Opening Questions:

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Opening Questions

• 1. What is the 1st major part of the cell we
  talked about?
• 2. Name one thing that it does for the cell.
• 3. Name the three types of proteins that make up
  the Cytoskeleton.

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Learning Outcomes

• Recognize the key components of the cell plasma
  membrane.
• Explain how the plasma membrane regulates the
  passage f molecules into and out of the cell.
• Describe the diverse functions of proteins
  embedded in the palsma membrane.

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The Three Major Parts of the Cell
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2. PLASMA CELL MEMBRANE
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• It is the protective outer covering of all cells
• It gives the cell its distinct shape
• Acts as a fence around the cell
• Its like a PICKET FENCE

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• Must stay in a SEMI-FLUID state in order to be
  
• SEMI-PERMEABLE or SELECTIVELY PERMEABLE

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SELECTIVELY or SEMI-PERMEABLE

• 1. Allows certain substances in
• Example---Nutrients
• 2. Allows certain substances out
• Example----Waste
• 3. Keeps certain things in
• Example----Organelles
• 4. Keeps certain things out
• Example---Disease and foreign objects

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A. 3 Molecules of the Cell Membrane
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• 1. PHOSPHOLIPID MOLECULE
• Has a head that is made of phosphate
• Hydrophillic
• Water loving
• Because it can dissolve in water

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• It has a tail that is made up of a lipid
• Hydrophobic
• Water fearing
• Because it does not dissolve in water
• Lipids will dissolve in other lipids

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• Because the tail is afraid of H2O and there is
  H2O surrounding your cells.
• Extracellular fluid outside each cell and
• The cytoplasm (made of water and various
  molecules) in each cell
• How do the phospholipid molecules line up?

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• They form a DOUBLE layer with the tails facing
  each other and the heads on the outside and
  inside.

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• Phospholipid molecules act as the
  pickets of the fence
• Little molecules can pass through them by
  dissolving in lipids.

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2. PROTEINS

• Proteins are used to identify large molecules or
  molecules that can not dissolve in lipids.
• Proteins decide whether the larger molecules can
  come in or not

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2 Types of Proteins

• Integral Proteins----
• Proteins that go all the way through the membrane
• 2. Peripheral Proteins---
• Proteins that are only on one side of the membrane

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Proteins act as the gate of the fence
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Membrane Proteins

• a. Channel Proteins
• b. Transport Proteins
• c. Cell Recognition Proteins
• d. Receptor Proteins
• e. Enzymatic Proteins
• f. Junction Proteins

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a. Channel Proteins

• Channel Proteins form a tunnel across the entire
  membrane
• They allow only one or a few specific types of
  molecules to enter or exit the cell.

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EXAMPLE

• Aquaporins---
• Channel proteins in the kidney
• Allows water molecules in or out of the cell
• Without them we would dehydrate

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b. Transport Proteins

• Transport Proteins often bond with a molecule or
  ion and help carry across the membrane.
• They usually use cell energy to help the
  molecule/ion across

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EXAMPLE

• They help sodium and potassium to cross the
  membrane of the nerve cell (neuron)
• Without them, nerve impulses would be impossible.

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c. Cell Recognition Proteins

• Cell Recognition Proteins are glycoproteins that
  are used to enable our bodies to distinguish
  between our own cells and that of another
  organism.

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More Info

• Found especially on white blood cells
• Allow them to distinguish between the pathogens
  that invade our body and our own cells

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d. Receptor Proteins

• Receptor Proteins are proteins that change their
  shape along the membrane which allows a molecule
  known as a SIGNAL MOLECULE to bind to it.

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• The bonding of a signal molecule causes the
  receptor protein to change shape.
• When the receptor protein changes shape the cell
  is able to respond to a certain molecule.

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EXAMPLE

• Hormone insulin binds to the receptor proteins in
  liver cells.
• When they bind to the membrane they allow the
  liver cells to store glucose.

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e. Enzymatic Proteins

• Enzymatic Proteins are proteins that are directly
  involved in the metabolic processes of the cell.
• These proteins can attach to various cell
  membranes

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Example

• DNA helicase---
• Enzyme that causes DNA to unzip (break apart) so
  it can replicate (duplicate)

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f. Junction Proteins

• Junction Proteins are proteins will be discussed
  later.
• But they assist in cell to cell adhesion and
  communication

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More Info

• The cells in the bladder use junction proteins to
  adhere to one another when the bladder fills with
  liquid waste (urine).

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3. CHOLESTEROL

• Another lipid
• Helps to give the cell membrane its shape

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Cholesterol acts as the posts of the fence
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3 major molecules(REVIEW)

• 1. PhosphoLIPID
• Picketssmall things in out
• 2. Proteins---
• Gates---lets big things in out
• 3. Cholesterol---LIPID
• Posts---structure

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• The cell membrane is considered a bilayer or a
  DOUBLE layer of
• PROTEINS and
• LIPIDS

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• Scientists way of describing the cell membrane
• The Fluid
  Mosaic Model

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• FLUID---Because the membrane must stay semi-fluid
  to be selectively permeable
• MOSAIC---Because it is made up of many different
  molecules but is one structure

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Wrap It Up
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• The plasma cell membrane is used as protection
  for each cell--give it distinct shape
• It stays semi fluid---allowing it to be
  selectively permeable

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• This means it selects what goes in and out and
• what stays in and out
• The plasma membrane is made up of 3 main
  molecules
• Phospholipid molecules
• Protein molecules and
• Cholesterol molecules

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• For this reason the plasma (cell) membrane is
  considered a DOUBLE layer of PROTEINS and LIPIDS.