Biology  by Bradford
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4.3 Signal Transduction Pathways: revision map

The subtopic in the middle and four tasks round it: label a diagram, complete a table, put a process in order and fill 9 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.

Unit 4 practice questionsThe whole Unit 4 map

Topic 4.3

Signal Transduction Pathways

AP Biology · Unit 4 Cell Communication and Cell CycleName

4.3.A, 4.3.BA G protein pathway

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  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6

4.3.A, 4.3.BSignal strength and switching off

Each activated enzyme in a cascade can activate many molecules of the next, so a few ligand molecules can produce a large response: the signal is . Pathways must also switch off, since a signal that never stops would never allow a cell to respond to a new one. A mutation in a pathway that keeps a protein active whether or not the ligand is present can lead to unregulated growth, as in some cancers; a drug that blocks one step, or a toxin like cholera toxin that locks a G protein on, changes the response of the whole cell.

Topic 4.3Signal Transduction Pathways

4.3.AA phosphorylation cascade

Number the steps in order.

  1. The second kinase phosphorylates a third.
  2. The last kinase phosphorylates a target protein, causing the response.
  3. The first kinase phosphorylates, and so activates, a second kinase.
  4. The receptor activates the first kinase in the pathway.
  5. Phosphatases remove the phosphate groups and switch the pathway off.

4.3.ASecond messengers

MessengerWhere it comes fromWhat it does
made from ATP by adenylyl cyclaseactivates protein kinase A
released from the ERactivates enzymes and triggers vesicle release
IP₃made by cleaving a membrane lipidopens channels in the ER
Word bank amplifiedCalciumcAMPenzymeG proteinligandprotein kinasereceptorsecond messenger

Answer key

Every box on the sheet with its gaps filled in, as the subtopic reads in full.

  1. LabelA G protein pathway

    1. ligand
    2. receptor
    3. G protein
    4. enzyme
    5. second messenger
    6. protein kinase

  2. OrderA phosphorylation cascade

    1. The receptor activates the first kinase in the pathway.
    2. The first kinase phosphorylates, and so activates, a second kinase.
    3. The second kinase phosphorylates a third.
    4. The last kinase phosphorylates a target protein, causing the response.
    5. Phosphatases remove the phosphate groups and switch the pathway off.

  3. TableSecond messengers

    MessengerWhere it comes fromWhat it does
    cAMPmade from ATP by adenylyl cyclaseactivates protein kinase A
    Calciumreleased from the ERactivates enzymes and triggers vesicle release
    IP₃made by cleaving a membrane lipidopens channels in the ER

  4. GapsSignal strength and switching off

    Each activated enzyme in a cascade can activate many molecules of the next, so a few ligand molecules can produce a large response: the signal is amplified. Pathways must also switch off, since a signal that never stops would never allow a cell to respond to a new one. A mutation in a pathway that keeps a protein active whether or not the ligand is present can lead to unregulated growth, as in some cancers; a drug that blocks one step, or a toxin like cholera toxin that locks a G protein on, changes the response of the whole cell.