Read the passage below and answer the questions that follow.
In historical studies, researchers investigated the control of glucose by treating healthy rabbits with alloxan, a chemical that selectively destroys β\betaβ-cells in the pancreatic islets. These rabbits quickly exhibited symptoms resembling Type 1 diabetes, producing vast amounts of urine with a high glucose concentration. This was because their blood glucose levels rose far above the normal renal threshold of 8.5 mmol/dm3, leading to glucose being excreted in the urine.
In another experimental group, researchers surgically ligated the pancreatic duct of healthy rabbits to block the flow of pancreatic juice into the duodenum. Although the exocrine acinar tissue of these rabbits underwent atrophy (degeneration), the animals maintained normal blood glucose levels and did not develop glycosuria (glucose in urine).
Subsequently, researchers prepared an aqueous extract from the pancreatic tissue of healthy donor rabbits using a cold, buffered saline solution. When this extract was administered intravenously to the diabetic rabbits, their plasma glucose levels returned to normal.
We now understand that blood glucose homeostasis is maintained by the opposing actions of insulin and glucagon, both produced by the Islets of Langerhans. Elevated blood glucose stimulates the β\betaβ-cells to release insulin into the bloodstream, where it travels to the liver and skeletal muscles to promote the conversion of glucose into glycogen, a highly branched, insoluble storage polysaccharide. Conversely, a drop in blood glucose prompts α\alphaα-cells to secrete glucagon, which triggers the breakdown of glycogen back into soluble glucose.
Explain what is meant by the term absorption as it occurs in the mammalian small intestine.
Explain why the rabbits treated with alloxan produced urine containing glucose.
Name two digestive enzymes produced by the pancreas that are normally secreted into the duodenum.
Suggest why the rabbits with a ligated pancreatic duct were still able to regulate their blood glucose levels.
The researchers who injected the pancreatic extract into the diabetic rabbits should have carried out a control experiment. Explain the control experiment they should have conducted.
Name the blood vessel that carries absorbed glucose directly from the ileum to the liver.
Suggest one property of glycogen that makes it an advantageous storage molecule in cells compared to glucose.
The control of blood glucose level is an example of homeostatic coordination.
Describe the stimulus when blood glucose is high.
Name the receptor that detects this stimulus.
Name an effector organ for this response.
Describe the response of this effector in lowering blood glucose levels.
