AP Biology - Oikos



Ms. Day/ AP Biology Name _________________________

Cell Communication Reading Guide Worksheets

This chapter is often considered difficult as you have not covered it in your introductory biology course. Plan on reading this chapter at least twice and go slowly. I would suggest that you read the key concepts in bold first and then for each concept, look at the headings, then the figures and then read.

1. What is a signal transduction pathway?

2. Explain the two types of local signaling:

a. Paracrine signaling

b. Synaptic signaling

3. How are long distance signals sent?

4. Define the three stages of cell communication:

a. Reception

b. Transduction

c. Response

5. What is a ligand?

6. Where would you expect most water soluble messengers to bind and why?

7. What is a G-protein-linked receptor?

8. What is a kinase?

9. How is a tyrosine kinase receptor is different from a G-protein linked receptor?

10. What is a signal transduction pathway?

11. What are phosphorylation cascades?

12. What are second messengers and what are two characteristics of a second messenger?

13. Complete the diagram below of cAMP as second messenger:

[pic]

14. What are ion-channel receptors?

15. How is signal amplification accomplished in the cell?

16. How is specificity accomplished in cell signaling?

17. How is termination of a signal accomplished and why is it so important that termination be accomplished?

Ms. Day/ AP Biology Name _________________________

Cell Communication Reading Guide Worksheets

This chapter is often considered difficult as you have not covered it in your introductory biology course. Plan on reading this chapter at least twice and go slowly. I would suggest that you read the key concepts in bold first and then for each concept, look at the headings, then the figures and then read.

1. What is a signal transduction pathway? Give an example

2. How do intercellular connections function in cell to cell communication?

3. Explain the difference between paracrine and synaptic signaling.

4. How are long distance signals sent? Give an example in the body

5. How do nerve cells provide example of both local and long distance signaling?

6. A signal transduction pathway has three stages. Use Figure 11.6 to label the missing parts of the preview figure below, and then explain each step.

[pic]

Receptor:

Transduction:

Response:

7. Explain the term ligand. Give an example of how a ligand is used.

8. Fill-in the chart below regarding the 3 types of membrane receptors:

|Receptor |How it functions as a receptor |Example |

|G-Protein | | |

|Tyrosine Kinase | | |

|Ion Channel | | |

9. What does conformation mean?

10. In what body system are ligand-gated ion channels and voltage-gated ion channels of particular importance?

11. How are intracellular receptors unique? Give an example.

12. Where would you expect most water soluble messengers to bind and why?

13. How are phosphorylation cascades similar to a row of dominoes falling down?

14. Explain the role of these enzymes in transduction:

a. protein kinase

b. protein phosphatases

15. What is the difference between a first messenger and a second messenger?

16. Complete the diagram below of cAMP as second messenger:

[pic]

17. Explain the role of the second messenger cAMP.

18. When cell signaling causes a response in the nucleus, what normally happens?

19. When cell signaling causes a response in the cytoplasm, what normally happens?

20. How does the disease cholera connect with the concepts of cell to cell communication?

21. Explain how very little epinephrine can have a rapid response in the body.

22. How is signal amplification accomplished in the cell?

23. How is specificity accomplished in cell signaling?

24. What is a scaffolding protein and why is it important?

25. How is termination of a signal accomplished and why is it so important that termination be accomplished?

How does caffeine affect the body?

Biologist Neal J. Smatresk--Dean of the College of Science at the University of Texas at Arlington--offers this explanation:

Caffeine--the drug that gives coffee and cola its kick--has a number of physiological effects. At the cellular level, caffeine blocks the action of a chemical called phosphodiesterase (PDE). Inside cells, PDE normally breaks down the second chemical messenger cyclic adenosine monophosphate (cAMP). Many hormones and neurotransmitters cannot cross the cell membrane, and so they exert their actions indirectly via such second messengers; when they bind to a receptor on the surface of a cell, it initiates a chemical chain reaction called an enzyme cascade that results in the formation of second messenger chemicals.

Historically, cAMP was the first second messenger ever described. Now, however, scientists have identified several major classes of second messengers, which are generally formed in similar ways through a set of molecules called G proteins. The advantage of such a complex system is that an extracellular signal can be greatly amplified in the process, and so have a massive intracellular effect.

Thus, when caffeine stops the breakdown of cAMP, its effects are prolonged, and the response throughout the body is effectively amplified. In the heart, this response prompts norepinephrine--also called noradrenalin--and a related neurotransmitter, epinephrine, to increase the rate and force of the muscle's contractions. Although the two act in concert, norepinephrine is released by sympathetic nerves near the pacemaker tissue of the heart, whereas epinephrine is released primarily by the adrenal glands. These chemical messages lead to "fight or flight" behavior. During stressful or emergency conditions, they raise the rate and force of the heart, thereby increasing the blood pressure and delivering more oxygen to the brain and other tissues.

Caffeine would be expected to have this effect on any animals that used these neurotransmitters to regulate their heartbeat. Generally speaking, the effects of caffeine are most pronounced in birds and mammals. Reptiles have some response, and lower vertebrates and invertebrates have rather small or no responses. From an evolutionary perspective, fish and amphibians don't show as strong a response to epinephrine and norepinephrine as the higher vertebrates, and they lack a well-developed sympathetic (that is, stimulatory) enervation to heart.

How Does Caffeine Affect the Body? Article Questions



1). What is caffeine?

2.) What kinds of substances contain caffeine? Name at least 2.

3.) How does caffeine interfere with a signal transduction pathway in your body? Be specific! Use names of enzymes that caffeine interferes with in your answer.

4.) What is cAMP?

5.) How is cAMP and caffeine connected?

6.) What is norepinephrine?

7.) How is norepinephrine and caffeine connected?

8.) What is the “fight or flight” behavior?

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