Cell Membrane Movement of Substances Into and Out of the Cell Created by Mr. Woodbury & Mrs. Beddes Modified by Mrs. Slater

Cell Membrane Structure  Cells are surrounded by a thin, flexible, selectively permeable membrane.

Selective Permeability  Allows only certain substances to pass through

Fluid Mosaic Model  The membrane is fluid because it is not rigid or fixed like a wall  Fluid in the verb- sense… e.com/watch?v=S pPXewlgmcw e.com/watch?v=S pPXewlgmcw  The parts shuffle, move and flex  The membrane is like a mosaic with the different parts put together  Different parts have different shapes and functions

5 Phospholipids  A phospholipid is made of a 1 polar, hydrophilic head and 2 non-polar hydrophobic tails  Classified as a lipid  The main part of membranes

Cell Membrane Structure  Phospholipid bilayer  Arranged with hydrophilic head on outside and hydrophobic tails on inside

Definitions  Hydrophilic head  Hydro- ≈ water  -philic ≈ loving  Polar regions of a molecule that are attracted to water  Hydrophobic tails  Hydro- ≈ water  -phobic ≈ afraid or hating  Nonpolar regions of a molecule that avoid water or prefer other hydrophobic parts  fatty acid tails

Cell Membrane Structure  Proteins  Enzyme activity, cell-to-cell recognition, cell signaling, transport

Cell Membrane Structure  Cholesterol  Helps to stabilize membrane

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11 Selectively Permeable Cell Membrane Drawing  Draw and label the parts of a cell membrane include phospholipids, proteins, and cholesterol  Draw and label the hydrophobic regions & the hydrophilic regions  Describe/explain each part of the cell  What do phospholipids, proteins, and cholesterol do?  What does hydrophobic & hydrophilic mean?

12 Membranes in organelles  You will be given one of the following organelles to draw.  Since these are all made of membranes, you must draw a large portion of the membrane as the phospholipid bilayer  If it has an outer layer that is made of a membrane, you must draw that as a phospholipid bilayer

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14 Cell Membrane Processes  Cell Transport

15 Cell Membrane Illustration  We will add in the different parts and processes of the cell membrane to this drawing as we go.  First section: the phospholipid bilayer.  Two layers of phospholipids  Hydrophilic heads pointing out and in  Hydrophobic tails pointing towards each other.

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17 Methods of Transport  Transport of materials in and out of the cell falls into two categories  Passive transport  Active transport  Which one sounds like it requires energy?  y4LAkk&feature=related y4LAkk&feature=related

18 Membrane Proteins

19 Passive Transport  Does not require energy from the cell  Type 1: Diffusion  Movement of particles from an area of high concentration to an area of low concentration  Stuff goes from where it is to where it isn’t  Happens because of random movement of particles  Examples: Oxygen, carbon dioxide, some water, and lipid-soluble substances (non- polar molecules)

20 O2O2 CO 2

21 Diffusion… High to Low  To determine which direction material will go, you must know the amounts/ratios/percentages of materials in the different areas.  Water coloring example  Coloring first went to bottom (high concentration)  Then slowly diffused through water (low concentration)  High to low = passive transport

22 A Special Condition  Equilibrium  Number of molecules moving in one direction is equal to the number moving in the other direction  The random motion and collisions are still happening  The net movement in all directions equals out.

23 Passive Transport, cont.  Type 2: Facilitated diffusion  Transport proteins allow the diffusion of certain substances  Channels, tunnels, sometimes with gates  Gates may open & close due to changes in conditions.  Examples: Water, ions and sugars

24 Facilitated Diffusion

25 O2O2 CO 2

26 Passive Transport, cont.  Type 3: Osmosis: Passive transport of water across a membrane  Hypertonic  Solution with a higher solute concentration  Water leaves the cell to dilute the external solution  Isotonic  Solution with an equal solute concentration  No net movement of water (water enters and leaves the cell at the same rate = equilibrium)  Hypotonic  Solution with a lower solute concentration  Water enters the cell to dilute the internal solution

27 Transport Across a Membrane  Video footage: transport.htm transport.htm

How cells behave...

29 Tonicity Flip Diagram  Fold a piece of paper in half hot dog-style  Fold in thirds. Label & draw 1 for each section:  Hypertonic Solution  Inside of the cell: 10% NaCl & 90% water  Outside of the cell (the environment): 15% NaCl & 85% water  Isotonic Solution  Inside of the cell: 10% NaCl & 90% water  Outside of the cell (the environment): 10% NaCl & 90% water  Hypotonic Solution  Inside of the cell: 6% NaCl & 94% water  Outside of the cell (the environment): 3% NaCl & 97% water

30 Flip Diagram – Hypertonic  "HYPER" means more than.  The concentration of solute (salt) outside the cell is greater than that of the solution outside the cell, so water will move out of the cell. Plant cells lose water and start to wilt. Animal cells will shrink / shrivel. In both cases, the cell may die. Overall, the cell size will decrease.

31 Flip Diagram – Isotonic  "ISO" means equal to.  If the concentration of solute (salt) is equal on both sides of the cell membrane, the water will move into the cell, but it won't change the overall amount of water on either side. Humans need isotonic solutions to be at equilibrium which occurs when equal amounts of water are entering and exiting the cell. Overall, the cell size will not change.

32 Flip Diagram – Hypotonic  "HYPO" means less than.  The concentration of solute (salt) inside the cell is greater than that of the solution outside the cell, so water will move inside of the cell. The cell will _____________ water and grow ____________. In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid. In animal cells, the cell may be in danger of ________________. Overall, the cell size will ___________.

Active Transport  Requires energy from the cell  Movement of particles from an area of low concentration to an area of high concentration  Goes “uphill”  Type 1: Pumps  Particle binds to a transport protein  Protein changes shape which requires energy  Releases particle inside the cell  Protein returns to original shape

34 The Sodium- Potassium Pump

35 O2O2 CO 2

Active Transport, cont.  Movement of large particles, using membrane movement/reconfiguration  Type 2: Endocytosis  “Inside + cell + process”  Cell surrounds and takes in material from its environment  Often used for nutrients or foreign invaders  Type 3: Exocytosis  “Outside + cell + process”  Reverse process of endocytosis  Used to expel wastes and secrete substances produced by the cell

Endocytosis Exocytosis

38 Endocytosis & Exocytosis  9lv7eQ

39 O2O2 CO 2

40 Basic types of transport

41 A Summary

42 Membrane Transport Animation  And once again, so you understand what she’s talking about…  ay4LAkk&feature=related ay4LAkk&feature=related

43 Vocab Terms Passive Transport Active Transport Diffusion Equilibrium Facilitated Diffusion Osmosis Hypertonic Isotonic Hypotonic Endocytosis Exocytosis

For the lab  Compare the internal environment of the egg/cell to the liquid it is soaking in.  Interior of cell = water + solutes (stuff)  Exterior of cell = corn syrup or pure water  Which exterior liquid has a higher percentage of water?  Which exterior liquid has a higher percentage of stuff?  Which one was hypertonic?  Which one was hypotonic?  Is your mystery solution hyper-, hypo-, or isotonic?