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AP Biology — Unit 4 — Cell Communication — Drill 14

Drill 14 ·

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About This Drill

AP Biology — Unit 4 — Cell Communication — Drill 14 is a practice drill. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.

Practice signal transduction and feedback mechanisms with this AP Biology drill. You will identify the roles of components in an insulin signaling pathway, distinguish positive from negative feedback using a biological scenario, predict the consequences of a receptor mutation on cellular glucose uptake, interpret blood glucose data in terms of the insulin signaling cascade, and connect signal transduction to gene expression regulation.

Passage

Insulin is a peptide hormone released by beta cells of the pancreas in response to elevated blood glucose concentration. Insulin cannot cross the plasma membrane of target cells. Instead, it binds to a receptor tyrosine kinase (RTK) on the outer surface of the plasma membrane of muscle and adipose cells. Binding of insulin causes the RTK to phosphorylate itself and downstream target proteins in a phosphorylation cascade. One key outcome of this cascade is the translocation of glucose transporter proteins (GLUT4) from intracellular vesicles to the plasma membrane, allowing glucose to enter the cell. Increased glucose uptake by muscle and adipose cells reduces blood glucose concentration. When blood glucose returns to the normal range, insulin secretion from beta cells decreases. Additionally, researchers have found that in some cells, insulin signaling activates transcription factors that increase expression of genes involved in glucose metabolism and lipid synthesis.

Questions in This Drill

  1. Based on the passage, which of the following correctly identifies the role of insulin in the signal transduction pathway described?
  2. The passage describes that when blood glucose returns to the normal range after insulin is released, insulin secretion from beta cells decreases. Which of the following correctly identifies the type of feedback represented by this relationship and explains why?
  3. A mutation causes the insulin receptor tyrosine kinase (RTK) to be produced in a structurally altered form that cannot undergo phosphorylation when insulin binds. Which of the following best predicts the consequence of this mutation for glucose uptake in affected muscle cells?
  4. The passage notes that insulin signaling activates transcription factors that increase expression of genes involved in glucose metabolism. If the insulin signaling pathway is activated in a target cell, which of the following sequences of events best represents the complete pathway from insulin binding to increased gene expression?
  5. A researcher treats muscle cells in culture with a drug that irreversibly blocks all RTK phosphorylation activity in those cells. The cells are then exposed to a high concentration of insulin for 30 minutes, followed by normal insulin concentration for 60 more minutes. Which of the following best predicts the effect on glucose uptake in the treated muscle cells over this entire 90-minute period?