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Transcript
Chapter 2 – The Living Cell
Membrane
1. What are two functions of the cell
membrane?
• The two functions of
the cell membrane are
(1) to separate the cell’s
protoplasm from the
external environment
and (2) to mediate what
substances enter and
leave the cell.
2. What would happen if something
pierced the membrane?
• If the cell membrane is
pierced the protoplasm
would ooze out of the
cell.
• In some cases it is
possible for the
membrane to seal itself
again.
3. What would happen if cells could not
exchange materials with their
environment?
• Cells need to receive
nutrition and gasses from
the external environment
and excrete their wastes.
• If they cannot exchange
materials they would
quickly either die of
starvation or their
metabolic wastes would
poison them.
4. Describe the composition of the cell
membrane.
• The cell membrane is composed of 2 layers of
phospholipid molecules. Each phospholipid
molecule has a hydrophilic “head” and 2
hydrophobic “tails”.
• The hydrophillic heads of one layer face the
external environment and the heads of the
second layer face the internal environment.
• The hydrophobic tails are sandwiched between
the hydrophillic heads.
• A variety of proteins are embedded in the
membrane.
5. Which parts of the cell are
hydrophobic and hydrophillic?
• The polar heads of the
phospholipid molecules
are hyrophillic.
• The tails of the
phospholipid molecules
are hydrophoic.
6. How are phospholipids arranged in
the lipid bilayer?
• The tails of the
phospholipids face
one another and
the polar heads
face the internal
and external
environment.
7. What is a glycoprotein and what
function do they perform for the cell?
• Glycoproteins are
proteins found
embedded in the lipid
bilayer that have a
special sugar molecule
attached.
• They give the cell its
unique identity.
8. Describe the three functions of membrane
proteins.
• Membrane proteins act as “gatekeepers” allowing
substances in and out of the cell.
• They act as receptor sites for hormones.
• They also serve to identify the cell for cell to cell
recognition.
9. How are liposomes used in medicine
today?
• Liposomes are used to
treat cancer.
• They can bind with the
cell membrane and
deliver cancer fighting
drugs directly to the
affected area.
10. What is gene therapy and how is it
linked to liposomes?
• Gene therapy is the
process of introducing new
genes into the DNA of a
person’s cells to correct a
genetic disease or flaw.
• Liposomes can be injected
with the corrected DNA
and they can fuse the to
the target (diseased) cell
and deliver the corrected
DNA.