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The Cell Membrane

This agenda covers the structure and function of the cell membrane, including lipid bilayers, transmembrane proteins, cholesterol, and glycolipids. It also includes instructions for an egg lab exploring different types of solutions.

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The Cell Membrane

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  1. The Cell Membrane Structure and Function

  2. Agenda: 5/6 • Grab a paper from the basket! • Order of Operations: • Egg Lab / Types of Solutions mini poster • Finish test (in computer lab) • Cell Transport Notes (from website) • Time for vocab project • Reminders: Mock EOC on Thursday, 3rd section of vocab project due 5/24!

  3. Cell Membrane Functions • Cell membrane surrounds the cell, regulating the transport of materials into and out of the cell

  4. Cell Membrane Structure • Lipid Bilayer: a double layer of phospholipids that make up the cell membrane

  5. Phospholipid • Phosphate Head: • Polar • Hydrophilic (attracted to water) • Two Fatty Acid Tails: • Nonpolar • Hydrophobic (avoids water) • Two Layers • Outsides: Polar Heads • Inside: Nonpolar Tails

  6. Other lipids ? • Lipids • Fatty acids • Fats and waxes • Steroids • Cholesterol • Testosterone

  7. Cell Membrane Structure • Phospholipids are arranged so hydrophilic (water loving) ends face outside and hydrophobic (water fearing) tails create the interior

  8. Cell Membrane Structure • Phospholipid Bilayer • Transmembrane Proteins • Cholesterol (a steroid) • Glycoprotein and Carbohydrate

  9. Cell Membrane Structure • Transmembrane Proteins • Job: • Attachment point between cells • Anchor cell in place • Create channels for large and/or polar molecules to pass

  10. Cell Membrane Structure • Cholesterol • Job: • Maintains fluidity of cell membrane

  11. Cell Membrane Structure • Glycolipids and Carbohydrates • Job: • Serve as cell markers for identification

  12. Cell Membrane Structure • The Fluid Mosaic Model • The membrane is dynamic – molecules are constantly moving

  13. Selectively Permeable • The cell membrane is selectively permeable, meaning some substances can pass through the cell membrane, but others can’t! • “Permeable” is the ability for something to pass through

  14. You are working on one or the other! EGG LAB INSTRUCTIONS TYPES OF SOLUTIONS • Strain egg over sink • Rinse egg and cup • Make observations about egg on lab paper • Place egg back in cup and pour syrup over the egg • Replace plastic wrap and place cup on back counter • Wipe tables down with Clorox wipes and WASH YOUR HANDS! • For each type of solution, WRITE THE TERM, DEFINE THE TERM, and then draw the ANIMAL CELL and the PLANT CELL on page 186 in the GREEN BIO textbook. • Make sure to label the direction(s) that water is moving!

  15. Passive Transport Osmosis and Diffusion

  16. Selectively Permeable • The cell may transport substances • Passive Transport: No Energy required • Active Transport: Uses energy (ATP)

  17. Passive Transport • Movement of a substance into/out of a cell without using energy • HIGH  LOW concentration • 3 Types • Simple Diffusion • Facilitated Diffusion • Osmosis

  18. About Concentration… • We just learned that substances move from HIGHLOW concentration in passive transport…but what do we mean by concentration? • Means amount dissolved in a container • How do you like your sweet tea? a. Unsweet (low concentration of sugar) b. Sweet c. Super sweet(high concentration of sugar) • Solute = Substance dissolvedin water

  19. Concentration Gradients • A concentration gradient is the difference in the concentration, or amount, of something in a space • In the box below, the dots have a higher concentration on the left than the right, so they begin movement to the right • When the concentration gradient is the same throughout the area, it is ina dynamic equilibrium • Particles are moving from one side to the other, but at the same rate. Picture: www.hartnell.edu

  20. Passive Transport: Diffusion • Diffusion is when a substance moves from an area of high concentration to low concentrationarea • Diffusion will continue until balanced/equal “at equilibrium”

  21. Facilitated Diffusion • Diffusion of large molecules through special protein channels • Ex. Ions, glucose • Still happens without energy being used!

  22. Passive Transport: Osmosis • Osmosisis the diffusion of water across a selectively permeable membrane • Water moves from an area of high concentration (lots of water) to low concentration (little water) • Passive Transport: • Water moves with its concentration gradient • No energy is required Picture: scienceaid.co.uk

  23. About Osmosis • Water can move into or out of the cell, depending on the environment (solution) that the cell is in • Solvent + Solute = Solution • Solvent does the dissolving (ex. Water) • Solute substance dissolved(ex. Salt)

  24. Describing Solutions

  25. How Osmosis Works

  26. Osmosis • Onion in Salt Water • Blood Cells Same Swelling Shrinking Picture: www.peoi.org

  27. Check for understanding • After an ice storm, road crews salt the roadways to melt ice and increase traction for cars. • What happens to the plants on the side of the road? Explain why.

  28. Isotonic, Hypotonic, or Hypertonic? 10% NaCL Environment 90 % H2O CELL 10% NaCL 90 % H2O

  29. Water Goes? • Isotonic-Water goes in/out (balanced); cell stays the same! 10% NaCL Environment 90 % H2O CELL 10% NaCL 90 % H2O

  30. Isotonic, Hypotonic, or Hypertonic? 10% NaCL Environment 90 % H2O CELL 20% NaCL 80 % H2O

  31. Water Goes? • Hypotonic-water goes IN! Cell swells! 10% NaCL Environment 90 % H2O CELL 20% NaCL 80 % H2O

  32. Isotonic, Hypotonic, or Hypertonic? 10% NaCL Environment CELL 5% NaCL

  33. Water Goes? • Hypertonic-water goes OUT-Cell Shrinks!! 10% NaCL Environment Often, you will just be given the solute concentration in the environment. What is the water concentration? Would it move in or out? CELL 5% NaCL

  34. Active Transport Movement Requiring Energy

  35. Active Transport • Molecules move across the membrane AGAINST their concentration gradient • Moving LOW to HIGH • ENERGY is required! (imagine trying to push your way through a crowd vs. going with the flow…) • Two Types • Protein Pumps • Bulk Transport

  36. Protein Pumps • Transport small molecules/ions AGAINST their concentration gradients • (LOW HIGH) • Uses ATP (cell energy) Notice the ATP

  37. Bulk Transport • Larger molecules (proteins, starch) are transported by vesicles that merge with the cell membrane • Exocytosis-contents leaving the cell through the membrane • Endocytosis-contents entering in vesicles (pinocytosis and phagocytosis)

  38. Finish up egg lab! • Strain egg liquid over sink • Throw away cup in big trash can • Place egg in a bowl and take it back to your seat! • Finish lab observations /definitions / conclusion / questions and turn in! • When finished with egg, throw it away in big trash can!

  39. Egg Lab Procedure • Pour liquid through strainer over sink • Pour as little of the syrup into the sink as possible! • Throw away cup with syrup (into big trash can) • Label a new cup with names of group members • Make observations about egg and place in new cup • Pour distilled water gently over the egg and place plastic wrap back over cup • While you are waiting for a sink: • Work on Cells Review Notes and Labeling • Work on Types of Solutions assignment from yesterday

  40. Homeostasis Lab • Groups 2-3 (NO MORE THAN 3!) • One person will volunteer to do jumping jacks and have vitals measured a certain points in the experiment. • Heart rate • Breathing rate • Perspiration level • Record data, answer lab questions with partner(s) • Graph if we have time???

  41. Homeostasis Maintaining Balance

  42. Homeostasis • The process by which an organism’s internal environment is kept in equilibrium (stable) in spite of changes in the external environment • Examples: • Internal Temperature • Sweating removes excess body heat • Shivering increases heat production • Water balance • Kidneys adjust water amount in urine • A physical response to stress • Breathing/heart rate increases • Pupils dilate • Sweating)

  43. Homeostasis • Homeostasis requires energy • For active transport to deliver needed molecules • T0 rid cell of toxins • To move to avoid danger or find food

  44. Homeostasis in Cells Cells can maintain homeostasis in a number of ways… • Controlling substances that cross the membrane • Active and Passive transport)

  45. Homeostasis in Cells Cells can maintain homeostasis in a number of ways… • Buffers • Cells produce buffers to help maintain a constant pH. • Examples: • Human blood cells must maintain a pH of 7.35-7.45 • Cells in stomach maintain a pH of 3 • Cells in Small Intestine maintain a pH of 6 • What is a buffer? • A chemical that can raise or lower the pH(it can behave like an acid or a base)

  46. Yolk

  47. Egg in Syrup Layer of water over the syrup

  48. Poured egg into strainer Water / syrup into trash Notice wrinkled appearance of egg

  49. Notice decreased size of egg Syrup

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