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The Plasma Membrane

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... are phospholipids containing hydrophilic and hydrophobic parts. Every cell has a plasma membrane. THE PLASMA MEMBRANE ... THE CELL MEMBRANE IS MADE UP OF ... – PowerPoint PPT presentation

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Title: The Plasma Membrane


1
The Plasma Membrane
2
Only 2 molecules thick, this membrane allows the
passage of essential molecules in and out of the
cell.
3
Definition
  • A plasma membrane functions as a selective
    barrier that allows sufficient passage of oxygen,
    nutrients, and wastes to service the entire
    volume of the cell.
  • The plasma membrane is located at the boundary of
    every cell. It is composed of phospholipids and
    proteins
  • The membrane building blocks are phospholipids
    containing hydrophilic and hydrophobic parts.
  • Every cell has a plasma membrane.

4
The plasma Membrane
  • The fluid mosaic model (S.J Singer)
  • it is semi-permeable (some items are allowed in,
    others arent..its picky!)
  • fluid portion is a double layer of phospholipids,
    called the phospholipid bilayer

5
Jobs of the Cell Membrane (think of a police
officer!)
  • To isolate the cytoplasm from the external
    environment.
  • Regulate the exchange of substances into and out
    of the cell.
  • To communicate with other cells.
  • To identify proteins required by the cell.

6
What the Cell membrane is made up of
  • Phospholipids contain a hydrophilic head and a
    non-polar hydrophobic tail.
  • Hydrogen bonds form between the phospholipid
    "heads" and the watery environment inside and
    outside of the cell.
  • Hydrophobic interactions force the "tails" to
    face inward.
  • The heads are hydrophillic (like water)
  • The tails are hydrophobic (afraid of water)

7
DRAW AND LABEL!


8
Layer make-up!
  • The phospholipids are not bonded to each other,
    instead the heads line up beside each other
    packed together like sardines. Because the heads
    are close together, the membrane is said to be
    fluid...it can bend and twist and break off to
    form vesicles.

9
Layer Make-up!
  • The membrane is also super strong thanks to
    cholesterol molecules that are embedded in the
    membrane makes it stronger.

10
So how do Molecules go from the Cytoplasm to the
Extracellular fluid?
11
5 VERY IMPORTANT PROTEINS!
  1. Channel Proteins - form small openings for
    molecules to diffuse through. There are two types
    of channel proteins (open channel proteins and
    gated channel proteins). Similar to a tunnel
    water slide...if the slide is open and you can
    fit...you can go through!

12
Proteins Proteins and MORE Proteins! WOW!
  • 2. Carrier or Transport Proteins- binding site on
    protein surface "grabs" certain molecules and
    pulls them into the cell.

13
Proteins Proteins and MORE Proteins! WOW!
  • 3. Receptor Proteins - molecular triggers that
    set off cell responses (such as release of
    hormones or opening of channel proteins). Must be
    activated on one side of the cell membrane, to
    release something on the other side.

14
Proteins Proteins and MORE Proteins! WOW!
  • 4. Cell Recognition Proteins - ID tags, to
    identify cells to the body's immune system. Very
    similar to security at the dance.

15
The last important Protein for now!
  • 5. Enzymatic Proteins - carry out metabolic
    reactions. There are different protein enzymes
    for every biochemical function in the body. These
    special proteins need to be activated before they
    are turned on.
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