (f) facilitated diffusion, or (a) active transport.

1. f for water to travel across the cell membrane at a substantial rate, the water molecules travel through protein channels known as aquaporins.
2. while water molecules are polar, they are also very small. one fact not mentioned in the video is that some water molecules are able to squeeze directly through the phospholipid bilayer due to their small size.
3. charged ions are traveling through a cell membrane with the concentration gradient.
4. cells lining the gut need to take in glucose, but at a certain time, the concentration of extracellular glucose is lower than the concentration already stored in the cells.
5. at a certain time, glucose is in a high concentration outside of a cell and needs to travel through the membrane into the cell.

Explanation:

Step1: Analyze question 9

Water molecules squeezing through phospholipid bilayer (no protein channels, small non - polar like movement).

Step2: Analyze question 10

Charged ions moving with concentration gradient (no energy, but need channels as ions are charged).

Step3: Analyze question 11

Glucose moving against concentration gradient (needs energy).

Step4: Analyze question 12

Glucose moving with concentration gradient (no energy, but may need channels as glucose is polar).

Answer:

1. S
2. F
3. A
4. F