8. (F) Facilitated diffusion: For water to travel across the cell membrane at a substantial rate, the water molecules travel through protein channels known as aquaporins.
9. (S) Simple diffusion: 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.
10. (S) Simple diffusion: Charged ions are traveling through a cell membrane with the concentration gradient.
11. (A) Active transport: 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.
12.(F) Facilitated diffusion: At a certain time, glucose is in a high concentration outside of a cell and needs to travel through the membrane into the cell.
The above choices are made based on the basic definitions of active transport, facilitated diffusion and simple diffusion.
Active transport: The movement of the ions or molecules to a region having higher concentration across the membrane requiring the help of energy or enzymes is active transport.
Facilitated diffusion: This type of transport involves passive movement of the molecules or is a type of passive transport where the movement of the molecules takes place from higher to lower concentration region occurs with the aid of a carrier molecule such as a transport or carrier protein.
Simple diffusion: This process involves movement of ions or molecules from high concentration region to low concentration region through a semipermeable membrane.
