Movement In Vesicles

1
Movement In Vesicles

• Packaged and Distributed

2
Endocytosis

• Many substances such as proteins and
  polysaccharides are too large to be transported
  via carrier proteins.
• These substances must be transported through the
  cell wall by vesicles.
• Endocytosis The movement of a substance into a
  cell by a vesicle.

3
Procedure

• The cell membrane forms a pouch around a
  substance.
• The pouch then closes up and pinches off from the
  cell membrane to form a vesicle.
• It is possible for vesicles to fuse with
  lysosomes or other organelles.

4
Endocytosis Animation

• Endocytosis

5
Exocytosis

• Exocytosis The movement of a substance by a
  vesicle to the outside of a cell.
• During exocytosis, vesicles fuse with the cell
  membrane releasing their contents.
• Cells use exocytosis to export proteins that are
  modified by the Golgi apparatus.

6
Membrane Receptors

• The bodys cells must communicate to coordinate
  growth and development. Cells that do not lie
  next to each other can not communicate directly.
• Cells release signal molecules to carry
  information to nearby cells. Hormones are a
  familiar example of this cellular signaling.

7
Receptor Proteins

• Cells must have a way to filter out the
  unimportant and respond to the important
  messages.
• Special proteins that bind to signal molecules
  are called Receptor Proteins.
• The receptor proteins are specific to the type of
  signal molecules they bind to.

8
Function of Receptor Proteins

• A signal molecule is bound by a receptor protein
  that fits the molecule.
• Receptor proteins are embedded in the lipid
  bilayer of the cell membrane.
• The part of the protein that binds to the signal
  molecule faces the outside of the cell.
• The binding of a signal molecule by its
  complementary protein causes a change in the
  receiving cell.

9
Changes

• There are three possible changes in the cell.
• The permeability of the receiving cell changes.
• A second messenger can be formed inside the cell.
• Enzymes may be activated inside the cell.

10
Permeability Changes

• The receptor may be coupled with an ion channel.
  The binding of a signal molecule to the receptor
  protein causes the ion channel to open.
• This allows specific ions to cross the cell
  membrane.

11
Second Messengers

• The receptor protein may signal the formation of
  another messenger within the cell.
• When it is activated, the second messenger acts
  as a signal molecule in the cytoplasm of the
  cell. It amplifies the message of the first
  messenger.
• This can change the function of the cell by
  activating enzymes or triggering biochemical
  reactions

12
Enzyme Action

• The receptor protein may act as an enzyme.
• When a signal molecule binds to the receptor
  protein, the receptor may speed up chemical
  reactions inside the cell.
• Receptor proteins may also activate other enzymes
  located inside the cell to trigger biochemical
  reactions in the cell.