Cell Membrane. The cell membrane is flexible and allows a unicellular organism to move

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1 Cell Membrane Outer membrane of the cell to protect its contents Regulates the molecules that pass in and out of the cell (selectively permeable) Give the cell its shape

2 Cell Membrane Outer membrane of the cell to protect its contents Regulates the molecules that pass in and out of the cell Give the cell its shape Maintains Homeostasis

3 Cell Membrane The cell membrane is flexible and allows a unicellular organism to move

4 Cellular Homeostasis Cells subject to constant changes Must keep internal concentrations of substances like water, glucose, proteins, ions, & nutrients at a constant level, while eliminating waste The cell does this through the cell membrane because it is selectively permeable

5 Fluid Mosaic Model FLUID- because individual phospholipids and proteins can move around freely within the layer, like it s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above.

6 This model is described as a phospholipid bilayer with proteins embedded in this double layer. Structural Components: 1. Phospholipids 2. Integral/Channel proteins 3. Receptor/Peripheral proteins 4. Marker/Glyco proteins 5. Carbohydrate chains 6. Cytoskeleton 7. Cholesterol

7 Phospholipids Each phospholipid has a head & tails Head phosphate group PO 4 Tails - lipids

8 Membrane Components Proteins (peripheral and integral)

9 Phospholipid Bilayer Each phospholipid is an individual unit that is electrically attracted to another phospholipid. These units line up beside each other to form a barrier. They are not connected! (Think bobbing for apples) A double layer is formed, with the internal layer inverted (upside down)

10 Embedded Proteins 3 types: 1. Channel/Integral Proteins act as the gateways in/out of the cell for transporting large food molecules, waste, & other molecules each gate only allows passage of certain items. How can these proteins be selectively permeable?

11 2. Receptor/Peripheral Proteins communication link between the inside of the cell & the outside world 3. Marker/Glyco protein identifies the kind of cell & that the cell belongs to that organism name tag that says heart cell belonging to John The tag itself is a carbohydrate chain connected to the protein. Why do your cells need name tags?

12 Diffusion The net movement of particles (liquid or gas) from an area of high concentration to an area of low concentration. No energy is required for these particles to move

13 Diffusion An obnoxious individual with a lit cigar gets on an elevator on the 3 rd floor with the cigar still burning. You are unfortunate to be in a tall building and he comments, Hey we are both going to the 62 nd floor! What are some of your own examples of diffusion?

14 Diffusion Dynamic equilibrium

15 Diffusion of Liquids

16 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW)

17 Osmosis The movement of water across a selectively permeable membrane from from high concentration to low concentration. Water moves down the concentration gradient No energy (ATP) is required from the cell

18 Diffusion of H 2 O Across A Membrane/ OSMOSIS Dynamic Equilibrium HIGH CONCENTRATION to LOW CONCENTRATION

19 Osmosis Illustration Osmosis.htm Environment surrounding a cell determines whether water will enter the cell or leave the cell.

20 Cells in Solutions

21 Osmosis in Red Blood Cells Red Blood cell swelled & broke (lysed)

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23 Remember:Diffusion does NOT require energy (ATP)

24 However, some types of movement across cell membrane do require energy (ATP): Active Transport -Requires energy (ATP) WHY??? -Moves materials from LOW to HIGH concentration -AGAINST concentration gradient EX. PUMPS, Endocytosis, Exocytosis

25 Active transport v Examples: PUMPS Pumping Na + (sodium ions) out and K + (potassium ions) in against strong concentration gradients. v Called Na+-K+ Pump

26 Active Transport cont Endocytosis moving the big things in Ex. Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.

27 Active Transport cont Pinocytosis (specific type of endocytosis) Most common form of endocytosis. Takes in dissolved molecules as a vesicle.

28 Pinocytosis Cell forms an invagination Materials dissolve in water to be brought into cell Called Cell Drinking

29 Transport across a capillary cell (blue). Example of Pinocytosis pinocytic vesicles forming mature transport vesicle

30 Active transport cont Phagocytosis (specific type of endocytosis) Used to engulf large particles such as food, bacteria, etc. into vesicles Called Cell Eating

31 Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)

32 Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Extracellular Environment

33 Moving the Big Stuff out Exocytosis - moving things out. Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. This is how many hormones are secreted and how nerve cells communicate with one another.

34 Moving the Big Stuff