AP BIOLOGY

Detailed explanation-1: -Around 99 percent of filtrate formed is reabsorbed. The epithelial cells of renal tubule reabsorb these substances either by active or passive mechanisms. Substances like glucose, amino acids, Na+, are reabsorbed by active transport.

Detailed explanation-2: -Glucose is reabsorbed by active transport and PAH is secreted by active transport. Active transport is an enzyme dependent process. (transporters are enzymes). All enzyme-mediated processes are saturable.

Detailed explanation-3: -Glomerular filtration is a passive process as cellular energy is not used at the filtration membrane to produce filtrate.

Detailed explanation-4: -Solution : Gloucose is taken back from glomerular filtrate through active transport in proximal convoluted tubule.

Detailed explanation-5: -Under normal circumstances, up to 180 g/day of glucose is filtered by the renal glomerulus and virtually all of it is subsequently reabsorbed in the proximal convoluted tubule. This reabsorption is effected by two sodium-dependent glucose cotransporter (SGLT) proteins.