Signal Transduction Pathways Answers

Signal Transduction Pathways What happens inside of a cell when a signal has been received? Why? When cells release signal molecules (ligands) to send a message, and the message is received, a whole host of events take place inside the cell. The ultimate goal is a response-a gene is turned on, a protein is manufactured, an enzyme is activated, the cell divides or dies, etc. There are many responses that could occur, but the pathways to those responses are very similar. Model 1 - Basic Signal Transduction Pathway Ligand 2 T Receptor protein Cell membrane Cytoplasm Activated relay protein 1 Activated relay protein 2 Activated relay protein 2 Activated relay protein 2 Response Response < Response 1. According to Model 1, does the signal transduction pathway occur inside or outside of a cell? INSDE 2. Compare the shape of the ligand in Model 1 to the shape of the receptor protein. thy fit boyether exucty 3. The four steps in the signal transduction pathway are listed below. Label the diagram above with the Roman numerals to indicate where on the diagram each step is taking place. I. Signaling ΙΙ. Reception III. Transduction IV. Response Signal Transduction Pathways 1 STOP 4. 5. Based on the diagram in Model 1 and your labels, propose a definition for "transduction" in the context of the signal transduction pathway. A "Fronslation" of the th siynal into tHhe response Amplification often occurs during the transduction step in the signal transduction pathway. a. Define amplification" as it is used in everyday language. Maling sometting Coudes or mure pomerfid b. Explain how the signal in Model 1 was amplified. One ligind lends to a Mrecfoled resporse 6. List several possible responses that could occur due to a signal being received by a cell. (Hint: There are several listed in the Why? ymab- box.) - eneyme actintin denth -Geneacfiration -protein Mamulacture 7. Once the response is achieved in a cell, what would need to occur to stop the response? The relay proteins would reed to be deactiwatd Cat base, tHhe lgond wall nend to demple m reeeptor? Read This! Signal transduction pathways are as varied as the species on Earth, but each of them follow the same basic steps. Reception may occur by the ligand attaching to a receptor protein or the ligand may travel through the cell membrane by diffusion. Transduction may occur by one protein or by several proteins activating each other in a cascade. Keep this in mind as you continue working through this activity. 2 POGIL™ Activities for AP* Biology Model 2 - Phosphorylation Cascade Nonamplification step Amplification step 1 Inactive relay protein Cell membrane 2 Active Pre kinase 2 Cytoplasm Active rela Inac protei kina Inactive ase 2 cinaśe Active protein kinase Nucleus XXXXXXXXXXXXX protein Active 3 protei kinase ine 1 ATP Acive 4 Active protein protein protein kinase 3 ADP kinase 2 1 Inactive Inactive ATP protein 5 1 kinase 2 kinase 3 ADP APP Inactive protein CATPY Active transcription tacto 7 Ac proter kinase 3 ATP ADP ADP PATP 8. Refer to Model 2. Describe the event that sets off a phosphorylation cascade inside ofa cell. The ligird cowses an reeeptor proten to catimte a reby 9. protein. Phosphorylation is a process that adds a phosphate group onto a protein to "activate" it-that is, to change its shape enough that it can function properly. a. b. Which step(s) in the phosphorylation cascade illustrated in Model 2 include phosphorylation? 457 Where do the phosphate groups come from that are added to the proteins during phosphorylation? ATP 10. According to Model 2, what class of enzymes performs phosphorylation? Protein k mases 11. Identify the steps in Model 2 that represent reception, transduction, and response for the phosphorylation pathway. Reception Transduction 2-6 Signal Transduction Pathways Response 3 4 STOP 12. What is the cell's response to the signal received in Model 2? ere A louc pon foanr actnts.(mn somsphot agigin) 13. In Model 2, steps 3, 4, and 5 are shown as amplification steps. Describe what that means in terms of this signal transduction pathway example. more mderines than the origiml ligerd awe becoing ,noohued. 14. What advantage would there be to an organism if the signal transduction pathway had several amplification steps? 15. A single Cor low count of) ligired molkadels) com lard to u magnifud response by te cell. Describe what would occur in the cell if the activated protein kinase enzymes continued to be active for a long period of time. ATP modecuks would bccome veed yp 16. 17. What would need to occur in the cell to deactivate the protein kinase enzymes? Dephospharghiton ird deactiontiuin ofthe relay prakin Protein phosphatases are enzymes that remove phosphate groups from proteins. Complete the illustration in Model 2 by adding at least two protein phosphatases (PP) to show how the cell is returned to inactive status. 18. Although signal transduction pathways vary among species, there are several common elements. Explain how a biologist might use details about signal transduction pathways used in different species as evidence for evolutionary relatedness. Speeires with common sigal parthanys ortmore closely relted thanthese with clesirilen pathway, Siynal pathways appar to be ancient. POGIL™ Activities for AP* Biology Extension Questions Model 3 - Secondary Messengers Cell membrane Cytoplasm Active relay protein 2 Response 5 Active relay protein 3 Transport protein Secondary messenger 19. Consider the signal transduction pathway in Model 3. What event begins the process of producing a cellular response? Alyird binds to a receptor prokin 20. Locate the secondary messenger molecules in Model 3. a. Describe the type of diffusion that is used to get the secondary messengers into the cell. Facititated diffusion b. What activates or opens the transport protein channel that allows the secondary messengers to enter the cell? An active rely protein Signal Transduction Pathways 5 9 Read This! Relay molecules and secondary messengers have essentially the same jobs in signal transduction pathways. However, relay molecules are almost always proteins that require activation. They are large and do not diffuse through the cell quickly. Secondary messengers on the other hand are small, water soluble molecules that can diffuse quickly. They may or may not need activation before they are able to move the signal on to the next step in the process. Cyclic AMP (cAMP) and calcium ions (Ca2+) are common secondary messengers in human systems. 21. Within an organism it is critical that signals between cells are very specific. For example, if ligand A is meant to activate immune system cells to reproduce in response to an infection, it should not also cause other cells to grow as if they had received a growth hormone. When a ligand is released, what prevents all of the cells in the body from being affected? A cell needs speerfic Nereptor molecules,to be affedted by a releasad ligand