Hi @2022CSBCPSONSummerUndergraduateFellows, Today's lecture recording is posted in the [Curriculum](https://www.synapse.org/#!Synapse:syn29616137/wiki/617441) page. Here are the answers for the Module 6 questions (**NOTE:** I just realized that Jay had also shared answers to the "Thinking more" questions, so I'll amend my Module 5 post to add those.) Again, if you have questions, please post here, email the [mentors](mailto:CSBCPSONminiDREAMMentors@synapse.org), or email Jay [directly](mailto:houxx149@umn.edu). **Exercise 3: substrate is deformable** Challenge Questions: * What is the approximate frequency for clutches to unbound (unbound_freq_deform)? **Answer:** 0.076/s (0.05-0.1 will be fine) * What is the mean module force (mforce_mean_deform)? **Answer:** 76.6 pN (70-85 will be fine) Thinking more about the exercise: * What do you observe? **Answer:** We should see bound clutch number accumulates and unbound with time, so do module force and substrate deformation. * Is substrate deformation = module force * subK? (Equation_SubDeform_MForce = yes or no) **Answer:** Yes * How will subK affect simulation results? **Answer:** When subK is small, the system will have an equilibrium bound clutch number, and module force will keep increasing within a long period before it fails. When subK is large, clutches will bind and unbind very frequently, with high unbound and module force frequency * When subK becomes very large, will the results become similar to Exercise 2? **Answer:** Yes * What is the biological behavior represented by this exercise? **Answer:** The substrate stiffness can change the clutch adhesion dynamics, and further more change the protrusion dynamics, and cell migration **Exercise 4: the relation between traction force and substrate stiffness** Challenge Question: * What is the optimal stiffness for the maximum traction force? **Answer:** 1 pN/nm Thinking more about the exercise: * What do you observe? **Answer:** There is an optimal traction force at the stiffness of 1pN/nm. * Why there is the optimal stiffness for the maximum traction force? **Answer:** When the substrate is soft, it takes a longer time to accumulate traction force, and hence the mean traction is low. When the substrate is stiff, the adhesion fails frequently, and the mean traction is low. Therefore there is an optimal stiffness when the cell can accumulate the highest adhesion and traction force. * What is the biological behavior represented by this exercise? **Answer:** The cell can adhere to the tissue with the optimal stiffness. **Exercise 5: differential traction between T-47D and MD-MBA-231 line** Challenge Question: * What is the ratio between the traction force of MD-MBA-231 and T-47D cell line? **Answer:** 245/15 = ~16 (10-20 will be fine) Thinking more about the exercise: * What do you observe? **Answer:** We predicted that MD-MBA-231 cell line has higher traction force than T-47D cell line. * What is the biological behavior represented by this exercise? **Answer:** We can link the VIM expressions to the adhesion clutch component in the cell traction.