Cell Communications and Cell Cycle PDF

Unit 4: Cell Communications and Cell Cycle Topic 4.4 Changes in Signal Transduction Pathways IST-3: Cells communicate by generating, transmitting, receiving, and responding to chemical signals. Changes in Signal Transduction Pathways Di...

Unit 4: Cell Communications and Cell Cycle Topic 4.4 Changes in Signal Transduction Pathways IST-3: Cells communicate by generating, transmitting, receiving, and responding to chemical signals. Changes in Signal Transduction Pathways Different kinds of cells have different collections of proteins These different proteins (enzymes) allow cells to detect and respond to different signals Even the same signal can have different effects in cells with different proteins and pathways  Changes in Signal Transduction Pathway Same ligand can have different effect on different types of cells. Ex: Metformin is a common drug that treats type II diabetes, works on liver and skeletal muscle. It can also increase tissue sensitivity to insulin. AMPK is an enzyme AMP kinase. Reduce glucose production by the liver Improve insulin sensitivity to take in glucose from the blood Decrease glucose absorption from the intestines The role of insulin in glucose uptake Example of Signal Transduction Example: glucose regulation with insulin In the presence of glucose, GLUT4 vesicle fuses with cell membrane GLUT4 allows the glucose to enter the cell Changes in Signal Transduction Pathways Mutations in any domain of the receptor protein or in any component of the signaling pathway may affect the downstream components by altering the subsequent transduction of the signal.  Changes in Signal Transduction Pathways Changes in signal transduction pathways can alter cellular responses Chemicals that interfere with any component of the signaling pathway may activate or inhibit the pathway  Changes in signal transduction pathways can alter cellular responses Chemicals that interfere with any component of the signaling pathway may activate or inhibit the pathway How Cholera bacteria make people sick 4.5 Feedback Organisms use feedback mechanisms to maintain their internal environments and respond to internal and external environmental changes. Negative feedback: maintain homeostasis Positive feedback: amplifying responses and processes Negative Feedback Negative feedback mechanisms maintain homeostasis for a particular condition by regulating physiological processes. If a system is perturbed, negative feedback mechanisms return the system back to its target set point. These processes operate at the molecular and cellular levels. Maintains homeostasis at a set point or range.​ The response (or feedback) to the stimulus decreases the occurrence of the stimulus or is opposite of the stimulus.  Synthetic hormone Using synthetic hormone for a long period of time can disrupt natural production of the hormone. Examples: Prednisone is like cortisol, a hormone naturally made by your adrenal glands. If you take prednisone for more than a few weeks, your adrenal glands decrease cortisol production. A gradual reduction in prednisone dosage gives your adrenal glands time to resume their usual function.  Positive Feedback Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set point. Amplification occurs when the stimulus is further activated, which, in turn, initiates an additional response that produces system change. Amplifying in nature. Examples: The response is to amplify or increase Blood clotting the occurrence of the stimulus. Childbirth Lactation (milk production) Fruit ripening Positive Feedback Blood Clotting