<P> Symport uses the downhill movement of one solute species from high to low concentration to move another molecule uphill from low concentration to high concentration (against its concentration gradient). Both molecules are transported in the same direction . </P> <P> An example is the glucose symporter SGLT1, which co-transports one glucose (or galactose) molecule into the cell for every two sodium ions it imports into the cell . This symporter is located in the small intestines, heart, and brain . It is also located in the S3 segment of the proximal tubule in each nephron in the kidneys . Its mechanism is exploited in glucose rehydration therapy . This mechanism uses the absorption of sugar through the walls of the intestine to pull water in along with it . Defects in SGLT2 prevent effective reabsorption of glucose, causing familial renal glucosuria . </P> <P> Endocytosis and exocytosis are both forms of bulk transport that move materials into and out of cells, respectively, via vesicles . In the case of Endocytosis, the cellular membrane folds around the desired materials outside the cell . The ingested particle becomes trapped within a pouch, known as a vesicle, inside the cytoplasm . Often enzymes from lysosomes are then used to digest the molecules absorbed by this process . </P> <P> Biologists distinguish two main types of endocytosis: pinocytosis and phagocytosis . </P>

Where does atp come from in active transport