Which situations involve a cell using endocytosis?
1. a cell wraps a portion of its membrane around a droplet of nutrient‑rich water and brings the droplet inside the cell.
2. water moves across a cell membrane and into a cell through specialized protein tunnels in response to a concentration gradient.
3. digestive enzymes are disgorged into the small intestine through the cell membrane of the cell in which they were produced.
4. a free‑living single‑celled organism engulfs a smaller single celled organism and uses the smaller organism as a food source.
5. ldl cholesterol attaches to cell membrane proteins, triggering the membrane to fold around the cholesterol and bring it into the cell.