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The Cell Membrane. What is the cell membrane?. AKA: Plasma membrane The boundary between the cell and the environment Does every cell have a cell membrane? Yes, Each and every cell has a cell membrane. Cell membranes help maintain homeostasis, what is that?. Cells breathing

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The Cell Membrane

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The cell membrane l.jpg

The Cell Membrane


What is the cell membrane l.jpg

What is the cell membrane?

  • AKA: Plasma membrane

  • The boundary between the cell and the environment

  • Does every cell have a cell membrane?

    • Yes, Each and every cell has a cell membrane.


Cell membranes help maintain homeostasis what is that l.jpg

Cell membranes help maintain homeostasis, what is that?

  • Cells breathing

  • Cells getting blood to them

  • Cells maintaining internal conditions

  • Cells reproducing


How do cell membranes help to maintain homeostasis l.jpg

How do cell membranes help to maintain homeostasis?

  • The cell membrane allows nutrients to come into the cell

    • Glucose, amino acids, lipids

  • The cell membrane removes waste


  • Selective permeability l.jpg

    Selective Permeability

    • The cell membrane lets some molecules in and keeps others out

    • EX. A cell is low on glucose so the membrane lets in some glucose, but does not overfill the cell with the macromolecule.


    Structure of the cell membrane l.jpg

    Structure of the cell membrane

    • What does the cell membrane look like up close?

    Lets look at one of these structures up close


    Structure of cell membrane l.jpg

    Structure of cell membrane

    • Phospholipids

      • Phosphate head

      • Glycerol

      • 2 Fatty acid tails(lipids=fats, oils, etc)


    Phospholipids l.jpg

    Phospholipids

    • 1.) Phosphate Head

      • Polar

      • Hydrophilic

      • Make up the outer borders of the membrane

  • 2.) Fatty Acid Tails

    • Nonpolar

    • Hydrophobic

    • Make up the inner part of the membrane


  • Structure of phospholipid l.jpg

    Structure of Phospholipid


    Polar vs nonpolar l.jpg

    Polar vs. Nonpolar

    Polar- positive and negative ends (b/c electrons are not shared equally)

    Ex. Water

    Nonpolar- does not have oppositely charged ends (atoms share electrons equally)


    Why are the phospholipids arranged tail to tail l.jpg

    Why are the phospholipids arranged tail to tail?

    -b/c water is inside and outside the cell

    phosphate group is hydrophilic (polar) end

    -attracts water

    fatty acid tail end is hydrophobic (nonpolar)

    -repels water


    Structure of cell membrane12 l.jpg

    Structure of cell membrane

    • Phospholipid bilayer

      • 2 layers of phospholipids make up a cell membrane


    Phospholipid bilayer l.jpg

    Phospholipid Bilayer

    • Remember polar heads and nonpolar tails


    Arrangement of phospholipids tail to tail l.jpg

    Arrangement of phospholipids “tail to tail”


    Arrangement of phospholipids tail to tail due to water inside outside the cell l.jpg

    Arrangement of phospholipids “tail to tail” due to water inside & outside the cell


    When something is hydrophilic it l.jpg

    When something is hydrophilic, it…

    • Has a chemical makeup that likes to be around water

    • Has a chemical makeup that does not like to be around water


    Where would you expect to find water in this cell membrane l.jpg

    Where would you expect to find water in this cell membrane?

    • Here

    • Here


    Other components of the cell membrane l.jpg

    Other components of the cell membrane

    • Cholesterol

      • Helps to stabilize the phospholipids and keep them from sticking together


    Other components of the cell membrane19 l.jpg

    Other components of the cell membrane

    • Proteins

      • Regulate which molecules enter and which molecules leave a cell.


    Types of proteins in the cell membrane l.jpg

    Types of proteins in the cell membrane

    • Carrier Protein

      • Allow needed substances or waste materials to move through the cell membrane


    Types of proteins in the cell membrane21 l.jpg

    Types of proteins in the cell membrane

    • Channel or Pore protein

      • Hydrophilic channel – allows lipid insoluble substances to pass in and out of cell.


    Types of proteins in the cell membrane22 l.jpg

    Types of proteins in the cell membrane

    • Glycoproteins

      • Protein with what macromolecule attached to it?

        • Carbohydrate

      • Functions for cell to cell recognition


    Types of proteins in the cell membrane23 l.jpg

    Types of proteins in the cell membrane

    • Receptor Protein

      • These have binding sites for molecules such as hormones or substrates to bind to


    Fluid mosaic model of cell membrane l.jpg

    Fluid Mosaic Model of Cell Membrane

    -lipid bilayer is not strong & firm like a hard shell, but it is fluid like a soap bubble (often called a fluid mosaic model)

    -individual phospholipids, arranged side by side, float within the bilayer (cholesterol prevents phospholipids from sticking together)


    Structure of cell membrane25 l.jpg

    Structure of Cell Membrane

    -nonpolar interior zone- true barrier that separates the cell from its surroundings

    many polar particles like sugars, proteins, ions, & most cell wastes cannot cross this zone b/c they are repelled by the nonpolar region


    Arrangement of cell surface proteins l.jpg

    Arrangement of cell surface proteins


    Cell membrane structure l.jpg

    Cell Membrane Structure


    Lets build a cell membrane together l.jpg

    Lets build a cell membrane together

    • http://www.wisc-online.com/objects/index_tj.asp?objid=AP1101


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