We would be unable to absorb sufficient nutrients from food.
| Feature | Active Transport | Diffusion | Osmosis | | :--- | :--- | :--- | :--- | | | Low → High Concentration | High → Low Concentration | High → Low Water Potential | | Energy (ATP) | Required | Not Required | Not Required | | Proteins Needed | Yes (Carrier Proteins) | Sometimes (Channel Proteins) | No (Aquaporins aid but don't use energy) | | Selectivity | Highly Selective | Selective (based on size/charge) | Specific to water | active transport in humans