The cell membrane for it controls what materials should enter in and out of the cell
The cholecystokinin generates a satiety or nausea sensation to the brain, quenching the appetite once it has eaten enough, occurs naturally in the human organism in the small intestine, secreted from the cells of the duodenum and jejunum to promotes fats absorption in the digestion process.
All that is slow gastric emptying.
All elements of a ecosystem work together, the sun provides sun light which plants use photosynthesis for food. Small animals eat the producers aka the plants. Then other animals eat those. And so on if a plant wasn't alive then the whole ecosystem will fail.
