Unit 4 Review

1. Unit 4 Review

2. Explain what happens in the signaling pathway between yeast mating cells.

3. Explain what happens in the signaling pathway between yeast mating cells. • Exchange of mating factors • A cell secretes an a mating factor, which binds to receptors on the alpha cell • Alpha cell secretes an alpha mating factor, which binds to receptors on the a cell • Mating • The two mating factors cause the cells to grow towards each other and result in fusion • New a/alpha cell • Fused cell includes all the genes from the original cell

4. What are the two types of local signaling? Explain how they work. • What is the type of long-distance signaling? Explain how it works.

5. What are the two types of local signaling? Explain how they work. • Paracrine signaling: secreting cell acts on nearby target cell by discharging molecules of a local regulator • Synaptic signaling: nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell • What is the type of long-distance signaling? Explain how it works. • Hormone signaling: specialized endocrine cells secrete hormones into body fluids; travel all over the body but only affect specialized target cells

6. Match the words below with their definition. _____Hormones _____Ligand _____Local Regulators _____Signal transduction pathway _____Transcription factor • A molecule that specifically binds to another molecule • Circulating chemical signal that act on specific target cells to change their function • Control which genes are turn on 4. Messenger molecules that influence cells nearby 5. The process by which a signal on a cell’s surface is converted into a specific cellular response

7. Match the words below with their definition. __2__Hormones __1__Ligand __4__Local Regulators __5__Signal transduction pathway __3__Transcription factor • A molecule that specifically binds to another molecule • Circulating chemical signal that act on specific target cells to change their function • Control which genes are turn on 4. Messenger molecules that influence cells nearby 5. The process by which a signal on a cell’s surface is converted into a specific cellular response

8. What do signal molecules have to be in order to reach an intracellular receptor? • What happens to an intracellular receptor after a signal molecule has bonded to it?

9. What do signal molecules have to be in order to reach an intracellular receptor? • Small • Hydrophobic • What happens to an intracellular receptor after a signal molecule has bonded to it? • It enters the nucleus and turns on specific genes • Bound protein stimulates the transcription of the genes into mRNA • mRNA moves to the cytoplasm and is translated into a specific protein by the ribosomes

10. Explain how a G-protein-linked receptor works. • Explain how a receptor tyrosine kinase works.

11. Explain how a G-protein-linked receptor works. • Signal molecule binds to receptor protein, which causes receptor protein to change shape • Attaches to G protein • GDP replaced by GTP, which activate the G protein • Activated G protein binds to an activated enzyme • G protein hydrolyzes the GTP to GDP, which deactivates the protein

12. Explain how a receptor tyrosine kinase works. • Signal molecule binds to receptor protein • Two polypeptides come together to form a dimer • Dimerization activates tyrosine-kinase region of polypeptide • Tyrosine kinase adds a phosphate from ATP • Relay proteins bind to the each tyrosine, which activates the proteins • Each activated protein triggers a transduction pathway

13. Explain how an ion-channel receptor works. • Briefly explain what two things Sutherland discovered from his experiment with epinephrine.

14. Explain how an ion-channel receptor works. • Ligand binds to receptor • Ion gate opens • Specific ions flow through the open channel • Ligand then dissociates • Closes the ion gate • Briefly explain what two things Sutherland discovered from his experiment with epinephrine. • Epinephrine does in directly interact with the enzyme • Plasma membrane is involved in transmitting the epinephrine signal

15. Match the signaling molecule to the appropriate pathway: _____Neurotransmitter _____Growth factor _____Hormones _____Yeast mating factors • Receptor tyrosine kinase • G-protein-linked receptor

16. Match the signaling molecule to the appropriate pathway: __B__Neurotransmitter __A__Growth factor __B__ Hormones __B__ Yeast mating factors • Receptor tyrosine kinase • G-protein-linked receptor

17. When does transduction begin? • Which molecules are the most common second messengers?

18. When does transduction begin? • When the signal molecule binds to the receptor protein and changes in the protein in some way • Which molecules are the most common second messengers? • cAMP • Calcium ions

19. Explain the role of the following enzymes: • Protein kinase • Protein phosphatase • Adenylylcyclase • Phosphodiesterase • Phospholipase C • Explain the role of the following second messengers: • cAMP • IP3 • Calcium ions

20. Explain the role of the following enzymes: • Protein kinase • Transfers phosphate groups from ATP to a protein • Protein phosphatase • Removes phosphate groups from proteins • Adenylylcyclase • Converts ATP to cAMP • Phosphodiesterase • Converts cAMP to AMP • Phospholipase C • Cleaves a plasma membrane phospholipid into DAG and IP3

21. Explain the role of the following second messengers: • cAMP • Activates a protein kinase • IP3 • Binds to a ligand-gated ion channel in the ER • Opens the channel and allows calcium to flow from ER to cytosol • Calcium ions • Increased concentrations cause various responses • Ex: muscle contraction, secretion of substances, cell division

22. Explain the phosphorylation cascade model. • How is cAMP made? (Explain the process.)

23. Explain the phosphorylation cascade model. • Signal molecule binds to receptor • Receptor passes signal to relay molecule • Relay molecule activates protein kinase 1 • Active protein kinase 1 transfers a phosphate from ATP to inactive protein kinase 2 • Activates PK2 • Protein kinases are activated throughout the entire phosphorylation cascade • Final protein kinasephosphorylates a protein that causes the cell’s response to the signal

24. How is cAMP made? (Explain the process.) • First messenger (signal molecule) binds to receptor protein • Receptor protein activates G protein by hydrolyzing GDP to GTP • Activated G protein activates the adenylylcyclase enzyme • ATP is converted into cAMP • Camp activates protein kinase

25. Explain how the cholera bacteria (Vibriocholerae) disrupts a G protein signal transduction pathway. • Where are calcium ion concentrations highest?

26. Explain how the cholera bacteria (Vibriocholerae) disrupts a G protein signal transduction pathway. • Cholera bacteria produces a toxin • Toxin modifies G protein • G protein can’t hydrolyze GTP back to GDP • So pathway is always active • cAMP is constantly being made • High levels of cAMP in intestinal cells cause lots of water and salt to be secreted • Where are calcium ion concentrations highest? • Outside the cell (interstitial fluid) or inside the ER

27. Explain how calcium ions are released from the ER (know the entire process). • What are the two types of responses (the last step of the signal transduction pathway—where do they occur)?

28. Explain how calcium ions are released from the ER (know the entire process). • Signal molecule binds to receptor protein • Receptor protein activates G protein • G protein activates Phospholipase C • Phospholipase C cleaves a membrane protein into DAG and IP3 • IP3 travels through cytosol to ER • IP3 binds to an IP3-gated calcium channel in the ER’s membrane • Causes ion channel to open and release calcium into the cytosol • What are the two types of responses (the last step of the signal transduction pathway—where do they occur)? • Nucleus and Cytoplasm

29. What are scaffolding proteins? • How is the signal in a signal transduction pathway “turned off”?

30. What are scaffolding proteins? • Large relay proteins to which several other relay proteins are simultaneously attached • Increases signaling efficiency • How is the signal in a signal transduction pathway “turned off”? • Signaling molecule dissociates from receptor protein • Receptor protein reverts to inactive form which causes all other parts of the pathway to become inactive again

31. Match the following terms with their correct definition. ____Conformer ____Homeostasis ____Interstitial fluid ____Regulator ____Thermoregulation • Internal environment that exchanges nutrients and wastes • Internal balance • Moderates internal conditions as external conditions change • Allows internal conditions to vary with certain external conditions • Process by which animals maintain an internal temperature, within a tolerable range

32. Match the following terms with their correct definition. __D__Conformer __B__Homeostasis __A__Interstitial fluid __C__Regulator __E__Thermoregulation • Internal environment that exchanges nutrients and wastes • Internal balance • Moderates internal conditions as external conditions change • Allows internal conditions to vary with certain external conditions • Process by which animals maintain an internal temperature, within a tolerable range

33. Explain how a negative feedback loop works. Give an example. • Explain how a positive feedback loop works. Give an example.

34. Explain how a negative feedback loop works. Give an example. • A change in a variable being monitored triggers a response that counteracts the initial fluctuation • Ex: body temperature, blood glucose levels • Explain how a positive feedback loop works. Give an example. • A change in a variable triggers mechanisms that amplify the change • Ex: childbirth, breast feeding

35. _________________ (Ectotherms or Endotherms) gain most of their heat from their environment. _________________ (Ectotherms or Endotherms) can use metabolic heat to regulate their body temperature.

36. ___Ectotherms____ (Ectotherms or Endotherms) gain most of their heat from their environment. ___Endotherms ___ (Ectotherms or Endotherms) can use metabolic heat to regulate their body temperature.

37. Explain how the mechanism of homeostasis works (**hint: think receptor, control center, effector). • What is the set point in a homeostatic mechanism?

38. Explain how the mechanism of homeostasis works (**hint: think receptor, control center, effector). • Receptor detects a change in some variable • Control center processes information it receives and directs an appropriate response • Effector carries out the desired response • What is the set point in a homeostatic mechanism? • The point of homeostasis; the point around which the system is based

39. Which part of the brain controls thermoregulation? This part of the brain contains nerve cells that function as our body’s “thermostat”. • List the types of local regulators.

40. Which part of the brain controls thermoregulation? This part of the brain contains nerve cells that function as our body’s “thermostat”. • Hypothalamus • List the types of local regulators. • Neurotransmitters • Cytokines • Growth factors • Nitric acid • Prostaglandins

41. Why do cells react differently to the binding of the same signal molecule? • List three characteristics of a hormone.

42. Why do cells react differently to the binding of the same signal molecule? • Signaling pathways can use different proteins • List three characteristics of a hormone. • Secreted into extracellular fluid • Carried by circulatory system • Communicates messages within the body • Travel throughout the entire body