Cell+Transport


 * Transport into and out of the cell begins with the cell membrane.**

**Activity One** The cell membrane (sometimes called the plasma membrane) is responsible for a number of important functions in the cell. On [|this site,] you will find the information you need to answer the following questions:



1. The lipid bilayer is referred to as a mosaic. What is meant by this? 2. The cell membrane is a fluid mosaic of what three biomolecules? 3. What are the major components of the cell membrane? 4. Describe the fluid nature of the cell membrane. 5. How does cholesterol fit into the structure of the cell membrane? 6. The cell membrane is amphipathic. What does this mean? 7. How does temperature affect the fluid nature of the cell membrane? 8. How does the interior of the double membrane differ from the outside? 9. Name the three classes of lipids. 10. Fats are composed of what two smaller molecules? 11. How can you distinguish between a saturated fat and an unsaturated one? 12. What are glycolipids? 13. What are glycoproteins? 14. Describe the two types of membrane proteins. 15. What is the difference between a fat and a phospholipid? **Activity Two** Log onto this [|cell activity] site.

1. If the cell membrane is hydrophobic, how does water, which is essential not only to the maintenance of the cell but to life itself, cross the cell membrane? 2. What function does cholesterol serve? 3. Answer the interactive questions.

[|This site] offers a comprehensive look at the plasma membrane and the functions of its various components.

Take another [|quiz.] This one is so easy even I can do it!

**Activity Three**
 * Transport Across the Cell Membrane

Diffusion

Imagine that your teacher has opened a bottle of perfume at her desk. How is it possible that you are able to smell the perfume in only a minute or two? Or imagine Mom frying bacon on Saturday morning.......how is it possible that you are able to smell it strongly enough in your room that you wake up from a deep sleep? If you said the smell [|diffuses] through the air until it reaches you, you are correct! Diffusion can occur through the air, through water, across the cell membrane and through certain other media.

Log onto the [|Arizona education site] to begin your study of diffusion across the cell membrane. Answer the following questions:

1. List four requirements that all living things must have in order to sustain life. (We did a unit on this, remember?) 2. Describe the two main ways that molecules move across the membrane. 3. Describe the process of diffusion. 4. Is diffusion active or passive transport? Explain. 5. Describe the two types of equilibrium. 6. How does equilibrium affect diffusion? 7. What factors affect how fast a molecule will diffuse? 8. The cell membrane is selectively permeable. Which molecules diffuse easily across the membrane? 9. How is osmosis different from diffusion? 10. Is osmosis active or passive transport?

Activity Four [|This tutorial] provides additional information about transport across the membrane.** 1. What is a concentration gradient? 2. Does diffusion move with or against the concentration gradient? 3. What two consequences of [|random motion] affect transport across the membrane? 4. If diffusion is a passive process and requires no energy from the cell to take place, what causes particles to move into and out of the cell?

Watch this [|animation] and then take the quiz below.

Watch particles in motion in this [|interactive demonstration.]

Activity Five - Permeability Lab

**Be sure you complete the Permeability Lab analysis**.

Activity Six

Work through this [|interactive tutorial] to learn about how chemicals cross the membrane.

Click on [|this site] to explore membrane proteins, simple diffusion, active transport, and other topics. Scroll down until you find the topic __The__ __Cell Membrane__ and then select all six sites, making notes as needed. Your teacher will give you a worksheet to use for this activity. Also on this site, in the right hand column, is an interactive tutorial entitled The Cell Membrane Tutorial." Click on this site and work through activities 1, 2, 4, 6, 7, 9,11,12,14,and 16.  (These are numbered on the first page at the bottom of the page.)

**Activity Seven**
 * Looking at the image above, explain the difference between active and passive transport in terms of:**


 * **use of proteins in the membrane**
 * **direction of the gradient**
 * **energy use**

Take [|this quiz] on membrane transport and record your answers. Also record your score. Turn in to your teacher. After you have finished, take [|this quiz,] record your answers and your score and turn in to your teacher.


 * Review the phospholipid bilayer for your test:

**

**Activity Eight**
 * Osmosis

Begin with this [|tutorial of osmosis]. Answer the following questions: 1. What is the difference between hydrophobic and hydrophilic? 2. Which part of the lipid bilayer is hydrophobic and which is hydrophilic? 3. Why is the bilayer considered semi (selectively) permeable? 4. Take the quiz. 5. Does osmosis occur with the gradient or against the gradient? How do you know? 6. When does osmosis STOP occurring? 7. Take the quiz. There are [|three tonic states] associated with osmosis. Discover the differences between them. 1. What happens when a cell is exposed to a hypertonic solution? 2. What happens when a cell is exposed to a hypotonic solution? 3. What happens when a cell is exposed to an isotonic solution? 4. Which of the above states does a plant prefer?

Activity Nine - Osmosis Lab Complete the "Osmosis and Concentration Lab" analysis.

Activity Ten [|This site] has good animations showing tho movement of fluids across the cell membrane.

This [|osmosis tutorial] is very student-friendly and self-explanatory.**

a. an isotonic solution b. a hypotonic solution c. a hypertonic solution**
 * Draw a red blood cell that is exposed to


 * [|Take this quiz] as many times as you need to in order to get the correct answers!

Activity Eleven Active Transport This [|Biology4Kids] site has simple information on phagocytosis, pinocytosis and the cooperation of the cell membrane in these processes. 1. What is the difference between phagocytosis and pinocytosis? 2. How are membrane proteins useful in active transport? 3. How is the concentration gradient different in active transport from the gradient in passive transport? 4. How can poisons affect the permeability of the cell membrane? 5. How does phagocytosis take place? 6. Why does phagocytosis take place? 7. Explain the terms pseudopodium and vesicle in relation to endocytosis. 8. What is the role of lysosomes in phagocytosis? 9. What is the purpose of pinocytosis? 10. How does pinocytosis occur? 11. How are vesicles involved in pinocytosis?**


 * Check out this [|animation of phagocytosis].**

Several ions, in particular sodium and potassium, are necessary for the proper maintenance of the cell. Because these ions are often pumped against the concentration gradient, they require energy for this process. Watch this [|animation of the sodium-potassium pump.] Afterward take the quiz that appears after the animation.
 * Activity Twelve **

Find additional information about the Na-K pump on [|this site]. 1. In which kinds of tissues would this pump be more important? 2. How are sodium and potassium pumped, and in what quantities? 3. How much energy is required to "operate" this pump? View this [|animation] of the Na-K pump.

**Activity Thirteen** **Checkpoint charlie: Take [|this quiz] and see how much you know!

[|Quiz on osmosis, cell membrane function, and active transport]. Write down your answers before you check them. Then write down the correct answer if you miss it.**



"How Do Moisturizers Work?" Research this question with regard to the following points: 1. What process allows the uptake of moisturizers through the skin? 2. What chemicals, if any, promote the absorption of moisturizers? 3. What are the effects of absorption of these products? 4. Cite at least three research sources that support your research. Due Date: Thursday, October 8, 2009.
 * EXTRA CREDIT OPPORTUNITY:**



**Activity Fourteen** Review for Test 1. Describe the structure of the cell membrane. 2. What is the purpose of the proteins embedded in the cell membrane? 3. Describe the process of diffusion. 4. Why does diffusion occur? 5. What happens when equilibrium is reached? 6. Describe active transport. 7. Describe passive transport. 8. Describe the process of osmosis. 9. Explain why the cell membrane is said to be "selectively permeable." 10. Describe what will happen to a cell that is placed in a hypotonic solution. 11. Describe what will happen to a cell that is placed in a hypertonic solution. 12. Describe what will happen to a cell that is placed in an isotonic solution. 13. List substances that can pass through the cell membrane and cell wall. 14. Where are membrane proteins produced? 15. Plant cells prefer a hypotonic environment. Why do you think this is true? 16. What would happen if a red blood cell were placed in distilled water? 17. What is facilitated diffusion? 18. What would happen if the cell membrane became impermeable? 19. Suppose a cell were treated with a chemical that inhibits active transport. What would happen? 20. Describe how the sodium-potassium pump helps prevent animal cells from bursting. 21. Compare two ways that the binding of a signal molecule to a receptor protein causes a change in the activity of the receiving cell. 22. During exercise, potassium ions accumulate in the fluid surrounding muscle cells. Which cell-membrane protein helps muscle cells counteract this tendency? Explain your answer. 23. What is a concentration gradient? 24. What is endocytosis? 25. What is phagocytosis? Is it a form of exocytosis or endocytosis? 26. When an amoeba eats a bacterium, it uses structures called the pseudopodia and vesicles; what are these structures in terms of phagocytosis? 27. Describe the process of pinocytosis. 28. How does pinocytosis differ from the process of osmosis? 29. How does phagocytosis differ from the process of diffusion?