1. The hormone insulin is released from the pancreas in response to increased levels of glucose in the blood. If blood glucose levels are controlled by negative feedback, what effect would insulin have on blood glucose levels? The pancreas secretes insulin and glucagon. Both hormones work in balance to play a vital role in regulating blood sugar levels. If the level of one hormone is higher or lower than the ideal range, blood sugar levels may spike or drop. 2. Transport by a hepatocyte (liver cell) Liver cells are packed with glucose. If the concentration of glucose in a liver cell is higher than in the surrounding fluid, what mechanism could the cell use to import even more glucose? Why would only this mode of transport work? Active transport would be used to transport glucose into a liver cell. Only this mode of transport would work because it is the only mechanism that moves "uphill" against the concentration gradient. 3. Transport between nephron and bloodstream In the kidneys, water moves by osmosis from tubules called nephrons to the bloodstream. Do you expect a nephron to be hypotonic, isotonic, or hypertonic relative to the blood? Explain.