BIOH111 [SESSION 2] Tutorial- CELL PLASMA MEMBRANE/CELL TRANSPORT Learning Outcomes: Define steps of central dogma nd describe each process. Define the basic components of the plasma membrane Describe types of membrane proteins and define their structure and function Define types of transport across cell membranes and describe their functions Activity 1: Build-a-Membrane Background: Cell membranes are made of phospholipid molecules that arrange themselves into two rows called a bilayer. Proteins are embedded in the phospholipid bilayer, through one or both layers. These proteins help other molecules cross the membrane and perform a variety of other functions. Activity: Create your own model of a small section of cell membrane by following the instructions below: 1. Cut out the phospholipid bilayer (page S2) along the solid lines. Cut all the way to the edges of the paper in the direction of the arrows. 2. Fold the phospholipid bilayer along the dotted lines and tape the edges together to form a fully enclosed rectangular box 3. Cut out each protein (pages S3 & S4) along the solid black lines and fold along the dotted lines. 4. Form a 3-D shape by joining the protein sides and tops together and tape them in to please. 5. Tape the 3-D proteins into place along the edges of the phospholipid bilayer. 6. By staggering the transmembrane proteins back and forth along both long sides of the bilayer box, the whole model stand by itself on a table. Last updated on 30-Jan-18 Page 1 of 10
Activity 2: Osmosis experiment The aim of this experiment is to observe the effects of the movement of water into and out of cells (Osmosis). Materials required: 1 Potato tuber Two clear glass containers (jars or glasses will be appropriate) Salt solution (made from water and one (1) tablespoon of table salt per 100mls) Distilled water Methods: Peel the potato and cut two 2cm cubes. Place one potato cube into a glass of distilled water and the other into a glass of salt solution. Leave the potatoes in the solution for 20 to 30 minutes. Take the potatoes out of the solutions and observe the different effects of the two solutions. Results: 1. What has happened to the potato cubes? - Potato in salt solution? - Potato in distilled water? 2. Give a detailed description of the results you have obtained. How do your results illustrate the concept of osmosis? (max 200 words) Last updated on 30-Jan-18 Page 2 of 10
3. If you use boiled potatoes instead of raw ones, would you expect to observe similar effects? Why? Activity 3: Go to the following website: https://www.spongelab.com/index.cfm Lesson 1 1. In the search bar type Gene Expression- The Basics 2. Click on the title under Games and Simulations 3. Then click on Launch Interactive 4. Click on Click to Run 5. Then click on Open with (Java Web Start Launcher (default) and click OK 6. If this box comes up click Run 7. Complete the activity Lesson 2 1. Enter Translation into the Search Bar 2. Click on Animations and Video 3. Click on Translation Virtual Cell 4. Click on View on the left hand side of the page Last updated on 30-Jan-18 Page 3 of 10
Lesson 3 1. Enter Translation into the Search Bar 2. Click on Animations and Video 3. Click on DNA Translation (advanced detail) 4. Click on View on the left hand side of the page Activity 4: Go to the following website and launch the cell transcription and translation activity. Watch the Overview, Transcription and Translation sections. Go to the following website, launch the DNA Workshop and complete the interactive http://www.pbslearningmedia.org/resource/lsps07.sci.life.stru.celltrans/cell-transcription-andtranslation/ activities:http://www.pbslearningmedia.org/resource/tdc02.sci.life.gen.dnaworkshop/dnaworkshop/ Activity 5: Answer the following questions: 1. What does the Central Dogma of Molecular Biology explain? 2. Gene expression has two key stages, transcription and translation. Define and outline what happens at each of the 3 steps in each of these processes. Last updated on 30-Jan-18 Page 4 of 10
Activity 6: 1. List and describe the 2 different classifications of membrane proteins. 2. Complete the following table by inserting the name of the protein, function and classification. Membrane protein Function Integral and/or Peripheral Last updated on 30-Jan-18 Page 5 of 10
Activity 7: Copy and paste the below web address to your browser: http://www.wiley.com/college/pratt/0471393878/student/animations/membrane_transport/ind ex.html Watch the animations related to cell membrane transport (10-15 min), then identify the passive transport processes described below from the given list. a. Net movement of any substance (such as cocoa powder) from a region of high concentration to a region of lower concentration b. Movement of non-polar molecules (such as O 2, CO 2, steroids and vitamins A and D) across the lipid layer of the plasma membrane c. Process that does not require an integral membrane protein d. Glucose transport mechanism e. Transport of polar chemicals (such as K +, Na +, or Cl-); may be gated or not carrier-mediated channel-mediated simple diffusion Last updated on 30-Jan-18 Page 6 of 10
Possible final exam questions (Cell biology): Central dogma describes two (2) cellular processes transcription and translation. Each of these processes has three (3) steps. First define what is the result of these two processes, then name the three (3) steps that happen in both and finally describe the process of transcription and translation in order they occur. Glucose levels in the blood are tightly regulated by transporters present on the plasma membranes of the cell. Because of this tight regulation the cell uses two transport mechanisms that allow glucose to enter the cell facilitated diffusion and active transport. Explain the difference between these two transport processes by describing the examples of glucose transport across the plasma membrane. Cell regulates molecule concentration across the membrane by using active transport process and ion channels. Explain active transport that ensures homeostasis of glucose and calcium ions across the membrane using Na + /glucose symporter and Na + /Ca +2 antiporter as examples. Last updated on 30-Jan-18 Page 7 of 10
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